甘肃南部公元1824年以来降水重建

PRECIPITATION RECONSTRUCTION IN SOUTHERN GANSU PROVINCE SINCE A.D.1824

通过对甘肃南部腊子口的油松(Pinus tabulaeformis)进行树木年轮分析,首次建立了研究区1824~2011年标准化年表(STD),并与邻近的岷县气象站降水和温度进行相关分析,结果表明,该年表与上一年8月到当年7月的总降水(p8c7)相关性最好,相关系数达到0.644(p<0.01)。据此建立树轮指数与降水量之间的转换方程,该方程解释了实测期41.5%的降水(1952~2008年),并通过一系列稳定性检验,进而重建研究区1824~2011年间188年以来的降水。对重建结果进行11年滑动平均,结果表明,共出现3次极干旱期,分别为1900~1902年,1926~1930年和1997~2000年,尤以1997~2000年最为严重,极干旱期占到重建期的6.38%,而极湿润期只有1937年,仅占0.53%。与邻近区已有的研究对比后发现,1920s^1930s干旱事件在研究区以北区域更为严重。重建结果与赤道东太平洋、中太平洋平均海表温度(SST)呈显著负相关(p<0.1),说明研究区干旱变化与海温存在遥相关关系;多窗谱分析(MTM)结果表明降水存在2~3年和7年周期。ENSO事件时,东亚季风减弱,位于季风边缘区的甘肃南部地区出现干旱化趋势。

A Pinus tabulaeformis tree ring width standard chronology（STD） ranging from 1824 to 2011 was established based on the tree cores collected from Lazikou （ 33.39° - 34.20°N, 102.55° - 104.04°E） , southern of Gansu Province. Statistical analysis showed that the chronology are positively correlated to the precipitation from previous August to current July（ r = 0. 644, p〈0.01 ）. We have reconstructed the precipitation from 1824 to 2011 based on the relationships between the chronology and the precipitation. The reconstruction explains 41.5% of the actual precipitation variance during the common period 1952 - 2008. The 11 years moving average of the reconstructed precipitation showed that the serious drought periods are separately 1900- 1902, 1926 -1930 and 1997 -2000, especially 1997 - 2000 is most critical serious period. The wettest period is 1937. We found that 1920s - 1930s drought is much more serious in the northern part of the research area compared to other reconstructed results. The reconstructed results were negatively correlated to the east and middle Pacific Ocean sea surface temperature （SST）. The multiple spectral peaks are identified at 2 -3 and 7 years. Our results suggested that the drought is tele-connection with the sea surface temperature （SST） in the research area. The serious drought happened in the south part of the Gansu Province,when the ENSO break out and the weaken East Asia monsoon periods.