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  • 1.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Karlsson Andersson, M.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khosrawi, Farahnaz
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    On the linkage between tropospheric and Polar Stratospheric clouds in the Arctic as observed by space-borne lidar2012In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 12, no 8, p. 3791-3798Article in journal (Refereed)
    Abstract [en]

    The type of Polar stratospheric clouds (PSCs) as well as their temporal and spatial extent are important for the occurrence of heterogeneous reactions in the polar stratosphere. The formation of PSCs depends strongly on temperature. However, the mechanisms of the formation of solid PSCs are still poorly understood. Recent satellite studies of Antarctic PSCs have shown that their formation can be associated with deep-tropospheric clouds which have the ability to cool the lower stratosphere radiatively and/or adiabatically. In the present study, lidar measurements aboard the Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observation (CALIPSO) satellite were used to investigate whether the formation of Arctic PSCs can be associated with deep-tropospheric clouds as well. Deep-tropospheric cloud systems have a vertical extent of more than 6.5 km with a cloud top height above 7 km altitude. PSCs observed by CALIPSO during the Arctic winter 2007/2008 were classified according to their type (STS, NAT, or ice) and to the kind of underlying tropospheric clouds. Our analysis reveals that 172 out of 211 observed PSCs occurred in connection with tropospheric clouds. 72% of these 172 observed PSCs occurred above deep-tropospheric clouds. We also find that the type of PSC seems to be connected to the characteristics of the underlying tropospheric cloud system. During the Arctic winter 2007/2008 PSCs consisting of ice were mainly observed in connection with deep-tropospheric cloud systems while no ice PSC was detected above cirrus. Furthermore, we find no correlation between the occurrence of PSCs and the top temperature of tropospheric clouds. Thus, our findings suggest that Arctic PSC formation is connected to adiabatice cooling, i.e. dynamic effects rather than radiative cooling.

  • 2.
    Achtert, Peggy
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khosrawi, Farahnaz
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Pure rotational-Raman channels of the Esrange lidar for temperature and particle extinction measurements in the troposphere and lower stratosphere2013In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 6, no 1, p. 91-98Article in journal (Refereed)
    Abstract [en]

    The Department of Meteorology at Stockholm University operates the Esrange Rayleigh/Raman lidar at Esrange(68° N, 21° E) near the Swedish city of Kiruna. This paper describes the design and first measurements of the newpure rotational-Raman channel of the Esrange lidar. The Esrange lidar uses a pulsed Nd:YAG solid-state laser operating at 532 nm as light source with a repetition rate of 20 Hz and a pulse energy of 350 mJ. The minimum vertical resolution is 150m and the integration time for one profile is 5000 shots. The newly implemented channel allows for measurements of atmospheric temperature at altitudes below 35 km and is currently optimized for temperature measurements between 180 and 200 K. This corresponds to conditions in the lower Arctic stratosphere during winter. In addition to the temperature measurements, the aerosol extinction coefficientand the aerosol backscatter coefficient at 532 nm can be measured in dependently. Our filter-based design minimizes the systematic error in the obtained temperature profile to less than 0.51 K. By combining rotational-Raman measurements (5–35 km height) and the integration technique (30–80 kmheight), the Esrange lidar is now capable of measuring atmospheric temperature profiles from the upper troposphere up to the mesosphere. With the improved setup, the system can be used to validate current lidar-based polar stratospheric cloud classification schemes. The new capability of the instrument measuring temperature and aerosol extinction furthermore enables studies of the thermal structure and variability of the upper troposphere/lower stratosphere. Although several lidars are operated at polar latitudes, there are few instruments that are capable of measuring temperature profiles in the troposphere, stratosphere, and mesosphere, as well as aerosols extinction in the troposphere and lower stratospherewith daylight capability.

  • 3. Amyx, K.
    et al.
    Sternovsky, Z.
    Knappmiller, S.
    Robertson, S.
    Horanyi, M.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology.
    In-situ measurement of smoke particles in the wintertime polar mesosphere between 80 and 85 km altitude2008In: Journal of Atmospheric and Solar-Terrestrial Physics, Vol. 70, p. 61-70Article in journal (Refereed)
    Abstract [en]

    The MAGIC sounding rocket, launched in January 2005 into the polar mesosphere, carried two detectors for charged aerosol particles. The detectors are graphite patch collectors mounted flush with the skin of the payload and are connected to sensitive electrometers. The measured signal is the net current deposited on the detectors by heavy aerosol particles. The collection of electrons and ions is prevented by magnetic shielding and a small positive bias, respectively. Both instruments detected a layer of heavy aerosol particles between 80 and 85 km with a number density approximately 103 cm−3. Aerodynamic flow simulations imply that the collected particles are larger than 1 nm in radius. The particles are detected as a net positive charge deposited on the graphite collectors. It is suggested that the measured positive polarity is due to the electrification of the smoke particles upon impact on the graphite collectors.

  • 4. Belova, E.
    et al.
    Kirkwood, S.
    Latteck, R.
    Zecha, M.
    Pinedo, H.
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Multi-radar observations of polar mesosphere summer echoes during the PHOCUS campaign on 20-22 July 20112014In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 118, p. 199-205Article in journal (Refereed)
    Abstract [en]

    During the PHOCUS rocket campaign, on 20-22 July 2011, the observations of polar mesosphere summer echoes (PMSE) were made by three mesosphere-stratosphere-troposphere radars, operating at about 50 MHz. One radar, ESRAD is located at Esrange in Sweden, where the rocket was launched, two other radars, MAARSY and MORRO, are located 250 km north-west and 200 km north of the ESRAD, respectively, on the other side of the Scandinavian mountain ridge. We compared PMSE as measured by these three radars in terms of their strength, spectral width and wave modulation. Time-altitude maps of PMSE strength look very similar for all three radars. Cross-correlations with maximum values 0.5-0.6 were found between the signal powers over the three days of observations for each pair of radars. By using cross-spectrum analysis of PMSE signals, we show that some waves with periods of a few hours were observed by all three radars. Unlike the strengths, simultaneous values of PMSE spectral width, which is related to turbulence, sometimes differ significantly between the radars. For interpretation of the results we suggested that large-scale fields of neutral temperature, ice particles and electron density, which are more or less uniform over 150-250 km horizontal extent were 'modulated' by waves and smaller patches of turbulence.

  • 5.
    Benze, Susanne
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology . University of Colorado, USA.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Randall, Cora E.
    Karlsson, Bodil
    Stockholm University, Faculty of Science, Department of Meteorology .
    Hultgren, Kristoffer
    Stockholm University, Faculty of Science, Department of Meteorology .
    Lumpe, Jerry D.
    Baumgarten, Gerd
    Making limb and nadir measurements comparable: A common volume study of PMC brightness observed by Odin OSIRIS and AIM CIPS2018In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 167, p. 66-73Article in journal (Refereed)
    Abstract [en]

    Combining limb and nadir satellite observations of Polar Mesospheric Clouds (PMCs) has long been recognized as problematic due to differences in observation geometry, scattering conditions, and retrieval approaches. This study offers a method of comparing PMC brightness observations from the nadir-viewing Aeronomy of Ice in the Mesosphere (AIM) Cloud Imaging and Particle Size (CIPS) instrument and the limb-viewing Odin Optical Spectrograph and InfraRed Imaging System (OSIRIS). OSIRIS and CIPS measurements are made comparable by defining a common volume for overlapping OSIRIS and CIPS observations for two northern hemisphere (NH) PMC seasons: NH08 and NH09. We define a scattering intensity quantity that is suitable for either nadir or limb observations and for different scattering conditions. A known CIPS bias is applied, differences in instrument sensitivity are analyzed and taken into account, and effects of cloud inhomogeneity and common volume definition on the comparison are discussed. Not accounting for instrument sensitivity differences or inhomogeneities in the PMC field, the mean relative difference in cloud brightness (CIPS - OSIRIS) is -102 +/- 55%. The differences are largest for coincidences with very inhomogeneous clouds that are dominated by pixels that CIPS reports as non-cloud points. Removing these coincidences, the mean relative difference in cloud brightness reduces to -6 +/- 14%. The correlation coefficient between the CIPS and OSIRIS measurements of PMC brightness variations in space and time is remarkably high, at 0.94. Overall, the comparison shows excellent agreement despite different retrieval approaches and observation geometries.

