Precipitation Days Number Reconstruction by Using Tree Ring Width at the Southwest Edge of Junggar Basin

Tree ring width data from the four sampling sites which are located at the southwest edge of Junggar Basin are used to established width chronologies here. Correlation analysis betw een tree ring width index and climatic factors indicates that the radical grow th is dominated by moisture conditions. Tree ring width index is significantly positively correlated with precipitation and precipitation day 's number and negatively with temperature,in which,the correlation coefficient betw een tree ring width standardized indexes of HXC and precipitation days number from February to August is 0. 724. Because of the large slope and shallow soil of the sampling sites,the storage capacity of soil is weak. Heavy rain in grow th season make a great contribution to precipitation amount,which result that the correlation coefficient betw een tree ring width index and precipitation days number is higher than that betw een tree ring width index and total precipitation. The linear regression method was applied to build the transfer function betw een tree ring width standardized chronology and precipitation days number,and the explain variance reaches 52. 4%. Cross validation indicates the reliability and stability of the function. The drought history document in Yili,Tacheng and western part of northern slope of Tianshan Mountains was consistent with the reconstructed precipitation days. It also testified that reconstructed series could capture the drought events in the study area. Regional comparison betw een the reconstructed precipitation days at southwest edge of Junggar Basin and the precipitation history of Tianshan Mountains area and south slope of Tianshan Mountains reveals the reconstructed series in this study is more consistent with that in Tianshan Mountains.