Atmospheric water vapor transport and recycling in Equatorial Central Africa through NCEP/NCAR reanalysis data
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The characteristics of the main components of the water cycle over Equatorial Central Africa (ECA) were analysed using the 32-year period, spanning from 1968 to 2000, of the National Centers for Environmental Prediction-National Censearch (NCEP-) reanalysis project database. A special emphasis was given to identifying the causes of annual and interannual variability of water vapor flux and precipitation recycling. The results suggest that the first maximum of moisture convergence, during the rainy season MAM, comes from upper level moisture flux, related to the north component of the African Easterly Jet (AEJ-N). The second, and greatest, maximum in SON is found to be a consequence of low level moisture advection from the Atlantic Ocean. AEJ-N also drive the seasonal spatial pattern of moisture flux. The interannual variability of moisture flux is contributed mainly by the low level moisture advected from the Atlantic Ocean, underlying its crucial role for the regional climate. Studying the recycling ratio in ECA as a whole shows a low annual cycle whereas subregional scale analysis reveals high amplitude of the seasonal variation. Seasonal variability of the spatial gradient of precipitation recycling is regulated by both moisture flux direction and strength. The annual cycles of recycling ratio in the North and the South of ECA are regulated by both moisture transport and evapotranspiration.
KeywordsMoisture Flux Moisture Convergence Water Vapor Flux Moisture Flux Convergence Recycling Ratio
The authors would like to express their gratitude to Prof. S.E. Nicholson of Florida State University for providing Jackson et al. (2009), Prof. G. I. Burde of Ben-Gurion University of the Negev for assessing to Burde et al. (2006, 2006); They wish to acknowledge very fruitful discussions with Prof. P.J. Lamb of the University of Oklahoma, and for providing Zangvil et al. (2004). We also acknowledge the helpful comments provided by the reviewers.
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