东亚冬季风异常与广东前汛期旱涝关系的初步分析

利用500hPa北半球格点资料,参照历史平均东亚大槽位置,定义了东亚冬季风强度指数(I₅₀₀)。分析发现,近50年东亚冬季风强度有减弱趋势,特别是1987年以来冬季风明显减弱。根据广东48个站1954～2004年前汛期(4～6月)降水资料,用区域旱涝指数W对广东前汛期旱涝等级进行划分。51年内广东有9年前汛期出现大涝(或特涝),11年出现大旱(或特旱),旱涝发生频繁。冬季风异常对广东前汛期降水的影响比较大,强冬季风年后广东前汛期出现大旱的可能性较大,而出现大涝的可能性很小。

Preliminary Researches of the Relationship Between Anomalous Winter Monsoon Circulation over East Asia and Flood/Drought from April to June in Guangdong

Based on 500 hPa geopotential height fields and mean position of East Asian trough,a definition of the East Asian winter monsoon index(I_(500)) is given.The analysis of I_(500) that the winter monsoon undergo a pronounced reduction during the past 50 years.Since the year of 1987,the winter monsoon has become rather weakened.Using the seasonal precipitation data of 48 stations in Guangdong from 1954 to 2004,the grades of drought and flood from April to June are marked off and analyzed by the regional drought and flood index(W-index).Results show that there are nine severe flood years and ten severe drought years in the past 51 years.The effect of abnormal winter monsoon on the precipitation from April to June is obvious.The strong East Asian winter monsoon usually leads to severe drought.