The existence and the climatological characteristics of the spring rainy period in Korea

摘要

The Spring Rainy period in Korea (SRK), a period with increased precipitation and higher rain frequencies than other periods before and after it, is defined as the period from the minimum to the first maximum value (from April 4 to May 16) of the Available Water Resources Index (AWRI), which is a sort of precipitation accumulated by daily weighted function. The most important characteristics of SRK associated with the precipitation increase are found as follows. Firstly, because it is the season that Northwestern Pacific High (NPH) makes its first northwestward expansion, zonal temperature gradient between land and ocean grows gradually and reaches the maximum through the year at the end of SRK, and become the cause of the precipitation increase. Secondly, because the cold northwesterlies over the Korean peninsula weakened gradually only at the lower levels (especially at 850 hPa level) and changed into westerlies or southwesterlies with warm advection, the air layer over this region becomes more unstable than the periods before and after it. As a result, this study provides the basis of connection on the existence and definition of summer monsoon as well as spring rainy period in the North-East Asia. Besides, the seasonal evolution around SRK and its connection to other seasons Such as Dry Period before Changma in Korea, Spring Persistent Rain in China and summer monsoon in East Asia are summarized. Copyright (C) 2005 Royal Meteorological Society.