Seasonal changes in wind systems relating to precipitation during the rainy season in the Loess Plateau, China

Abstract

The Loess Plateau in China is a typical summer precipitation region with a rainfall season from May to September. We analyzed the seasonal variations in precipitation and wind systems transferring water vapor into the Loess Plateau using data averaged for 14 years from 1979 to 1992. The monthly average precipitation was analyzed using data provided by the National Center for Atmospheric Research (NCAR). The wind vector, geopotential height, and water vapor transport were calculated from the National Centers for Environmental Prediction/National Center for Atmospheric Research (NCEP/NCAR) reanalysis data. There are some differences in the wind system during the rainy season, which cause rainfall over the Loess Plateau. Southwesterly winds originating from the Bay of Bengal reach the Loess Plateau due to the large pressure gradient in south and north China in July. This wind system transports a large amount of water vapor into the northeast of the Loess Plateau. In August, water vapor is transported into the Loess Plateau by south easterly winds from the Pacific Ocean anticyclone as the southwesterly wind over china weakens. Thus, the wind system transporting water vapor into the Loess Plateau changes from the southwesterly winds from the Bay of Bengal to the southeasterly winds from the northwest Pacific Ocean between July and August.