  • 6.
    Broman, Lina
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Benze, Susanne
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Christensen, Ole Martin
    Stockholm University, Faculty of Science, Department of Meteorology .
    Randall, Cora E.
    Common volume satellite studies of polar mesospheric clouds with Odin/OSIRIS tomography and AIM/CIPS nadir imaging2019In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 19, no 19, p. 12455-12475Article in journal (Refereed)
    Abstract [en]

    Two important approaches for satellite studies of polar mesospheric clouds (PMCs) are nadir measurements adapting phase function analysis and limb measurements adapting spectroscopic analysis. Combining both approaches enables new studies of cloud structures and microphysical processes but is complicated by differences in scattering conditions, observation geometry and sensitivity. In this study, we compare common volume PMC observations from the nadir-viewing Cloud Imaging and Particle Size (CIPS) instrument on the Aeronomy of Ice in the Mesosphere (AIM) satellite and a special set of tomographic limb observations from the Optical Spectrograph and InfraRed Imager System (OSIRIS) on the Odin satellite performed over 18 d for the years 2010 and 2011 and the latitude range 78 to 80 degrees N. While CIPS provides preeminent horizontal resolution, the OSIRIS tomographic analysis provides combined horizontal and vertical PMC information. This first direct comparison is an important step towards co-analysing CIPS and OSIRIS data, aiming at unprecedented insights into horizontal and vertical cloud processes. Important scientific questions on how the PMC life cycle is affected by changes in humidity and temperature due to atmospheric gravity waves, planetary waves and tides can be addressed by combining PMC observations in multiple dimensions. Two- and three-dimensional cloud structures simultaneously observed by CIPS and tomographic OSIRIS provide a useful tool for studies of cloud growth and sublimation Moreover, the combined CIPS/tomographic OSIRIS dataset can be used for studies of even more fundamental character, such as the question of the assumption of the PMC particle size distribution. We perform the first thorough error characterization of OSIRIS tomographic cloud brightness and cloud ice water content (IWC). We establish a consistent method for comparing cloud properties from limb tomography and nadir observations, accounting for differences in scattering conditions, resolution and sensitivity. Based on an extensive common volume and a temporal coincidence criterion of only 5 min, our method enables a detailed comparison of PMC regions of varying brightness and IWC. However, since the dataset is limited to 18 d of observations this study does not include a comparison of cloud frequency. The cloud properties of the OSIRIS tomographic dataset are vertically resolved, while the cloud properties of the CIPS dataset is vertically integrated. To make these different quantities comparable, the OSIRIS tomographic cloud properties cloud scattering coefficient and ice mass density (IMD) have been integrated over the vertical extent of the cloud to form cloud albedo and IWC of the same quantity as CIPS cloud products. We find that the OSIRIS albedo (obtained from the vertical integration of the primary OSIRIS tomography product, cloud scattering coefficient) shows very good agreement with the primary CIPS product, cloud albedo, with a correlation coefficient of 0.96. However, OSIRIS systematically reports brighter clouds than CIPS and the bias between the instruments (OSIRIS -CIPS) is 3.4 x 10(-6) sr(-1) (+/- 2.9x 10(-6) sr(-1)) on average. The OSIRIS tomography IWC (obtained from the vertical integration of IMD) agrees well with the CIPS IWC, with a correlation coefficient of 0.91. However, the IWC reported by OSIRIS is lower than CIPS, and we quantify the bias to -22 g km(-2) (+/- 14 g km(-2)) on average.

  • 7. Christensen, O. M.
    et al.
    Eriksson, P.
    Urban, J.
    Murtagh, D.
    Hultgren, Kristoffer
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Tomographic retrieval of water vapour and temperature around polar mesospheric clouds using Odin-SMR2015In: atmospheric measurement techniques, ISSN 1867-1381, Vol. 8, no 5, p. 1981-1999Article in journal (Refereed)
    Abstract [en]

    A special observation mode of the Odin satellite provides the first simultaneous measurements of water vapour, temperature and polar mesospheric cloud (PMC) brightness over a large geographical area while still resolving both horizontal and vertical structures in the clouds and background atmosphere. The observation mode was activated during June, July and August of 2010 and 2011, and for latitudes between 50 and 82 degrees N. This paper focuses on the water vapour and temperature measurements carried out with Odin's sub-millimetre radiometer (SMR). The tomographic retrieval approach used provides water vapour and temperature between 75 and 90 km with a vertical resolution of about 2.5 km and a horizontal resolution of about 200 km. The precision of the measurements is estimated to 0.2 ppmv for water vapour and 2K for temperature. Due to limited information about the pressure at the measured altitudes, the results have large uncertainties (> 3 ppmv) in the retrieved water vapour. These errors, however, influence mainly the mean atmosphere retrieved for each orbit, and variations around this mean are still reliably captured by the measurements. SMR measurements are performed using two different mixer chains, denoted as frequency mode 19 and 13. Systematic differences between the two frontends have been noted. A first comparison with the Solar Occultation For Ice Experiment instrument (SOFIE) on-board the Aeronomy of Ice in the Mesosphere (AIM) satellite and the Fourier Transform Spectrometer of the Atmospheric Chemistry Experiment (ACE-FTS) on-board SCISAT indicates that the measurements using the frequency mode 19 have a significant low bias in both temperature (> 15 K) and water vapour (> 0.5 ppmv), while the measurements using frequency mode 13 agree with the other instruments considering estimated errors. PMC brightness data is provided by OSIRIS, Odin's other sensor. Combined SMR and OSIRIS data for some example orbits is considered. For these orbits, effects of PMCs on the water vapour distribution are clearly seen. Areas depleted of water vapour are found above layers with PMC, while regions of enhanced water vapour due to ice particle sedimentation are primarily placed between and under the clouds.

  • 8.
    Christensen, Ole Martin
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Benze, Susanne
    Stockholm University, Faculty of Science, Department of Meteorology .
    Eriksson, Patrick
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Megner, Linda
    Stockholm University, Faculty of Science, Department of Meteorology .
    Murtagh, Donal P.
    The relationship between polar mesospheric clouds and their background atmosphere as observed by Odin-SMR and Odin-OSIRIS2016In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 16, no 19, p. 12587-12600Article in journal (Refereed)
    Abstract [en]

    In this study the properties of polar mesospheric clouds (PMCs) and the background atmosphere in which they exist are studied using measurements from two instruments, OSIRIS and SMR, on board the Odin satellite. The data comes from a set of tomographic measurements conducted by the satellite during 2010 and 2011. The expected ice mass density and cloud frequency for conditions of thermodynamic equilibrium, calculated using the temperature and water vapour as measured by SMR, are compared to the ice mass density and cloud frequency as measured by OSIRIS. We find that assuming thermodynamic equilibrium reproduces the seasonal, latitudinal and vertical variations in ice mass density and cloud frequency, but with a high bias of a factor of 2 in ice mass density. To investigate this bias, we use a simple ice particle growth model to estimate the time it would take for the observed clouds to sublimate completely and the time it takes for these clouds to reform. We find a difference in the median sublimation time (1.8 h) and the reformation time (3.2 h) at peak cloud altitudes (82-84 km). This difference implies that temperature variations on these timescales have a tendency to reduce the ice content of the clouds, possibly explaining the high bias of the equilibrium model. Finally, we detect and are, for the first time, able to positively identify cloud features with horizontal scales of 100 to 300 km extending far below the region of supersaturation (>2 km). Using the growth model, we conclude these features cannot be explained by sedimentation alone and suggest that these events may be an indication of strong vertical transport.

  • 9. Dawkins, E. C. M.
    et al.
    Plane, J. M. C.
    Chipperfield, M. P.
    Feng, W.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Höffner, J.
    Friedman, J. S.
    First global observations of the mesospheric potassium layer2014In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 41, no 15, p. 5653-5661Article in journal (Refereed)
    Abstract [en]

    Metal species, produced by meteoric ablation, act as useful tracers of upper atmosphere dynamics and chemistry. Of these meteoric metals, K is an enigma: at extratropical latitudes, limited available lidar data show that the K layer displays a semiannual seasonal variability, rather than the annual pattern seen in other metals such as Na and Fe. Here we present the first near-global K retrieval, where K atom number density profiles are derived from dayglow measurements made by the Optical Spectrograph and Infrared Imager System spectrometer on board the Odin satellite. This robust retrieval produces density profiles with typical layer peak errors of 15% and a 2km vertical grid resolution. We demonstrate that these retrieved profiles compare well with available lidar data and show for the first time that the unusual semiannual behavior is near-global in extent. This new data set has wider applications for improving understanding of the K chemistry and of related upper atmosphere processes.

  • 10. Eberhart, Martin
    et al.
    Löhle, Stefan
    Strelnikov, Boris
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Fasoulas, Stefanos
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Lübken, Franz-Josef
    Rapp, Markus
    Atomic oxygen number densities in the mesosphere-lower thermosphere region measured by solid electrolyte sensors on WADIS-22019In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 12, no 4, p. 2445-2461Article in journal (Refereed)
    Abstract [en]

    Absolute profiles of atomic oxygen number densities with high vertical resolution have been determined in the mesosphere-lower thermosphere (MLT) region from in situ measurements by several rocket-borne solid electrolyte sensors. The amperometric sensors were operated in both controlled and uncontrolled modes and with various orientations on the foredeck and aft deck of the payload. Calibration was based on mass spectrometry in a molecular beam containing atomic oxygen produced in a microwave discharge. The sensor signal is proportional to the number flux onto the electrodes, and the mass flow rate in the molecular beam was additionally measured to derive this quantity from the spectrometer reading. Numerical simulations provided aerodynamic correction factors to derive the atmospheric number density of atomic oxygen from the sensor data. The flight results indicate a preferable orientation of the electrode surface perpendicular to the rocket axis. While unstable during the upleg, the density profiles measured by these sensors show an excellent agreement with the atmospheric models and photometer results during the downleg of the trajectory. The high spatial resolution of the measurements allows for the identification of small-scale variations in the atomic oxygen concentration.

