Water Vapor Measurements in the UTLS at 936 nm by Stellar Occultations with GOMOS/ENVISAT

Abstract : The evolution of water vapor in the lower stratosphere is still a case for controversy, though its exact trend in response to climate change is important. Solomon et al. (2010) have argued that the observed decrease of about 10% after the year 2000 "acted to slow the rate of increase in global surface temperature... by about 25%... compared to that which would have occurred due to only CO2...". The GOMOS instrument on board ENVISAT (launched 2002 in a helio-synchronous polar orbit) contains a high resolution spectrometer for the measurement of O2 at 760 nm and H2O at 936 nm, with a resolution of ~0.05 nm per pixel. GOMOS is the first instrument measuring these species by the technique of stellar occultation, which is protected in principle from long term drift, an essential feature for long term monitoring of a possible trend. Nine stars are sufficiently bright to provide useful measurements for stratospheric H2O. However, the data retrieval has been plagued up to now by a severe pixel-to-pixel non-uniformity of the CCD detector giving a wet bias around 30 km, which is now corrected in the new reprocessing. Results of this reprocessing will be presented for the first time, in the altitude range 10-50 km with a vertical resolution 3-4 km. A comparison with LIDAR measurements at Mauna Kea allowed the validation of the new processing. Temporal variations at a constant latitude will be emphasized, consistent with the motion of the Intertropical Convergence Zone (ITCZ).A trend analysis will be also presented.
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Submitted on : Thursday, September 20, 2012 - 11:38:25 PM
Last modification on : Tuesday, May 14, 2019 - 11:01:44 AM

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  • HAL Id : hal-00734178, version 1

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Jean-Loup Bertaux, Alain Hauchecorne, Francis Dalaudier, Laurent Blanot. Water Vapor Measurements in the UTLS at 936 nm by Stellar Occultations with GOMOS/ENVISAT. ESA Conference on Advances in Atmospheric Science and Applications (ATMOS 2012), Jun 2012, Bruges, Belgium. ⟨hal-00734178⟩

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