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Communication incl. Poster: BibTeX citation key:  Bock
Bock, O., Meynadier, R., Guichard, F., Boone, A. & Gounou, A. 2009. Diurnal cycle of the West African Monsoon water cycle: Regional and seasonal variability. Work presented at Third International AMMA Conference, July 20—24, at Ouagadougou, Burkina Faso.
Added by: roussot 2009-10-19 20:40:04
Categories: Water cycle
Keywords: Diurnal cycle
Creators: Bock, Boone, Gounou, Guichard, Meynadier
Publisher: African Monsoon Multidisciplinary Analyses (Ouagadougou, Burkina Faso)
Collection: Third International AMMA Conference

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The ground-based Global Positioning System (GPS) receivers deployed in the framework of AMMA provide an unprecedented insight into diurnal variations of precipitable water vapour (PWV) over West Africa. They display a strong seasonal dynamics and distinct features along latitude. Overall, GPS data point to the significance of an afternoon maximum of PWV during the monsoon season everywhere except at Niamey and Ouagadougou during the transition period in April-May. The diurnal anomaly reaches ± 1-1.5 mm of PWV. In terms of tendency, the diurnal maximum reaches ± 0.5 mm h-1, which is almost as large as the precipitation rate and evapo-transpiration rate over the region (Soudan and Sahel). The GPS PWV tendencies are used together with surface evapo-transpiration estimates from the ISBA land surface model and TRMM 3B42v6 precipitation data to estimate three-hourly column integrated moisture budgets. Moisture flux convergence is hence estimated as a residual of the water budget equation. The diurnal cycle of the different water budget terms are discussed on the basis of monthly averages (seasonal cycle) as a function of location. In order to get insight into the underlying atmospheric processes, high-resolution radiosonde data and the ECMWF model analysis and forecasts are used also. The confrontation of water budget terms from the model and observations provides also a diagnostic for the assessment of the model physics and assimilation scheme.
Added by: roussot