  • 11.
    Ehard, Benedikt
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Achtert, Peggy
    Stockholm University, Faculty of Science, Department of Meteorology .
    Dörnbrack, Andreas
    Gisinger, Sonja
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Rapp, Markus
    Wagner, Johannes
    Combination of Lidar and Model Data for Studying Deep Gravity Wave Propagation2016In: Monthly Weather Review, ISSN 0027-0644, E-ISSN 1520-0493, Vol. 144, no 1, p. 77-98Article in journal (Refereed)
    Abstract [en]

    The paper presents a feasible method to complement ground-based middle atmospheric Rayleigh lidar temperature observations with numerical simulations in the lower stratosphere and troposphere to study gravity waves. Validated mesoscale numerical simulations are utilized to complement the temperature below 30-km altitude. For this purpose, high-temporal-resolution output of the numerical results was interpolated on the position of the lidar in the lee of the Scandinavian mountain range. Two wintertime cases of orographically induced gravity waves are analyzed. Wave parameters are derived using a wavelet analysis of the combined dataset throughout the entire altitude range from the troposphere to the mesosphere. Although similar in the tropospheric forcings, both cases differ in vertical propagation. The combined dataset reveals stratospheric wave breaking for one case, whereas the mountain waves in the other case could propagate up to about 40-km altitude. The lidar observations reveal an interaction of the vertically propagating gravity waves with the stratopause, leading to a stratopause descent in both cases.

  • 12.
    Ehard, Benedikt
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Achtert, Peggy
    Stockholm University, Faculty of Science, Department of Meteorology . Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Long-term lidar observations of wintertime gravity wave activity over northern Sweden2014In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 32, no 11, p. 1395-1405Article in journal (Refereed)
    Abstract [en]

    This paper presents an analysis of gravity wave activity over northern Sweden as deduced from 18 years of wintertime lidar measurements at Esrange (68ºN, 21ºE). Gravity wave potential energy density (GWPED) was used to characterize the strength of gravity waves in the altitude regions 30–40km and 40–50 km. The obtained values ex- ceed previous observations reported in the literature. This is suggested to be due to Esrange’s location downwind of the Scandinavian mountain range and due to differences in the various methods that are currently used to retrieve gravity wave parameters. The analysis method restricted the identification of the dominating vertical wavelengths to a range from 2 to 13 km. No preference was found for any wavelength in this window. Monthly mean values of GW- PED show that most of the gravity waves’ energy dissipates well below the stratopause and that higher altitude regions show only small dissipation rates of GWPED. Our analy- sis does not reproduce the previously reported negative trend in gravity wave activity over Esrange. The observed inter-annual variability of GWPED is connected to the occurrence of stratospheric warmings with generally lower wintertime mean GWPED during years with major stratospheric warmings. A bimodal GWPED occurrence frequency indicates that gravitywave activity at Esrange is affected by both ubiq- uitous wave sources and orographic forcing.

  • 13. Fan, Z.Y.
    et al.
    Plane, J.M.C.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology.
    On the global distribution of sporadic sodium layers2007In: Geophysical Research Letters, ISSN 0094-8276, Vol. 34, no 15, p. L15808-Article in journal (Refereed)
  • 14. Fan, Z.Y.
    et al.
    Plane, J.M.C.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology.
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology.
    Llewellyn, E.J.
    Satellite measurements of the global mesospheric sodium layer2007In: Atmospheric Chemistry and Physics, ISSN 1680-7316, Vol. 7, no 15, p. 4107-4115Article in journal (Refereed)
  • 15. Grygalashvyly, Mykhaylo
    et al.
    Eberhart, Martin
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Strelnikov, Boris
    Lübken, Franz-Josef
    Rapp, Markus
    Löhle, Stefan
    Fasoulas, Stefanos
    Khaplanova, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Vorobeva, Ekaterina
    Atmospheric band fitting coefficients derived from a self-consistent rocket-borne experiment2019In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 19, no 2, p. 1207-1220Article in journal (Refereed)
    Abstract [en]

    Based on self-consistent rocket-borne measurements of temperature, the densities of atomic oxygen and neutral air, and the volume emission of the atmospheric band (762 nm), we examined the one-step and two-step excitation mechanism of O-2 (b(1)Sigma(+)(g)) for nighttime conditions. Following McDade et al. (1986), we derived the empirical fitting coefficients, which parameterize the atmospheric band emission O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(g)) (0, 0). This allows us to derive the atomic oxygen concentration from nighttime observations of atmospheric band emission O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(g)) (0, 0). The derived empirical parameters can also be utilized for atmospheric band modeling. Additionally, we derived the fit function and corresponding coefficients for the combined (one-and two-step) mechanism. The simultaneous common volume measurements of all the parameters involved in the theoretical calculation of the observed O-2 (b(1)Sigma(+)(g) - X-3 Sigma(-)(g)) (0, 0) emission, i.e., temperature and density of the background air, atomic oxygen density, and volume emission rate, is the novelty and the advantage of this work.

  • 16. Guineva, V.
    et al.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Werner, R.
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Neichev, S.
    Kirov, B.
    Bankov, L.
    Gramatikov, P.
    Tashev, V.
    Popov, M.
    Hauglund, K.
    Hansen, G.
    Ilstad, J.
    Wold, H.
    O-2 density and temperature profiles retrieving from direct solar Lyman-alpha radiation measurements2009In: Geomagnetism and Aeronomy, ISSN 0016-7932, E-ISSN 1555-645X, Vol. 49, no 8, p. 1292-1295Article in journal (Refereed)
    Abstract [en]

    The resonance transition P-2-S-2 of the atomic hydrogen (Lyman-alpha emission) is the strongest and most conspicuous feature in the solar EUV spectrum. The Lyman-alpha radiation transfer depends on the resonance scattering from the hydrogen atoms in the atmosphere and on the O-2 absorption. Since the Lyman-alpha extinction in the atmosphere is a measure for the column density of the oxygen molecules, the atmospheric O-2 density and temperature profiles can be calculated thereof. A detector of solar Lyman-alpha radiation was manufactured in the Stara Zagora Department of the Solar-Terrestrial Influences Laboratory (STIL). Its basic part is an ionization camera, filled in with NO. A 60 V power supply is applied to the chamber. The produced photoelectric current from the sensor is fed to a two-channel amplifier, providing analog signal. The characteristics of the Lyman-alpha detector were studied. It passed successfully all tests and the results showed that the so-designed instrument could be used in rocket experiments to measure the Lymanalpha flux. From the measurements of the detector, the Lyman-alpha vertical profile can be obtained. Programs are created to compute the O-2 density, atmospheric power and temperature profiles based on Lymanalpha data. The detector design appertained to ASLAF project (Attenuation of the Solar Lyman-Alpha Flux), a scientific cooperation between STIL-Bul.Acad.Sci., Stara Zagora Department and the Atmospheric Physics Group at the Department of Meteorology (MISU), Stockholm University, Sweden. The joint project was part of the rocket experiment HotPay I, in the ALOMAR eARI Project, EU's 6th Framework Programme, Andoya Rocket Range, Andenes, Norway. The project is partly financed by the Bulgarian Ministry of Science and Education.

  • 17.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology.
    Fan, Z. Y.
    Wademarsson, Tomas
    Stockholm University, Faculty of Science, Department of Meteorology.
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology.
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology.
    Llewellyn, E. J.
    She, C.-Y.
    Plane, J. M. C.
    Retrieval of the global mesopsheric sodium density from the Odin satellite2007In: Geophysical Research Letters, Vol. 34, no L04813Article in journal (Refereed)
    Abstract [en]

    Satellite observations of the Na D dayglow at 589 nm provide a global database for the climatology of the mesospheric sodium layer. More than five years of Na D limb observations are available from the Optical Spectrograph and InfraRed Imager System onboard the Odin satellite. We describe a robust retrieval method that provides individual sodium density profiles with a typical accuracy of 20% and altitude resolution of 2 km. Retrieved column abundances and density profiles are validated against sodium resonance lidar measurements at mid-latitudes. Examples of the seasonal and latitudinal variation of the sodium layer illustrate Odin's potential for climatological studies of mesospheric metals.

  • 18.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Fan, Z. Y.
    Waldemarsson, T.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Llewellyn, E. J.
    She, C. -Y
    Plane, J. M. C.
    Retrieval of global mesospheric sodium densities from the Odin satellite2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 4, p. L04813-Article in journal (Refereed)
    Abstract [en]

    Satellite observations of the Na D dayglow at 589 nm provide a global database for the climatology of the mesospheric sodium layer. More than five years of Na D limb observations are available from the Optical Spectrograph and InfraRed Imager System onboard the Odin satellite. We describe a robust retrieval method that provides individual sodium density profiles with a typical accuracy of 20% and altitude resolution of 2 km. Retrieved column abundances and density profiles are validated against sodium resonance lidar measurements at mid- latitudes. Examples of the seasonal and latitudinal variation of the sodium layer illustrate Odin's potential for climatological studies of mesospheric metals.

