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  • 1.
    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 1867-8548, Vol. 6, no 1, 91-98 p.Article 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.

  • 2.
    Engström, J. E.
    et al.
    Stockholm University, Faculty of Science, Department of Meteorology .
    Leck, Caroline
    Stockholm University, Faculty of Science, Department of Meteorology .
    Reducing uncertainties associated with filter-based optical measurements of light absorbing carbon particles with chemical information2011In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 4, no 8, 1553-1566 p.Article in journal (Refereed)
    Abstract [en]

    The presented filter-based optical method for determination of soot (light absorbing carbon or Black Carbon, BC) can be implemented in the field under primitive conditions and at low cost. This enables researchers with small economical means to perform monitoring at remote locations, especially in the Asia where it is much needed. One concern when applying filter-based optical measurements of BC is that they suffer from systematic errors due to the light scattering of non-absorbing particles co-deposited on the filter, such as inorganic salts and mineral dust. In addition to an optical correction of the non-absorbing material this study provides a protocol for correction of light scattering based on the chemical quantification of the material, which is a novelty. A newly designed photometer was implemented to measure light transmission on particle accumulating filters, which includes an additional sensor recording backscattered light. The choice of polycarbonate membrane filters avoided high chemical blank values and reduced errors associated with length of the light path through the filter. Two protocols for corrections were applied to aerosol samples collected at the Maldives Climate Observatory Hanimaadhoo during episodes with either continentally influenced air from the Indian/Arabian subcontinents (winter season) or pristine air from the Southern Indian Ocean (summer monsoon). The two ways of correction (optical and chemical) lowered the particle light absorption of BC by 63 to 61 %, respectively, for data from the Arabian Sea sourced group, resulting in median BC absorption coefficients of 4.2 and 3.5 Mm(-1). Corresponding values for the South Indian Ocean data were 69 and 97% (0.38 and 0.02 Mm(-1)). A comparison with other studies in the area indicated an overestimation of their BC levels, by up to two orders of magnitude. This raises the necessity for chemical correction protocols on optical filter-based determinations of BC, before even the sign on the radiative forcing based on their effects can be assessed.

  • 3. Karnezi, E.
    et al.
    Riipinen, Ilona
    Stockholm University, Faculty of Science, Department of Applied Environmental Science (ITM).
    Pandis, S. N.
    Measuring the atmospheric organic aerosol volatility distribution: a theoretical analysis2014In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 7, no 9, 2953-2965 p.Article in journal (Refereed)
    Abstract [en]

    Organic compounds represent a significant fraction of submicrometer atmospheric aerosol mass. Even if most of these compounds are semi-volatile in atmospheric concentrations, the ambient organic aerosol volatility is quite uncertain. The most common volatility measurement method relies on the use of a thermodenuder (TD). The aerosol passes through a heated tube where its more volatile components evaporate, leaving the less volatile components behind in the particulate phase. The typical result of a thermodenuder measurement is the mass fraction remaining (MFR), which depends, among other factors, on the organic aerosol (OA) vaporization enthalpy and the accommodation coefficient. We use a new method combining forward modeling, introduction of experimental error, and inverse modeling with error minimization for the interpretation of TD measurements. The OA volatility distribution, its effective vaporization enthalpy, the mass accommodation coefficient and the corresponding uncertainty ranges are calculated. Our results indicate that existing TD-based approaches quite often cannot estimate reliably the OA volatility distribution, leading to large uncertainties, since there are many different combinations of the three properties that can lead to similar thermograms. We propose an improved experimental approach combining TD and isothermal dilution measurements. We evaluate this experimental approach using the same model, and show that it is suitable for studies of OA volatility in the lab and the field.

  • 4. Reid, Will
    et al.
    Achtert, Peggy
    Stockholm University, Faculty of Science, Department of Meteorology .
    Ivchenko, Nickolay
    Magnusson, Patrick
    Kuremyr, Tobias
    Shepenkov, Valeriy
    Tibert, Gunnar
    Technical Note: A novel rocket-based in situ collection technique for mesospheric and stratospheric aerosol particles2013In: Atmospheric Measurement Techniques, ISSN 1867-8548, Vol. 6, no 3, 777-785 p.Article in journal (Refereed)
    Abstract [en]

    A technique for collecting aerosol particles between altitudes of 17 and 85 km is described. Spin-stabilized collection probes are ejected from a sounding rocket allowing for multi-point measurements. Each probe is equipped with 110 collection samples that are 3 mm in diameter. The collection samples are one of three types: standard transmission electron microscopy carbon grids, glass fibre filter paper or silicone gel. Collection samples are exposed over a 50 m to 5 km height range with a total of 45 separate ranges. Post-flight electron microscopy will give size-resolved information on particle number, shape and elemental composition. Each collection probe is equipped with a suite of sensors to capture the probe's status during the fall. Parachute recovery systems along with GPS-based localization will ensure that each probe can be located and recovered for post-flight analysis.

