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.