  • 19.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Hultgren, Kristoffer
    Stockholm University, Faculty of Science, Department of Meteorology .
    Mesospheric Airglow/Aerosol Tomography and Spectroscopy (MATS) - a satellite mission on mesospheric wavesManuscript (preprint) (Other academic)
  • 20.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Körnich, Heiner
    Stockholm University, Faculty of Science, Department of Meteorology .
    Bailey, S. M.
    Lubken, F. -J
    Morris, R.
    Special issue on layered phenomena in the mesopause region Foreword2011In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 73, no 14-15, p. 2045-2048Article in journal (Refereed)
  • 21.
    Gumbel, Jörg
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Megner, Linda
    Stockholm University, Faculty of Science, Department of Meteorology .
    Charged meteoric smoke as ice nuclei in the mesosphere. Part 1: A review of basic concepts2009In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 71, no 12, p. 1225-1235Article in journal (Refereed)
    Abstract [en]

    The role of meteoric smoke as condensation nuclei for mesospheric ice has recently been challenged by model simulations on the global transport of meteoric material. At the same time a considerable fraction of smoke particles is charged in the mesosphere. This has significant effects on nucleation processes as it can remove the Kelvin barrier. We suggest that in particular nucleation on negatively charged smoke is likely to be a dominant mechanism for mesospheric ice formation. This is in contrast to nucleation on positive ion clusters as the latter is largely hampered by efficient ion/electron recombination. Surprisingly, the large potential of nucleation on charged smoke has so far not been considered in mesospheric ice models. A challenging question concerns the fraction of mesospheric smoke that is actually charged. An improved understanding of mesospheric charging and nucleation will require laboratory experiments on nuclei in the transition regime between molecular and particulate sizes.

  • 22. Havnes, O.
    et al.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Antonsen, T.
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    La Hoz, C.
    On the size distribution of collision fragments of NLC dust particles and their relevance to meteoric smoke particles2014In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 118, p. 190-198Article in journal (Refereed)
    Abstract [en]

    We present the results from a new dust probe MUDD on the PHOCUS payload which was launched in July 2011. In the interior of MUDD all the incoming NLC/PMSE icy dust particles will collide, at an impact angle similar to 70 degrees to the surface normal, with a grid constructed such that no dust particles can directly hit the bottom plate of the probe. Only collision fragments will continue down towards the bottom plate. We determine an energy distribution of the charged fragments by applying a variable electric field between the impact grid and the bottom plate of MUDD. We find that similar to 30% of the charged fragments have kinetic energies less than 10 eV, similar to 20% have energies between 10 and 20 eV while similar to 50% have energies above 20 eV. The transformation of limits in kinetic energy for ice or meteoric smoke particles (MSP) to radius is dependent on many assumptions, the most crucial being fragment velocity. We find, however, that the sizes of the charged fragments most probably are in the range of 1 to 2 nm if meteoric smoke particles (MSP), and slightly higher if ice particles. The observed high charging fraction and the dominance of fragment sizes below a few nm makes it very unlikely that the fragments can consist mainly of ice but that they must be predominantly MSP as predicted by Havnes and N ae sheim (2007) and recently observed by Hervig et al. (2012). The MUDD results indicate that MSP are embedded in NLC/PMSE ice particles with a minimum volume filling factor of similar to.05% in the unlikely case that all embedded MSP are released and charged. A few % volume filling factor (Hervig et al., 2012) can easily be reached if similar to 10% of the MSP are released and that their charging probability is similar to 0.1.

  • 23.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Giovane, Frank
    Waldemarsson, Tomas
    Stockholm University, Faculty of Science, Department of Meteorology . Naval Research Laboratory, USA.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Blum, Jürgen
    Stroud, Rhonda M.
    Marlin, Layne
    Moser, John
    Siskind, David E.
    Jansson, Kjell
    Stockholm University, Faculty of Science, Department of Materials and Environmental Chemistry (MMK).
    Saunders, Russell W.
    Summers, Michael E.
    Reissaus, Philipp
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Plane, John M. C.
    Horanyi, Mihaly
    The MAGIC meteoric smoke particle sampler2014In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 118, p. 127-144Article in journal (Refereed)
    Abstract [en]

    Between a few tons to several hundred tons of meteoric material enters the Earth's atmosphere each day, and most of this material is ablated and vaporized in the 70-120 km altitude region. The subsequent chemical conversion, re-condensation and coagulation of this evaporated material are thought to form nanometre sized meteoric smoke particles (MSPs). These smoke particles are then subject to further coagulation, sedimentation and global transport by the mesospheric circulation. MSPs have been proposed as a key player in the formation and evolution of ice particle layers around the mesopause region, i.e. noctilucent clouds (NLC) and polar mesosphere summer echoes (PMSE). MSPs have also been implicated in mesospheric heterogeneous chemistry to influence the mesospheric odd oxygen/odd hydrogen (O-x/HOx) chemistry, to play an important role in the mesospheric charge balance, and to be a significant component of stratospheric aerosol and enhance the depletion of O-3. Despite their apparent importance, little is known about the properties of MSPs and none of the hypotheses can be verified without direct evidence of the existence, altitude and size distribution, shape and elemental composition. The aim of the MAGIC project (Mesospheric Aerosol - Genesis, Interaction and Composition) was to develop an instrument and analysis techniques to sample for the first time MSPs in the mesosphere and return them to the ground for detailed analysis in the laboratory. MAGIC meteoric smoke particle samplers have been flown on several sounding rocket payloads between 2005 and 2011. Several of these flights concerned non-summer mesosphere conditions when pure MSP populations can be expected. Other flights concerned high latitude summer conditions when MSPs are expected to be contained in ice particles in the upper mesosphere. In this paper we present the MAGIC project and describe the MAGIC MSP sampler, the measurement procedure and laboratory analysis. We also present the attempts to retrieve MSPs from these flights, the challenges inherent to the sampling of nanometre sized particles and the subsequent analysis of the sampled material, and thoughts for the future. Despite substantial experimental efforts, the MAGIC project has so far failed to provide conclusive results. While particles with elemental composition similar to what is to be expected from MSPs have been found, the analysis has been compromised by challenges with different types of contamination and uncertainties in the sticking efficiency of the particles on the sampling surfaces.

  • 24.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    The global mesospheric sodium layer observed by Odin/OSIRIS in 2004-20092011In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 73, no 14-15, p. 2221-2227Article in journal (Refereed)
    Abstract [en]

    The source of the mesospheric sodium layer is the daily ablation of 10-100 tons of meteoric material in Earth's atmosphere. Global studies of this layer yield important information about the chemistry and dynamics of Earth's mesosphere and lower thermosphere (MLT). For nine years the Optical Spectrograph and Infra-Red Imager System (OSIRIS) on-board the Odin satellite has observed Earth's middle atmosphere by limb measurements of scattered sunlight from the ultraviolet to the infrared. In its aeronomy mode, Odin performs limb scans during 15 near-polar sun-synchronous orbits each day. The current measurement programme provides scans up to 110 km on about 300 days per year. Above 70 km, Na D resonance scattering at 589 nm results in a strong limb signal. Retrievals from this dayglow feature have provided a global database of the mesospheric sodium layer. We present an updated sodium climatology from the Odin mission, including latitudinal and seasonal dependence, and interannual variability. We find a weak seasonal variation at low latitudes and an annual variation at mid- and high-latitudes with a clear summer minimum. An interesting feature is an interhemispheric asymmetry in the global dataset with larger sodium abundances during fall in the northern hemisphere and during spring in the southern hemisphere.

  • 25.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Optical studies of noctilucent clouds in the extreme ultraviolet2008In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 26, no 5, p. 1109-1119Article in journal (Refereed)
    Abstract [en]

    In order to better understand noctilucent clouds (NLC) and their sensitivity to the variable environment of the polar mesosphere, more needs to be learned about the actual cloud particle population. Optical measurements are today the only means of obtaining information about the size of mesospheric ice particles. In order to efficiently access particle sizes, scattering experiments need to be performed in the Mie scattering regime, thus requiring wavelengths of the order of the particle size. Previous studies of NLC have been performed at wavelengths down to 355 nm from the ground and down to about 200 nm from rockets and satellites. However, from these measurements it is not possible to access the smaller particles in the mesospheric ice population. This current lack of knowledge is a major limitation when studying important questions about the nucleation and growth processes governing NLC and related particle phenomena in the mesosphere. We show that NLC measurements in the extreme ultraviolet, in particular using solar Lyman-α radiation at 121.57 nm, are an efficient way to further promote our understanding of NLC particle size distributions. This applies both to global measurements from satellites and to detailed in situ studies from sounding rockets. Here, we present examples from recent rocket-borne studies that demonstrate how ambiguities in the size retrieval at longer wavelengths can be removed by invoking Lyman-α. We discuss basic requirements and instrument concepts for future rocket-borne NLC missions. In order for Lyman-α radiation to reach NLC altitudes, high solar elevation and, hence, daytime conditions are needed. Considering the effects of Lyman-α on NLC in general, we argue that the traditional focus of rocket-borne NLC missions on twilight conditions has limited our ability to study the full complexity of the summer mesopause environment.