  • 5. Renard, Jean-Baptiste
    et al.
    Dulac, Francois
    Berthet, Gwenael
    Lurton, Thibaut
    Vignelles, Damien
    Jegou, Fabrice
    Tonnelier, Thierry
    Jeannot, Matthieu
    Coute, Benoit
    Akiki, Rony
    Verdier, Nicolas
    Mallet, Marc
    Gensdarmes, Francois
    Charpentier, Patrick
    Mesmin, Samuel
    Duverger, Vincent
    Dupont, Jean-Charles
    Elias, Thierry
    Crenn, Vincent
    Sciare, Jean
    Zieger, Paul
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Salter, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Roberts, Tjarda
    Giacomoni, Jerome
    Gobbi, Matthieu
    Hamonou, Eric
    Olafsson, Haraldur
    Dagsson-Waldhauserova, Pavla
    Camy-Peyret, Claude
    Mazel, Christophe
    Decamps, Thierry
    Piringer, Martin
    Surcin, Jeremy
    Daugeron, Daniel
    LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles - Part 12016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 4, 1721-1742 p.Article in journal (Refereed)
    Abstract [en]

    The study of aerosols in the troposphere and in the stratosphere is of major importance both for climate and air quality studies. Among the numerous instruments available, optical aerosol particles counters (OPCs) provide the size distribution in diameter range from about 100 nm to a few tens of mu m. Most of them are very sensitive to the nature of aerosols, and this can result in significant biases in the retrieved size distribution. We describe here a new versatile optical particle/sizer counter named LOAC (Light Optical Aerosol Counter), which is light and compact enough to perform measurements not only at the surface but under all kinds of balloons in the troposphere and in the stratosphere. LOAC is an original OPC performing observations at two scattering angles. The first one is around 12 degrees, and is almost insensitive to the refractive index of the particles; the second one is around 60 degrees and is strongly sensitive to the refractive index of the particles. By combining measurement at the two angles, it is possible to retrieve the size distribution between 0.2 and 100 mu m and to estimate the nature of the dominant particles (droplets, carbonaceous, salts and mineral particles) when the aerosol is relatively homogeneous. This typology is based on calibration charts obtained in the laboratory. The uncertainty for total concentrations measurements is +/- 20% when concentrations are higher than 1 particle cm 3 (for a 10 min integration time). For lower concentrations, the uncertainty is up to about +/- 60% for concentrations smaller than 10 2 particle cm(-3). Also, the uncertainties in size calibration are +/- 0.025 mu m for particles smaller than 0.6 mu m, 5% for particles in the 0.7-2 mu m range, and 10% for particles greater than 2 mu m. The measurement accuracy of sub-micronic particles could be reduced in a strongly turbid case when concentration of particles > 3 mu m exceeds a few particles cm(-3). Several campaigns of cross-comparison of LOAC with other particle counting instruments and remote sensing photometers have been conducted to validate both the size distribution derived by LOAC and the retrieved particle number density. The typology of the aerosols has been validated in well-defined conditions including urban pollution, desert dust episodes, sea spray, fog, and cloud. Comparison with reference aerosol mass monitoring instruments also shows that the LOAC measurements can be successfully converted to mass concentrations.

  • 6. Renard, Jean-Baptiste
    et al.
    Dulac, Francois
    Berthet, Gwenael
    Lurton, Thibaut
    Vignelles, Damien
    Jegou, Fabrice
    Tonnelier, Thierry
    Jeannot, Matthieu
    Coute, Benoit
    Akiki, Rony
    Verdier, Nicolas
    Mallet, Marc
    Gensdarmes, Francois
    Charpentier, Patrick
    Mesmin, Samuel
    Duverger, Vincent
    Dupont, Jean-Charles
    Elias, Thierry
    Crenn, Vincent
    Sciare, Jean
    Zieger, Paul
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Salter, Matthew
    Stockholm University, Faculty of Science, Department of Environmental Science and Analytical Chemistry.
    Roberts, Tjarda
    Giacomoni, Jerome
    Gobbi, Matthieu
    Hamonou, Eric
    Olafsson, Haraldur
    Dagsson-Waldhauserova, Pavla
    Camy-Peyret, Claude
    Mazel, Christophe
    Decamps, Thierry
    Piringer, Martin
    Surcin, Jeremy
    Daugeron, Daniel
    LOAC: a small aerosol optical counter/sizer for ground-based and balloon measurements of the size distribution and nature of atmospheric particles - Part 22016In: Atmospheric Measurement Techniques, ISSN 1867-1381, E-ISSN 1867-8548, Vol. 9, no 8, 3673-3686 p.Article in journal (Refereed)
    Abstract [en]

    In the companion (Part I) paper, we have described and evaluated a new versatile optical particle counter/sizer named LOAC (Light Optical Aerosol Counter), based on scattering measurements at angles of 12 and 60A degrees. That allows for some typology identification of particles (droplets, carbonaceous, salts, and mineral dust) in addition to size-segregated counting in a large diameter range from 0.2aEuro-A mu m up to possibly more than 100aEuro-A mu m depending on sampling conditions (Renard et al., 2016). Its capabilities overpass those of preceding optical particle counters (OPCs) allowing the characterization of all kind of aerosols from submicronic-sized absorbing carbonaceous particles in polluted air to very coarse particles (> 10-20aEuro-A mu m in diameter) in desert dust plumes or fog and clouds. LOAC's light and compact design allows measurements under all kinds of balloons, on-board unmanned aerial vehicles (UAVs) and at ground level. We illustrate here the first LOAC airborne results obtained from a UAV and a variety of scientific balloons. The UAV was deployed in a peri-urban environment near Bordeaux in France. Balloon operations include (i) tethered balloons deployed in urban environments in Vienna (Austria) and Paris (France), (ii) pressurized balloons drifting in the lower troposphere over the western Mediterranean (during the Chemistry-Aerosol Mediterranean Experiment - ChArMEx campaigns), (iii) meteorological sounding balloons launched in the western Mediterranean region (ChArMEx) and from Aire-sur-l'Adour in south-western France (VOLTAIRE-LOAC campaign). More focus is put on measurements performed in the Mediterranean during (ChArMEx) and especially during African dust transport events to illustrate the original capability of balloon-borne LOAC to monitor in situ coarse mineral dust particles. In particular, LOAC has detected unexpected large particles in desert sand plumes.

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