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Observations of water vapour in the middle atmosphere
Stockholm University, Faculty of Science, Department of Meteorology.
Responsible organisation
2008 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Water vapour is the most important greenhouse gas and plays a fundamental role in the climate system and for the chemistry of the Earth's atmosphere. This thesis presents observations of water vapour in the middle atmosphere with a particular focus on the mesosphere. The majority of these observations presented in this thesis have been performed by the Swedish satellite Odin, providing global observations since 2001. Further observations come from the Hygrosonde-2 campaign in December 2001 based on balloon and rocket-borne measurements. A general overview of Odin's water vapour measurements in the middle atmosphere is given. The optimisation of the mesospheric water vapour retrieval is presented in detail.

The analysis of the observations has focused mainly on different dynamical aspects utilising the characteristic of water vapour as a dynamical tracer in the middle atmosphere. One application is the mesospheric part of the semi-annual oscillation (SAO). The observations reveal that this oscillation is the dominant pattern of variability between 30°S and 10°N in the mesosphere up to an altitude of 80 km. Above 90 km the SAO is dominating at all latitudes in the tropics and subtropics. It is shown that the SAO exhibits a distinct phase change between 75 km and 80 km in the tropical region.

This thesis also presents the first satellite observations of water vapour in the altitude range between 90 km and 110 km, extending the observational database up into the lower thermosphere. In the polar regions water vapour exhibits the annual maximum during winter time above 95 km, mainly caused by upwelling during this season. This behaviour is different from that observed in the subjacent part of the mesosphere where the annual maximum occurs during summer time.

The Hygrosonde-2 campaign provided a high resolution measurement of water vapour in the vicinity of the polar vortex edge. This edge prevents horizontal transport causing different water vapour characteristics inside and outside the polar vortex. The observations show that this separating behaviour extends high up into the mesosphere. Small scale transitions in the Hygrosonde-2 profile between conditions inside and outside the vortex coincided with wind shears caused by gravity waves.

Place, publisher, year, edition, pages
Stockholm: Meteorologiska institutionen (MISU) , 2008. , 63 p.
Keyword [en]
water vapour, mesosphere, stratosphere, dynamics, Odin satellite, limb sounding, microwave, tropics, polar winter
National Category
Meteorology and Atmospheric Sciences
Research subject
Meteorology
Identifiers
URN: urn:nbn:se:su:diva-8167ISBN: 978–91–7155–721–6 OAI: oai:DiVA.org:su-8167DiVA: diva2:199732
Public defence
2008-09-19, William-Olssonsalen, Geovetenskapens hus, Svante Arrhenius väg 8 A, Stockholm, 13:00
Opponent
Supervisors
Available from: 2008-09-10 Created: 2008-09-10Bibliographically approved
List of papers
1. Global observations of middle atmospheric water vapour by the Odin satellite: An overview
Open this publication in new window or tab >>Global observations of middle atmospheric water vapour by the Odin satellite: An overview
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2007 (English)In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 55, no 9, 1093-1102 p.Article in journal (Refereed) Published
Keyword
Odin, Sub-Millimetre Radiometer, Microwave limb sounding, Middle atmosphere, Water vapour, Water vapour isotopes
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-25442 (URN)10.1016/j.pss.2006.11.021 (DOI)000248018800010 ()
Note
Part of urn:nbn:se:su:diva-8167Available from: 2008-09-10 Created: 2008-09-10 Last updated: 2017-12-13Bibliographically approved
2. Critical parameters for the retrieval of mesospheric water vapour and tempera- ture from Odin/SMR limb measurements at 557 GHz
Open this publication in new window or tab >>Critical parameters for the retrieval of mesospheric water vapour and tempera- ture from Odin/SMR limb measurements at 557 GHz
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2007 (English)In: Advances in Space Research, ISSN 0273-1177, E-ISSN 1879-1948, Vol. 40, no 6, 835-845 p.Article in journal (Refereed) Published
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

Keyword
Limb sounding, Water vapour, Non-linear retrieval, Temperature, Polar summer mesosphere
National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-25443 (URN)10.1016/j.asr.2007.05.026 (DOI)000253589700014 ()
Note
Part of urn:nbn:se:su:diva-8167Available from: 2008-09-10 Created: 2008-09-10 Last updated: 2017-12-13Bibliographically approved
3. Observations of the mesospheric semi-annual oscillation (MSAO) in water vapour by Odin/SMR
Open this publication in new window or tab >>Observations of the mesospheric semi-annual oscillation (MSAO) in water vapour by Odin/SMR
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2008 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 8, 6527-6540 p.Article in journal (Refereed) Published
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.

National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-25444 (URN)000260927800015 ()
Note
Part of urn:nbn:se:su:diva-8167Available from: 2008-09-10 Created: 2008-09-10 Last updated: 2017-12-13Bibliographically approved
4. Wintertime water vapor in the polar upper mesosphere and lower thermosphere: First satellite observations by Odin submillimeter radiometer
Open this publication in new window or tab >>Wintertime water vapor in the polar upper mesosphere and lower thermosphere: First satellite observations by Odin submillimeter radiometer
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2009 (English)In: Journal of Geophysical Research, ISSN 0148-0227, E-ISSN 2156-2202, Vol. 114, D10304- p.Article in journal (Refereed) Published
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

National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-25445 (URN)10.1029/2008JD011462 (DOI)000266363900004 ()
Note
Part of urn:nbn:se:su:diva-8167Available from: 2008-09-10 Created: 2008-09-10 Last updated: 2017-12-13Bibliographically approved
5. Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign
Open this publication in new window or tab >>Middle atmospheric water vapour and dynamics in the vicinity of the polar vortex during the Hygrosonde-2 campaign
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2009 (English)In: Atmospheric Chemistry And Physics, ISSN 1680-7316, E-ISSN 1680-7324, Vol. 9, 4407-4417 p.Article in journal (Refereed) Published
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.

National Category
Meteorology and Atmospheric Sciences
Research subject
Atmospheric Sciences
Identifiers
urn:nbn:se:su:diva-25446 (URN)000267984400014 ()
Note
Part of urn:nbn:se:su:diva-8167Available from: 2008-09-10 Created: 2008-09-10 Last updated: 2017-12-13Bibliographically approved

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