  • 26.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Rapp, Markus
    On the efficiency of rocket-borne particle detection in the mesosphere2007In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 7, no 14, p. 3701-3711Article in journal (Refereed)
    Abstract [en]

    Meteoric smoke particles have been proposed as a key player in the formation and evolution of mesospheric phenomena. Despite their apparent importance still very little is known about these particles. Important questions concern the smoke number density and size distribution as a function of altitude as well as the fraction of charged particles. Sounding rockets are used to measure smoke in situ, but aerodynamics has remained a major challenge. Basically, the small smoke particles tend to follow the gas flow around the payload rather than reaching the detector if aerodynamics is not considered carefully in the detector design. So far only indirect evidence for the existence of meteoric smoke has been available from measurements of heavy charge carriers. Quantitative ways are needed that relate these measured particle population to the atmospheric particle population. This requires in particular knowledge about the size-dependent, altitude-dependent and charge-dependent detection efficiency for a given instrument. In this paper, we investigate the aerodynamics for a typical electrostatic detector design. We first quantify the flow field of the background gas, then introduce particles in the flow field and determine their trajectories around the payload structure. We use two different models to trace particles in the flow field, a Continuous motion model and a Brownian motion model. Brownian motion is shown to be of basic importance for the smallest particles. Detection efficiencies are determined for three detector designs, including two with ventilation holes to allow airflow through the detector. Results from this investigation show that rocket-borne smoke detection with conventional detectors is largely limited to altitudes above 75 km. The flow through a ventilated detector has to be relatively large in order to significantly improve the detection efficiency.

  • 27.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Use of O2 airglow for calibrating direct atomic oxygen measurements from sounding rockets2009In: Atmospheric Measurement Techniques, ISSN 1867-1381, Vol. 2, p. 801-812Article in journal (Refereed)
    Abstract [en]

    Accurate knowledge about the distribution of atomic oxygen is crucial for many studies of the mesosphere and lower thermosphere. Direct measurements of atomic oxygen by the resonance fluorescence technique at 130 nm have been made from many sounding rocket payloads in the past. This measurement technique yields atomic oxygen profiles with good sensitivity and altitude resolution. However, accuracy is a problem as calibration and aerodynamics make the quantitative analysis challenging. Most often, accuracies better than a factor 2 are not to be expected from direct atomic oxygen measurements. As an example, we present results from the NLTE (Non Local Thermodynamic Equilibrium) sounding rocket campaign at Esrange, Sweden, in 1998, with simultaneous O2 airglow and O resonance fluorescence measurements. O number densities are found to be consistent with the nightglow analysis, but only within the uncertainty limits of the resonance fluorescence technique. Based on these results, we here describe how better atomic oxygen number densities can be obtained by calibrating direct techniques with complementary airglow photometer measurements and detailed aerodynamic analysis. Night-time direct O measurements can be complemented by photometric detection of the O2 (b1g+X3g-) Atmospheric Band at 762 nm, while during daytime the O2 (a1ΔgX3g-) Infrared Atmospheric Band at 1.27 μm can be used. The combination of a photometer and a rather simple resonance fluorescence probe can provide atomic oxygen profiles with both good accuracy and good height resolution.

  • 28.
    Hedin, Jonas
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Waldemarsson, Tomas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Giovane, Frank
    Naval Research Laboratory, Washington, DC.
    The aerodynamics of the MAGIC meteoric smoke sampler2007In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 40, no 6, p. 818-824Article in journal (Refereed)
    Abstract [en]

    The detection of nanometre-sized meteoric smoke particles in the Earth’s mesosphere and lower thermosphere is difficult. The particles are too small for optical detection and so far only the charged fraction of the particles has been probed by rocket-borne instruments. One way to obtain maximum information about the smoke particles is direct sampling with rocket-borne particle samplers. The MAGIC project (Mesospheric Aerosol – Genesis, Interaction and Composition) aims to quantitatively answer fundamental questions about the properties of smoke in the atmosphere. The first launch of such particle samplers was performed during the MAGIC rocket campaign from Esrange, Sweden, in January 2005. In order to characterise the sampling process, we have performed simulations of the trajectories of nanometre-sized dust particles towards the MAGIC detectors with a new particle motion model. An important feature of this model is the Brownian motion of the particles due to thermal collisions of the gas molecules. As a result, we obtain the detection efficiency for the MAGIC detectors as a function of altitude and particle size. Our simulations confirm that particles of radii down to 0.75 nm impact on the sampling surface with an efficiency exceeding 80% over the entire mesospheric altitude range of interest.

  • 29.
    Hendrickx, Koen
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Megner, Linda
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Siskind, D. E.
    Orsolini, Y. J.
    Nesse Tyssøy, H.
    Hervig, M.
    Observation of 27-day solar cycles in mesospheric production and descent of EPP-produced NO2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 10, p. 8978-8988Article in journal (Refereed)
    Abstract [en]

    Nitric oxide (NO) is produced by energetic particle precipitation (EPP) in the mesosphere-lower thermosphere (MLT) region, and during the polar winter, NO can descend to stratospheric altitudes where it destroys ozone. In this paper, we study the general scenario, as opposed to a case study, of NO production in the thermosphere due to energetic particles in the auroral region. We first investigate the relationship between NO production and two geomagnetic indices. The analysis indicates that the auroral electrojet index is a more suitable proxy for EPP-produced NO than the typically used midlatitude Ap index. In order to study the production and downward transport of NO from the lower thermosphere to the mesosphere, we perform superposed epoch analyses on NO observations made by the Solar Occultation For Ice Experiment instrument on board the Aeronomy of Ice in the Mesosphere satellite. The epoch analysis clearly shows the impact of the 27 day solar cycle on NO production. The effect is observed down to an altitude range of about 50 km to 65 km, depending on the hemisphere and the occurrence of stratospheric warmings. Initially, a rapid downward transport is noted during the first 10 days after EPP onset to an altitude of about 80–85 km, which is then followed by a slower downward transport of approximately 1–1.2 km/d to lower mesospheric altitudes in the order of 30 days.

  • 30.
    Hendrickx, Koen
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Megner, Linda
    Stockholm University, Faculty of Science, Department of Meteorology .
    Marsh, Daniel R.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Strandberg, Rickard
    Stockholm University, Faculty of Science, Department of Mathematics.
    Martinsson, Felix
    Stockholm University, Faculty of Science, Department of Mathematics.
    Relative Importance of Nitric Oxide Physical Drivers in the Lower Thermosphere2017In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 44, no 19, p. 10081-10087Article in journal (Refereed)
    Abstract [en]

    Nitric oxide (NO) observations from the Solar Occultation for Ice Experiment and Student Nitric Oxide Explorer satellite instruments are investigated to determine the relative importance of drivers of short-term NO variability. We study the variations of deseasonalized NO anomalies by removing a climatology, which explains between approximately 70% and 90% of the total NO budget, and relate them to variability in geomagnetic activity and solar radiation. Throughout the lower thermosphere geomagnetic activity is the dominant process at high latitudes, while in the equatorial region solar radiation is the primary source of short-term NO changes. Consistent results are obtained on estimated geomagnetic and radiation contributions of NO variations in the two data sets, which are nearly a decade apart in time. The analysis presented here can be applied to model simulations of NO to investigate the accuracy of the parametrized physical drivers.

  • 31.
    Hultgren, Kristoffer
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jorg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Tomographic and spectral views on the lifecycle of polar mesospheric clouds from Odin/OSIRIS2014In: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996, Vol. 119, no 24, p. 14129-14143Article in journal (Refereed)
    Abstract [en]

    Vertical and horizontal structures of Polar Mesospheric Clouds (PMC) have been recovered by tomographic retrieval from the OSIRIS instrument aboard the Odin satellite. The tomographic algorithm has been used to return local scattering coefficients at seven wavelengths in the ultraviolet. This spectral information is used to retrieve PMC particle sizes, number density, and ice mass density. While substantial horizontal variations are found, local vertical structures are overall consistent with the idea of a growth-sedimentation process leading to a visible cloud. Large numbers of small particles are present near the top of the observed cloud layer. Toward lower altitudes, particle sizes increase while particle number densities decrease. A close relationship is found between the distribution of local PMC scattering coefficient and ice mass density. The bottom of the cloud often features large particles with mode radii exceeding 70 nm that rain out of the cloud before sublimating. The number density of these large particles is small, and they do not contribute significantly to the overall cloud brightness. As a consequence, the presence of these large particles can be difficult to identify for remote sensing techniques that integrate over the entire cloud column. When it comes to deriving absolute values of particle mode radius and number density, there is a strong sensitivity to assumptions on the mathematical form of the particle size distribution. We see a continued strong need to resolve this issue by co-analysis of various remote sensing techniques and observation geometries.

