Characteristics of moisture flux convergence in Central Southwest Asia

The National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR) reanalysis data have been used to compute the moisture flux convergence (MFC) over Central Southwest Asia (CSWA) between 45 degrees-75 degrees E and 25 degrees-40 degrees N. The present study focuses on the 1969-2007 period, and both horizontal distributions and vertical profiles of MFC have been calculated and compared. Moisture is transported into the region from the west throughout the year. In this region, winter is the wettest season with the most precipitation. Areas of high moisture convergence are observed in the cast and southwest. Moisture convergence in the east and southwest are associated with topographic effects. Our study also examined composites of moisture flux convergence that characterized the wettest and the driest years in this area. The magnitude of the monthly MFC differs considerably between these two extremes. The spatial distribution of moisture flux convergence during the recent drought period (1999-2001) was also examined in order to understand how moisture transport affects drought. Deficiency of precipitation during drought periods appears to be due to deviation of moisture transport away from the region.