树木年轮记录的天山北坡中部过去338a降水变化

The Recent 338-yearPrecipitation Series Reconstructed from Tree-ring in Northern Slope of Tianshan Mountains

利用位于天山北坡中部9个气象站的降水资料与采自该地区的21个树木年轮年表序列进行分析。结果表明,9个气象站上年8月到当年7月的平均降水量与树木年轮标准化年表具有很好的相关性,最高单相关达到0.612(P<0.0001)。分析发现,生长季前期及春材形成期的降水变化对天山山区树木年轮径向生长量起着决定性作用。用四工河东白杨沟、呼图壁河赛热克巴依萨依、呼图壁河希热克久热特、四工河西白杨沟、奎屯河兰能果尔南5个标准化年表较好地重建了天山北坡中部近338a来上年8月到当年7月的降水量,重建方程的方差解释量达到60.0%,经过统计检验和历史资料验证,表明重建序列是可靠的。对过去338a天山北坡中部降水变化的特征分析表明,近338a间,天山北坡中部降水大体经历了8个偏干和8个偏湿阶段,偏湿年份与偏干年份基本持平。最长的偏干阶段是1705—1750年,最干旱的阶段为1960—1989年,最干旱年份是1796年、1944年和1974年,降水偏少程度均大于27%;最长的偏湿阶段是1917—1959年,1690—1904年间为降水最为丰沛的时期。天山北坡中部338a降水具有两年左右的变化准周期,在1751年发生了明显的由少到多的突变,在1958年前后发生了明显的由多到少的突变。

Analysis on correlation between the precipitation data of 9 weather stations and the 21 tree-ring standardization chronologies in northern slope of Tianshan Mountains showed that the correlation was significant between chronologies and the precipitation series from last August to July,with a maximum correlation coefficient of 0.612（P0.0001）.The annual precipitation series in recent 338 years were reconstructed based on five tree-ring standardization chronologies,and the reconstruction equation could explain variance of 60.0%,and statistical test and historical data validation indicated that the equation reconstructed was credible.Analysis of the precipitation series in the recent 338 years showed that the reconstructed precipitation series had 8 wet periods and 8 dry periods.The longest stage of dry years was 1705—1750,the most dry phase was 1960—1989,the most dry years were 1796,1944 and 1974,and the rainfall was 27% below normal;the longest stage of wet years was 1917—1959,the precipitation of 1690—1904 was most abundant.The reconstructed precipitation series in the recent 338 years had variation period of 2-a,the abrupt changes of precipitation occurred in 1751 and 1958.