  • 32.
    Hultgren, Kristoffer
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Tomographic and spectral views on the lifecycle of Polar Mesospheric Clouds from Odin/OSIRISIn: Journal of Geophysical Research - Atmospheres, ISSN 2169-897X, E-ISSN 2169-8996Article in journal (Refereed)
  • 33.
    Hultgren, Kristoffer
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Degenstein, Doug
    Bourassa, Adam
    Lloyd, Nick
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    First simultaneous retrievals of horizontal and vertical structures of Polar Mesospheric Clouds from Odin/OSIRIS tomography2013In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 104, p. 213-223Article in journal (Refereed)
    Abstract [en]

    Limb-scanning satellites can provide global information about the vertical structure of Polar Mesospheric Clouds. However, information about horizontal structures usually remains limited. In eighteen days during the northern hemisphere summers of 2010 and 2011, the Odin satellite was operated in a special mesospheric mode with short limb scans limited to the altitude range of Polar Mesospheric Clouds. For Odin's Optical Spectrograph and InfraRed Imager System (OSIRIS) this provides multiple views through a given cloud volume, which forms a basis for tomographic analyses of the vertical/horizontal cloud structures. Here we present an algorithm for a tomographic analysis of mesospheric clouds based on maximum probability techniques. We also present the first simultaneously retrieved vertical and horizontal Polar Mesospheric Cloud structures. The findings show that the tomographic algorithm is able to locate detailed structures such as tilts, stratifications, or holes that cannot be analyzed by other limb, nadir, or ground-based measurements. We find a mean peak altitude of the clouds to be 83.6 km. We identify horizontal patches down to sizes of 300 km, which corresponds to a horizontal resolution that is limited by the available number of limb scans.

  • 34.
    Hultgren, Kristoffer
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Kornich, Heiner
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gerding, Michael
    Hoffmann, Peter
    Lossow, Stefan
    Megner, Linda
    What caused the exceptional mid-latitudinal Noctilucent Cloud event in July 2009?2011In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 73, no 14-15, p. 2125-2131Article in journal (Refereed)
    Abstract [en]

    Noctilucent Clouds (NLCs) are rarely observed at mid-latitudes. In July 2009, strong NLCs were recorded from both Paris and Nebraska, located at latitudes 48 degrees N and 41 degrees N, respectively. The main focus of this work is on the atmospheric conditions that have led to NLCs at these latitudes. We investigate to what extent these clouds may be explained by local formation or by transport from higher latitudes. The dynamical situation is analyzed in terms of wind fields created from Aura/MLS temperature data and measured by radar. We discuss possible tidal effects on the transport and examine the general planetary wave activity during these days. The winds do not seem sufficient to transport NLC particles long southward distances. Hence a local formation is rather likely. In order to investigate the possibility of local NLC formation, the CARMA microphysical model has been applied with temperature data from MLS as input. The results from the large-scale datasets are compared to NLC observations by Odin and to local NLC, temperature and wind measurements by lidar and radar. The reason for the exceptional NLC formation is most likely a combination of local temperature variations by diurnal tides, advantageously located large-scale planetary waves, and general mesospheric temperature conditions that were 5-10 K colder than in previous years. The results also point to that NLCs are very unlikely to occur at latitudes below 50 degrees N during daytime. This conclusion can be made from a tidal temperature mode with cold temperatures during nighttime and temperatures above the limit for NLC occurrence during daytime. The best time for observing mid-latitude NLCs is during the early morning hours.

  • 35.
    Karlsson, Bodil
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology.
    Challenges in the limb retrieval of noctilucent cloud properties from Odin/OSIRIS2005In: Advances in Space Research, Vol. 36, p. 935-942Article in journal (Refereed)
  • 36. Knappmiller, S.
    et al.
    Rapp, M.
    Robertson, S.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Charging of meteoric smoke and ice particles in the mesosphere including photoemission and photodetachment rates2011In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 73, no 14-15, p. 2212-2220Article in journal (Refereed)
    Abstract [en]

    Charge probability distributions and charge number densities are presented for three types of particles that occur in the polar summer mesosphere: NLC particles (ice particles), meteoric smoke particles (MSP), and MSP covered in ice. Charge probability distributions and charge number densities are found using a kinetic rate equation including photoemission and photodetachment rates. Due to the large workfunction of ice, photoemission rates for NLC particles are negligible. The electron affinity for ice is an order of magnitude lower than the workfunction, thus photodetachment is a significant charging process. In the absence of photo-charging effects, an NLC particle will charge negatively by electron collection, and a particle above 10 nm in radius will have a charge that increases approximately linearly with radius. However when photodetachment is included, the number of electrons that attach to an NLC particle above 10 nm in radius is limited. Metal oxides such as Fe(2)O(3) have been suggested as a primary constituent of MSP. Assuming that the optical properties of MSP can be represented by these metal oxides, photoemission and photodetachment rates are comparable to electron attachment rates resulting in positively charged MSP. Photoemission, therefore, may help explain the multiple observations of positive particles observed in the mesosphere. In addition, the existence of positively charged MSP has implications for the formation of NLC particles. NLC particles with a core of meteoric smoke have an increased photodetachment rate, making the mean charge of the particle less negative. NLC particles with densities larger than the electron and ion densities calculated both with and without photodetachment show the coexistence of positive and negative particles. Large number densities of NLC particles are another possible explanation for the simultaneous occurrence of positive and negative particles observed by rocket-borne instruments.

  • 37.
    Lossow, Stefan
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Witt, Georg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Dalin, P.
    Swedish Institute of Space Physics.
    Kirkwood, S.
    Swedish Institute of Space Physics.
    Schmidlin, F.J.
    NASA Goddard Space Flight Center, Wallops Island, VA.
    Fricke, K. H.
    Physikalisches Institut der Universität Bonn.
    Blum, U.
    Physikalisches Institut der Universität Bonn.
    Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign2009In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 9, p. 4407-4417Article in journal (Refereed)
    Abstract [en]

    The Hygrosonde-2 campaign took place on 16 December 2001 at Esrange/Sweden (68° N, 21° E) with the aim to investigate the small scale distribution of water vapour in the middle atmosphere in the vicinity of the Arctic polar vortex. In situ balloon and rocket-borne measurements of water vapour were performed by means of OH fluorescence hygrometry. The combined measurements yielded a high resolution water vapour profile up to an altitude of 75 km. Using the characteristic of water vapour being a dynamical tracer it was possible to directly relate the water vapour data to the location of the polar vortex edge, which separates air masses of different character inside and outside the polar vortex. The measurements probed extra-vortex air in the altitude range between 45 km and 60 km and vortex air elsewhere. Transitions between vortex and extra-vortex usually coincided with wind shears caused by gravity waves which advect air masses with different water vapour volume mixing ratios. From the combination of the results from the Hygrosonde-2 campaign and the first flight of the optical hygrometer in 1994 (Hygrosonde-1) a clear picture of the characteristic water vapour distribution inside and outside the polar vortex can be drawn. Systematic differences in the water vapour concentration between the inside and outside of the polar vortex can be observed all the way up into the mesosphere. It is also evident that in situ measurements with high spatial resolution are needed to fully account for the small-scale exchange processes in the polar winter middle atmosphere.

  • 38.
    Lossow, Stefan
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Urban, J.
    Chalmers University of Technology, Department of Radio and Space Science.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Eriksson, P.
    Chalmers University of Technology, Department of Radio and Space Science.
    Murtagh, D.
    Chalmers University of Technology, Department of Radio and Space Science.
    Observations of the mesospheric semi-annual oscillation (MSAO) in water vapour by Odin/SMR2008In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 8, p. 6527-6540Article in journal (Refereed)
    Abstract [en]

    Mesospheric water vapour measurements taken by the SMR instrument aboard the Odin satellite between 2002 and 2006 have been analysed with focus on the mesospheric semi-annual circulation in the tropical and subtropical region. This analysis provides the first complete picture of mesospheric SAO in water vapour, covering altitudes above 80 km where previous studies were limited. Our analysis shows a clear semi-annual variation in the water vapour distribution in the entire altitude range between 65 km and 100 km in the equatorial area. Maxima occur near the equinoxes below 75 km and around the solstices above 80 km. The phase reversal occurs in the small layer in-between, consistent with the downward propagation of the mesospheric SAO in the zonal wind in this altitude range. The SAO amplitude exhibits a double peak structure in the equatorial region, with maxima at about 75 km and 81 km. The observed amplitudes show higher values than an earlier analysis based on UARS/HALOE data. The upper peak amplitude remains relatively constant with latitude. The lower peak amplitude decreases towards higher latitudes, but recovers in the Southern Hemisphere subtropics. On the other hand, the annual variation is much more prominent in the Northern Hemisphere subtropics. Furthermore, higher volume mixing ratios during summer and lower values during winter are observed in the Northern Hemisphere subtropics, as compared to the corresponding latitude range in the Southern Hemisphere.

