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Communication incl. Poster: BibTeX citation key:  Nureta
Nuret, M., Bock, O., Lafore, J.-P., Guichard, F., Parker, D. J., Fink, A. H. & Houngninou, E. 2009. Correction of humidity bias for Vaisala RS80-A and MODEM sondes during AMMA 2006 observing period. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: Devic 2009-09-03 16:37:16    Last Edited by: roussot 2009-10-18 18:52:16
Categories: Weather to Climatic modelling and forecasting
Keywords: Precipitation, SOP
Creators: Bock, Fink, Guichard, Houngninou, Lafore, Nuret, Parker
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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During the African Monsoon Multidisciplinary Analyses (AMMA) program whose Special Observing Period took place over West Africa in 2006, a major effort has been devoted to monitor the atmosphere and its water cycle. The radiosoundings network has been upgraded and enhanced, and GPS receivers deployed. Three types of sondes have been used ( RS80-A and RS92 from Vaisala and M2K2 from MODEM). The launch rate raised up to 8 launches/day during Intensive Obervations Periods (IOPs) at Abuja (RS92), Niamey (RS80-A and RS92), Tamale (RS92), Parakou (M2K2) and Cotonou (M2K2).
The various sondes used in the campaign exhibit a significant humidity bias: i) large dry bias for RS80-A at daytime and nighttime, ii) dry bias for RS92 and M2K2 at daytime, iii) and moist bias for M2K2 and RS92 at night-time.
This presentation makes use of a simple but robust statistical approach to correct the bias. Validation against independent GPS data shows that a first correction, implemented in the database in January 2009, removes the large (up to -15%) dry night bias of the Vaisala RS-80A, and strongly reduces the large dry bias (up to -20%) encountered for daytime launches. A second correction (available on request) removes the moderate (+5%) moist bias of the MODEM M2K2 sondes diagnosed for night launches. The corrections dramatically modify the CAPE, which become much more in line with expected values over the region. A final correction (under development) will address the remaining daytime bias that affects all sondes, thanks to an inter-comparison exercise performed in Niamey in September 2008 using a reference sonde (SnowWhite from MeteoLabor).
Last Edited by: roussot