Analysis on the Causes of Severe Drought in North China in Winter of 2008-2009

Abstract

A severe drought occurred in north China in winter of 2008-2009,and it resulted in serious economic loss and social problems,especially in Shanxi,Hebei,Henan and Anhui provinces.The NCEP/NCAR reanalysis data downloaded from the Earth System Research Laboratory of NOAA and the mean monthly precipitation data observed by 160 meteorological stations are used to research the abnormal change of air temperature,vertical air vapor content and air vapor transport during the severe drought.The results are as follows:(1) In winter of 2008-2009,air temperature was relatively high in central China and north China but low in the northern part of north China;(2) The vertical air vapor content was lower than the multi-year average over the Indian Ocean,southwest China,central China and north China during the severe drought,airflow transport was nearly straight over the most regions of China so that it was weaker than the average;(3) During the severe drought,there were the continuing block high over the Balkhash and Ural regions,pressure trough over the Lake Baikal region,and high over East Asia.The main airflow over Central Asian and East Asian was a meridional circulation.The circulation fields were conducive to the southward cold air to north China;(4) Subsiding airflow was stronger than the multi-year average over the most regions of China.Vapor transport from the Indian Ocean was weakened by the strong subsiding airflow over the Qinghai-Tibetan Plateau,southwest China and south China.These results can provide some theoretical bases and useful references for researching severe drought.