  • 39.
    Lossow, Stefan
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Urban, J.
    Chalmers University of Technology. Department of Radio and Space Science.
    Schmidt, H.
    Max Planck Institute for Meteorology. Atmosphere in the Earth System.
    Marsh, D.R.
    National Center for Atmospheric Research. Atmospheric Chemistry Division.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Eriksson, P.
    Chalmers University of Technology. Department of Radio and Space Science.
    Murtagh, Donal
    Chalmers University of Technology. Department of Radio and Space Science.
    Wintertime water vapor in the polar upper mesosphere and lower thermosphere: First satellite observations by Odin submillimeter radiometer2009In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, p. D10304-Article in journal (Refereed)
    Abstract [en]

    In this paper we present Odin submillimeter radiometer (Odin/SMR) water vapor measurements in the upper mesosphere and lower thermosphere with focus on the polar latitudes in winter. Measurements since 2003 have been compiled to provide a first overview of the water vapor distribution in this altitude range. Our observations show a distinct seasonal increase of the water vapor concentration during winter at a given altitude above 90 km. Above 95 km the observations exhibit the annual water vapor maximum during wintertime. Model simulations from the Hamburg Model of the Neutral and Ionized Atmosphere (HAMMONIA) and the Whole Atmosphere Community Climate Model version 3 (WACCM3) show results that are very similar to the observations. We suggest that the observed increase in water vapor during winter is mainly caused by a combination of upwelling of moister air from lower altitudes and diffusion processes. Distinct interhemispheric differences in the winter water vapor distribution in the upper mesosphere and lower thermosphere can be observed, both in the observations and the model results. The seasonal water vapor increase in the polar regions is much more pronounced in the Southern Hemisphere winter where higher concentrations can be observed. This observation is most likely due to interhemispheric differences in the underlying dynamics and diffusion processes

  • 40.
    Lossow, Stefan
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Urban, Joachim
    Chalmers University of Technology, Department of Radio and Space Science.
    Eriksson, Patrick
    Chalmers University of Technology, Department of Radio and Space Science.
    Murtagh, Donal
    Chalmers University of Technology, Department of Radio and Space Science.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Critical parameters for the retrieval of mesospheric water vapour and tempera- ture from Odin/SMR limb measurements at 557 GHz2007In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 40, no 6, p. 835-845Article in journal (Refereed)
    Abstract [en]

    Limb measurements at 557 GHz by the Sub-millimetre and Millimetre Radiometer (SMR) onboard the Odin satellite provide water vapour and temperature information throughout the mesosphere. A sensitivity study for these retrievals has been performed, in order to identify the most critical parameters affecting the retrievals, with focus on the polar summer mesosphere conditions. Uncertainties in the instrument characterisation and the a priori value chosen for the pointing offset were found to have significant effects on the retrieved profiles. It is also shown that spectroscopic parameters play a role. An obvious improvement of the water and temperature retrieval can be obtained when we account for some of these critical parameters. However, some further improvement of the instrument behaviour characterisation is still needed

  • 41.
    Megner, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Charged meteoric particles as ice nuclei in the mesosphere. Part 2: A feasibility study2009In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 71, no 12, p. 1236-1244Article in journal (Refereed)
    Abstract [en]

    Recondensed meteoric material, so-called meteoric smoke, has long been considered the main candidate for condensation nuclei for mesospheric ice formation. Recently however, model studies have shown that meteoric smoke particles are transported away from the polar region, where ice phenomena such as noctilucent clouds occur, before they can grow large enough to serve as ice condensation nuclei. In the accompanying paper it is argued that charging of the meteoric smoke particles may solve this dilemma by significantly altering the efficiency of the particles as condensation nuclei. In the present paper, the feasibility of this idea is investigated more quantitatively, by analysing the time scales of processes such as charging, recombination, and particle growth. Despite large uncertainties, especially in the charging efficiency of the smallest smoke particles, we show that reasonable assumptions yield number densities of charged condensation nuclei that are consistent with what is expected for mesospheric ice phenomena.

  • 42.
    Megner, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Rapp, M.
    Leibniz Inst Atmospher Phys, Kuhlungsborn, Germany .
    Siskind, D.E.
    USN, Res Lab, EO Hulburt Ctr Space Res, Washington, DC 20375 USA .
    Reduced meteoric smoke abundance at the summer pole - implications for mesospheric ice particle nucleation2008In: Advances of Space Research, ISSN 0273-1177, Vol. 41, no 1, p. 41-49Article in journal (Refereed)
    Abstract [en]

    Noctilucent clouds (NLC) and polar mesospheric summer echoes (PMSE) are phenomena that occur in the summertime polar regions due to the presence of ice particles around the mesopause. That ice particles are able to form in a region with such low water vapour concentration as the mesopause is noteworthy. Even though the summer mesopause is the coldest region on Earth, temperatures are generally not low enough for homogeneous nucleation to occur, which necessitates the presence of pre-existing condensation nuclei. The nature of these nuclei has long puzzled the scientific community and many candidates have been suggested, such as particles of meteoric origin, ion clusters, sodium bi-carbonate, sulfate aerosols and soot particles. Out of these the so-called "smoke particles", i.e. particles re-condensed from ablated meteoritic material, have long been considered the most likely. Generally, it has been believed that these particles exist in numbers of the order of thousands per cubic centimetre at the mesopause. This belief is based on 1-dimensional. studies of meteoric material. A recent 2-dimensional model study, which includes the atmospheric circulation from summer to winter pole however, suggests much lower number densities at the summer mesopause. We here investigate the implications of low number densities for the formation of ice particles. We find that even though resulting ice particle distribution may produce typical NLC brightness, the number density of ice particles is not consistent with what is expected for NLC and PMSE. In particular, it is much lower than the ice particle concentration (>1000 cm(-3)) typically expected to explain the "electron bite-outs" that are frequently observed in the vicinity of PMSE's. We therefore re-examine the assumptions and parameters that determine the smoke distribution. We show that even though the number of condensation nuclei at the polar summer mesopause can be increased within the uncertainties, the results in most scenarios remain insufficient. We show that charged particles, perhaps in combination with significant deviations from the mean mesospheric state, may be necessary for condensation of ice particles in the polar summer mesosphere. Hence, we raise the question whether the conventional ideas of nucleation on meteoric smoke, which are used in current mesospheric ice models, are correct.

  • 43.
    Megner, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Mikhail
    Stockholm University, Faculty of Science, Department of Meteorology .
    Baumgarten, G.
    Leibniz-Institute of Atmospheric Physics.
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Strelnikov, B.
    Leibniz-Institute of Atmospheric Physics.
    Robertson, S.
    University of Colorado. Department of Physics .
    Large mesospheric ice particles at exceptionally high altitudes2009In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 27, p. 943-951Article in journal (Refereed)
    Abstract [en]

    We here report on the characteristics of exceptionally high Noctilucent clouds (NLC) that were detected with rocket photometers during the ECOMA/MASS campaign at Andøya, Norway 2007. The results from three separate flights are shown and discussed in connection to lidar measurements. Both the lidar measurements and the large difference between various rocket passages through the NLC show that the cloud layer was inhomogeneous on large scales. Two passages showed a particularly high, bright and vertically extended cloud, reaching to approximately 88 km. Long time series of lidar measurements show that NLC this high are very rare, only one NLC measurement out of thousand reaches above 87 km. The NLC is found to consist of three distinct layers. All three were bright enough to allow for particle size retrieval by phase function analysis, even though the lowest layer proved too horizontally inhomogeneous to obtain a trustworthy result. Large particles, corresponding to an effective radius of 50 nm, were observed both in the middle and top of the NLC. The present cloud does not comply with the conventional picture that NLC ice particles nucleate near the temperature minimum and grow to larger sizes as they sediment to lower altitudes. Strong up-welling, likely caused by gravity wave activity, is required to explain its characteristics.

  • 44.
    Megner, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Rapp, M.
    Gumbel, J.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Distribution of meteoric smoke - sensitivity to microphysical properties and atmospheric conditions2006In: Atmospheric chemistry and physics, ISSN 1680-7316, Vol. 6, no 12, p. 4415-4426Article in journal (Refereed)
    Abstract [en]

    Meteoroids entering the Earth's atmosphere experience strong deceleration and ablate, whereupon the resulting material is believed to re-condense to nanometre-size "smoke particles". These particles are thought to be of great importance for many middle atmosphere phenomena, such as noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. The properties and distribution of meteoric smoke depend on poorly known or highly variable factors such as the amount, composition and velocity of incoming meteoric material, the efficiency of coagulation, and the state and circulation of the atmosphere. This work uses a one-dimensional microphysical model to investigate the sensitivities of meteoric smoke properties to these poorly known or highly variable factors. The resulting uncertainty or variability of meteoric smoke quantities such as number density, mass density, and size distribution are determined. It is found that the two most important factors are the efficiency of the coagulation and background vertical wind. The seasonal variation of the vertical wind in the mesosphere implies strong global and temporal variations in the meteoric smoke distribution. This contrasts the simplistic picture of a homogeneous global meteoric smoke layer, which is currently assumed in many studies of middle atmospheric phenomena. In particular, our results suggest a very low number of nanometre-sized smoke particles at the summer mesopause where they are thought to serve as condensation nuclei for noctilucent clouds.

