348-YEAR PRECIPITATION RECONSTRUCTION FROM TREE-RINGS FOR THE NORTH SLOPE OF THE MIDDLE TIANSHAN MOUNTAINS

<正> Correlation census shows that the correlation between the tree-ring chronologies in theUrumqi River Basin and precipitation during July in the last year to February in the concurrent yearis significant,and the best single correlation coefficient is 0.74,with significance level of 0.0001.Using two residual chronologies collected from west Baiyanggou and Boerqingou,precipitation for348 years can be reconstructed in the North Slope of middle Tianshan Mountains,its explainedvariance is 62%.According to much verification from independent precipitation data,historicalclimate records,glacier and other data.it shows that the reconstructed precipitation series of 348years is reliable.Analysis of precipitation features indicates that there were three wet periodsoccurring during 1671(?)—1692,1716—1794 and 1825—1866 and three dry periods during 1693—1715,1795—1824 and 1867—1969.Two wet periods,during 1716—1794 and 1825—1866,correspond to the times of the second and the third glacial terminal moraine formation,which is infront of No.1 glacier in Urumqi River source.According to computation,corresponding annualprecipitation amounts are 59mm and 30mm more than now.The reconstructed precipitation serieshas a significant drying trend from 1716 to 1969.and has better representativeness to theprecipitation of Urumqi and Changji Prefecture on the North Slope of Tianshan Mountains.