Precipitation Variations and Drought Causes in the Cold Half of the Year in the Pearl River Delta Region during the past 38 Years

Based on the historical records of monthly precipitation from 22 weather stations in the Pearl River Delta region from 1970 to 2008,this paper used running mean,EOF analysis and wavelet analysis to document precipitation variations and drought causes in the cold half of the year.The precipitation variations during the cold half of the year in the Pearl River Delta region show a highly synchronization,with a cycle of 6～7 years.The precipitation in the cold half of the year may reduce in the near future.The main reasons for drought during the cold half of the year in the Pearl River Delta region are weak polar vortex,strong European trough and ridge near the Balkhash Lake,active cold air,inactive westerly wind disturbance in the low-mid latitudes,weak southern branch trough,and less confrontation between cold and warm airs.