Research On Arid In The Sichuan-Chongqing Area In Summer

The world's extreme cases of high temperature and drought occurred frequently with the characteristics of high strength and large scale and so on since the 90's of 20th century.According to statistics,the losses caused by meteorological disasters accounted for about 85 percent in all losses caused by natural disasters,while the drought has accounted for about 50 percent. Therefore,the research on the decade's variability of summer drought and the influence caused by atmospheric circumfluence shows great meanings in the understanding of summer drought in Sichuan and Chongqing region.This article has test and compared three indexes of flood and drought by the use of daily data of temperature and precipitation of 178 stations in Sichuan-Chongqing region from 1961 to 2007.The CI index can reflect the daily variability of flood and drought,so it shows the dynamic evaluation and better prediction of beginning-ending day of drought as its worse flood monitoring.The Z index can reflect situations of flood and drought well,so it can be used to predict flood and drought which measured by monthly or seasonal scale.According to the Z index modified,normal situation without flood and drought accounts for about 40%,situation of close to flood and situation of close to drought account for about 15%each other,situation of flood and drought accounts for about 10%,while the situation of heavy drought and heavy flood account for about 5%.The Z index modified fit the division of degrees of flood and drought,and it matches the distribution of real situation that the driest years when were 1972,1994,1997 and 2006 placed 2nd,4th, 3rd and 1st in the history,equally the most flooded years when were 1981 and 1998 placed 2nd and 1st.It's obviously that the flood and drought of Sichuan-Chongqing region in summer has a 25-years discipline on this basis through the analysis of the decade's variability of summer drought analyzed by Wavelet Analysis and statics,and also has a 3-5years vibration.The precipitation of Sichuan-Chongqing region in summer has changed obviously twice,it declined from the middle of 60's to 70's,then increased from in 70's, afterwards decreased from 90's till now when got the worst in 2006.On the other hand,we found that the serious catastrophe of high temperature and drought in Sichuan-Chongqing region in summer 2006 may be caused by the Abnormal atmospherics circulation of which the western Pacific subtropical high extended farther westward and northward strongly,the stable Iran high extended farther eastward strongly were the important factors, as the earlier seasonal variation of southern high did.Anything else,the disaster of high temperature and drought in Sichuan-Chongqing region in summer 2006 was also related to the influences of typhoon,less snow on plateau and stronger heating situation.