Characteristics of Droughts in Spring and its Relationship with Water Vapor Transportation in South China

By using the precipitation data of 47 basic stations in South China and the water vapor transport flux calculated from the NCAR/NCEP II reanalyzed data from 1979 to 2005,the characteristics of droughts in South China in spring and its relationship with water vapor transport flux are studied.The results show that precipitation in South China in spring can be partitioned into two classes.Region I,located in the east of 110.5 °E,is characterized by the first class,showing an outstanding decreasing trend in rainfall.Region II,located in the west of 110.5 °E,is marked by the second class with unconspicuous decreasing tendency in reainfall.In 1994,there was an abrupt decrease in rainfall in region I.The moisture source of South China is located in the South China Sea and western Pacific Ocean.The water vapor is transported to South China via the southern Indochina peninsula.When the southern water vapor transport is weaker/stronger over the central and northern South China Sea,the precipitation in region I correspondingly becomes weaker or stronger and droughts or floods develop.While the southern moisture transport is weaker or stronger over the southwestern South China Sea and southern Indochina peninsula,droughts or floods prevail in region II.