  • 45.
    Megner, Linda
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Siskind, D. E.
    Rapp, M.
    Gumbel, J.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Global and temporal distribution of meteoric smoke: a two-dimensional simulation study2008In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 113, no D3, p. D03202-Article in journal (Refereed)
    Abstract [en]

    Meteoric material entering Earth's atmosphere ablates in the mesosphere and is then expected to recondense into tiny so-called “smoke particles.” These particles are thought to be of great importance for middle atmosphere phenomena like noctilucent clouds, polar mesospheric summer echoes, metal layers, and heterogeneous chemistry. Commonly used one-dimensional (1-D) meteoric smoke profiles refer to average global conditions and yield of the order of a thousand nanometer sized particles per cubic centimeter at the mesopause, independent of latitude and time of year. Using the first two-dimensional model of both coagulation and transport of meteoric material we here show that such profiles are too simplistic, and that the distribution of smoke particles indeed is dependent on both latitude and season. The reason is that the atmospheric circulation, which cannot be properly handled by 1-D models, efficiently transports the particles to the winter hemisphere and down into the polar vortex. Using the assumptions commonly used in 1-D studies results in number densities of nanometer sized particles of around 4000 cm−3 at the winter pole, while very few particles remain at the Arctic summer mesopause. If smoke particles are the only nucleation kernel for ice in the mesosphere this would imply that there could only be of the order of 100 or less ice particles cm−3 at the Arctic summer mesopause. This is much less than the ice number densities expected for the formation of ice phenomena (noctilucent clouds and polar mesospheric summer echoes) that commonly occur in this region. However, we find that especially the uncertainty of the amount of material that is deposited in Earth's atmosphere imposes a large error bar on this number, which may allow for number densities up to 1000 cm−3 near the polar summer mesopause. This efficient transport of meteoric material to the winter hemisphere and down into the polar vortex results in higher concentrations of meteoric material in the Arctic winter stratosphere than previously thought. This is of potential importance for the formation of the so-called stratospheric condensation nuclei layer and for stratospheric nucleation processes.

  • 46. Plane, John M. C.
    et al.
    Saunders, Russell W.
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Stegman, Jacek
    Stockholm University, Faculty of Science, Department of Meteorology .
    Khaplanov, Misha
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Lynch, Kristina A.
    Bracikowski, Phillip J.
    Gelinas, Lynette J.
    Friedrich, Martin
    Blindheim, Sandra
    Gausa, Michael
    Williams, Bifford P.
    A combined rocket-borne and ground-based study of the sodium layer and charged dust in the upper mesosphere2014In: Journal of Atmospheric and Solar-Terrestrial Physics, ISSN 1364-6826, E-ISSN 1879-1824, Vol. 118, p. 151-160Article in journal (Refereed)
    Abstract [en]

    The Hotel Payload 2 rocket was launched on January 31st 2008 at 20.14 LT from the Andoya Rocket Range in northern Norway (69.31 degrees N, 16.01 degrees E). Measurements in the 75-105 km region of atomic O, negatively-charged dust, positive ions and electrons with a suite of instruments on the payload were complemented by lidar measurements of atomic Na and temperature from the nearby ALOMAR observatory. The payload passed within 2.58 km of the lidar at an altitude of 90 km. A series of coupled models is used to explore the observations, leading to two significant conclusions. First, the atomic Na layer and the vertical profiles of negatively-charged dust (assumed to be meteoric smoke particles), electrons and positive ions, can be modelled using a self-consistent meteoric input flux. Second, electronic structure calculations and Rice-Ramsperger-Kassel-Markus theory are used to show that even small Fe-Mg-silicates are able to attach electrons rapidly and form stable negatively-charged particles, compared with electron attachment to O-2 and O-3. This explains the substantial electron depletion between 80 and 90 km, where the presence of atomic O at concentrations in excess of 10(10) cm(-3) prevents the formation of stable negative ions.

  • 47.
    Rapp, M.
    et al.
    Leibniz Institute for Atmospheric Physics.
    Strelnikova, I.
    Leibniz Institute for Atmospheric Physics.
    Strelnikov, B.
    Leibniz Institute for Atmospheric Physics.
    Latteck, R.
    Leibniz Institute for Atmospheric Physics.
    Baumgarten, G.
    Leibniz Institute for Atmospheric Physics.
    Li, Q.
    Leibniz Institute for Atmospheric Physics.
    Megner, Linda
    Stockholm University, Faculty of Science, Department of Meteorology .
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Friedrich, M.
    Graz University of Technology. Institute of Communication Networks and Satellite Communications.
    Hoppe, U.-P.
    Norwegian Defence Research Establishment (FFI), .
    Robertson, S.
    University of Colorado. Department of Physics.
    First in situ measurement of the vertical distribution of ice volume in a mesospheric ice cloud during the ECOMA/MASS rocket-campaign2009In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, no 27, p. 755-766Article in journal (Refereed)
    Abstract [en]

    We present in situ observations of mesospheric ice particles with a new particle detector which combines a classical Faraday cup with the active photoionization of particles and subsequent detection of photoelectrons. Our observations of charged particles and free electrons within a decaying PMSE-layer reveal that the presence of charged particles is a necessary but not sufficient condition for the presence of PMSE. That is, additional requirements like a sufficiently large electron density – which we here estimate to be on the order of ~100 cm−3 – and the presence of small scale structures (commonly assumed to be caused by turbulence) need to be satisfied. Our photoelectron measurements reveal a very strong horizontal structuring of the investigated ice layer, i.e., a very broad layer (82–88 km) seen on the upleg is replaced by a narrow layer from 84.5–86 km only 50 km apart on the downleg of the rocket flight. Importantly, the qualitative structure of these photoelectron profiles is in remarkable qualitative agreement with photometer measurements on the same rocket thus demonstrating the reliability of this new technique. We then show that the photoelectron currents are a unique function of the ice particle volume density (and hence ice mass) within an uncertainty of only 15% and we derive corresponding altitude profiles of ice volume densities. Derived values are in the range ~2–8×10−14 cm3/cm3 (corresponding to mass densities of ~20–80 ng/m3, and water vapor mixing ratios of 3–12 ppm) and are the first such estimates with the unique spatial resolution of an in situ measurement.

  • 48.
    Rapp, Markus
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Hedin, Jonas
    Stockholm University, Faculty of Science, Department of Meteorology .
    Strelnikova, Irina
    Friedrich, Martin
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Lübken, Franz-Josef
    Observations of positively charged nanoparticles in the nighttime polar mesosphere2005In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 32, p. L23821-Article in journal (Refereed)
    Abstract [en]

    We present results of in situ measurements of charged nanoparticles, electrons, and positive ions obtained during a sounding rocket flight in October 2004 from Kiruna, Sweden, under nighttime conditions. The particle measurement reveals positive charge signatures in the altitude range between 80 and 90 km corresponding to peak charge number densities of ∼100 e/cm3 at around 86 km. Aerodynamical analysis of the sampling efficiency of our instrument reveals that the particles must have been larger than 2 nm assuming spherical particles with a density of 3 g/cm3. The plasma environment of the observed particles is dominated by negative and positive ions, with only few free electrons. A calculation of the mean particle charge expected for particles in a plasma consisting of electrons and positive and negative ions shows that the presence of sufficiently heavy and numerous negative ions (i.e., m n > 300 amu and λ ≥ 50) can explain the observed positive particle charge.

  • 49. Rapp, Markus
    et al.
    Strelnikova, Irina
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology.
    Meteoric smoke particles: Evidence from rocket and radar techniques2007In: Advances in Space Research, ISSN 0273-1177, Vol. 40, no 6, p. 809-817Article in journal (Refereed)
  • 50. Rapp, Markus
    et al.
    Strelnikova, Irina
    Strelnikov, Boris
    Hoffmann, Peter
    Friedrich, Martin
    Gumbel, Jörg
    Stockholm University, Faculty of Science, Department of Meteorology .
    Megner, Linda
    Stockholm University, Faculty of Science, Department of Meteorology .
    Hoppe, Ulf -Peter
    Robertson, Scott
    Knappmiller, Scott
    Wolff, Mareile
    Marsh, Daniel R.
    Rocket-borne in situ measurements of meteor smoke: Charging properties and implications for seasonal variation2010In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 115, p. D00I16-Article in journal (Refereed)
    Abstract [en]

    Rocket-borne observations of meteoric smoke particles (MSPs) are presented from three campaigns at polar latitudes (69 degrees N) in September 2006, and in the summers of 2007 and 2008. MSPs are detected using a novel technique based on photoelectron emission from the particles after stimulation by UV photons emitted by a xenon flashlamp. Resulting photoelectron currents are shown to be proportional to particle volume density. September results match model predictions qualitatively at altitudes from 65 to 85 km while measurements at higher altitudes are contaminated by photoelectrons from NO and O-2((1)Delta(g)). Contamination below this altitude can be excluded based on concurrent satellite observations. The observations show a large variability from flight to flight. Part of this variability can be attributed to differences in the charging of MSPs during day and night. Finally we find that MSP volume density in summer can exceed that during September. Analyzing model simulations of the global transport and microphysics of these particles, we show that our observations are in agreement with the model predictions, even though number densities of particles with radii >1 nm, which have long been thought to be suitable condensation nuclei for mesospheric ice particles, show the opposite behavior. It is shown that this discrepancy is caused by the fact that even larger particles (similar to 3 nm) dominate the volume density and that transport affects these different particle sizes in different ways. These results reinforce previous model findings according to which seasonal MSP variability is mainly driven by the global circulation and corresponding transport.

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