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Tropopause and hygropause variability over the equatorial Indian Ocean during February and March 1999

McKenzie, Robert and Schiller, Cornelius and Peter, Tomas and Adriani, Alberto and Beuermann, Jürgen and Cairo, Francesco and Corti, Tino and DiDonfrancesco, G. and Gensch, I. and Kiemle, C. and Krämer, M. and Kröger, C. and Merkulov, S. and Oulanovsky, A. and Ravegnani, F. and Rohs, S. and Rudakov, V. and Salter, P. and Santacesaria, V. and Stefanutti, L. and Yushkov, V. (2006) Tropopause and hygropause variability over the equatorial Indian Ocean during February and March 1999. Journal of Geophysical Research, 111, D18112. DOI: 10.1029/2005JD006639.

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Measurements of temperature, water vapor, total water, ozone, and cloud properties were made above the western equatorial Indian Ocean in February and March 1999. The cold-point tropopause was at a mean pressure-altitude of 17 km, equivalent to a potential temperature of 380 K, and had a mean temperature of 190 K. Total water mixing ratios at the hygropause varied between 1.4 and 4.1 ppmv. The mean saturation water vapor mixing ratio at the cold point was 3.0 ppmv. This does not accurately represent the mean of the measured total water mixing ratios because the air was unsaturated at the cold point for about 40% of the measurements. As well as unsaturation at the cold point, saturation was observed above the cold point on almost 30% of the profiles. In such profiles the air was saturated with respect to water ice but was free of clouds (i.e., backscatter ratio lower than 2) at potential temperatures more than 5 K above the tropopause and hygropause. Individual profiles show a great deal of variability in the potential temperatures of the cold point and hygropause. We attribute this to short timescale and space-scale perturbations superimposed on the seasonal cycle. There is neither a clear and consistent ‘‘setting’’ of the tropopause and hygropause to the same altitude by dehydration processes nor a clear and consistent separation of tropopause and hygropause by the Brewer-Dobson circulation. Similarly, neither the tropopause nor the hygropause provides a location where conditions consistently approach those implied by a simple ‘‘tropopause freeze drying’’ or ‘‘stratospheric fountain’’ hypothesis.

Document Type:Article
Title:Tropopause and hygropause variability over the equatorial Indian Ocean during February and March 1999
AuthorsInstitution or Email of Authors
McKenzie, RobertLancaster Univ., Lancaster, UK
Schiller, CorneliusFZ Jülich, Jülich
Peter, TomasETH Zürich, Zürich, CH
Adriani, AlbertoCNR Roma, Rom, I
Beuermann, JürgenFZ Jülich, Jülich
Cairo, FrancescoCNR Roma, Rom, I
Corti, TinoETH Zürich, Zürich, CH
DiDonfrancesco, G.ENEA, Rom, I
Gensch, I.FZ Jülich, Jülich
Krämer, M.FZ Jülich, Jülich
Kröger, C.Lancaster Univ., Lancaster, UK
Merkulov, S.Central Aerological Observ., Dolgoprudny, R
Oulanovsky, A.Central Aerological Observ., Dolgoprudny, R
Ravegnani, F.CNR, Bologna, I
Rohs, S.FZ Jülich, Jülich
Rudakov, V.Central Aerological Observ., Dolgoprudny, R
Salter, P.Met Office, Exeter, UK
Santacesaria, V.APE, Florence, I
Stefanutti, L.APE, Florence, I
Yushkov, V.Central Aerological Observ., Dolgoprudny, R
Journal or Publication Title:Journal of Geophysical Research
Refereed publication:Yes
In Open Access:No
In ISI Web of Science:Yes
Page Range:D18112
Keywords:tropical tropopause, airborne lidar, hygropause
HGF - Research field:Aeronautics, Space and Transport (old)
HGF - Program:Space (old)
HGF - Program Themes:W EO - Erdbeobachtung
DLR - Research area:Space
DLR - Program:W EO - Erdbeobachtung
DLR - Research theme (Project):W - Vorhaben LIDAR-Forschung und -Entwicklung (old)
Location: Oberpfaffenhofen
Institutes and Institutions:Institute of Atmospheric Physics > Lidar
Deposited By: Dr.rer.nat. Christoph Kiemle
Deposited On:29 Nov 2006
Last Modified:11 Nov 2014 21:56

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