2011年7月七大江河流域气候特点及降水异常成因分析

利用国家气候中心723站降水和气温资料、JRA-25和NCEP/NCAR I再分析资料数据集、NOAA气候预测中心海温资料等,采用线性趋势、动力诊断、相关分析、小波分析等方法,开展2011年7月我国七大江河流域气候特点及其变化特征研究,揭示长江流域主汛期降水异常的可能机理。结果表明：2011年7月七大江河流域降水量总体偏少,长江流域降水属异常偏少;流域气温持续气候变暖特征,以松嫩流域异常偏暖最为显著。降水变化线性趋势显示：珠江流域和长江流域为线性增加型;淮河流域为基本不变型;辽河流域、海河流域、黄河流域和松嫩流域为线性减少型。但降水具有显著年际变化外,长江流域、淮河流域、海河流域、黄河流域等具有显著年代际变化周期。2011年7月长江流域降水异常偏少的主要原因：大气对赤道中东太平洋外强迫的响应持续着La Nina的形态;副热带高压异常活动与东亚南风环流强度指数偏弱;长江流域整层水汽收支显著亏损,降水效率低。

Study on Climate Characteristics of Seven Great River Valleys and Mechanism of Precipitation Anomaly in July 2011

Based on the precipitation and temperature data at National Climate Centre 723 stations, the JRA 25 and NCEP/NCAR I reanalysis data sets and the NOAA Climate Prediction Centre extended reconstructed SST data, using methods of linear trend, dynamical diagnosis, correlation analysis and wavelet analysis, the climate characteristics and variation features of seven great river valleys (SGRV) in July 2011 were researched, and the mechanism of precipitation anomalies of the Yangtze River Valley (YRV) during the dominant flood season was revealed. Results indicated that the precipitations of SGRV were overall less in July 2011, however, the precipitation of YRV was far less than normal; meanwhile, the temperatures of SGRV were characterized by continued climate warming, especially for Songhua River Valley. The linear trend of precipitation changing showed that Zhujiang River Valley and YRV were in a linearly increased trend, Huaihe River Valley maintained an unchanged condition, and Liaohe, Haihe, Huanghe and Songhua River Valleys where in a linearly decreased trend. In addition to the obvious interannual variability, the decadal changes of precipitation in YRV, Huaihe, Haihe and Huanghe River Valleys were also obvious. The main causes for the below normal precipitation of YRV in July 2011 were as follows: The atmospheric responses to external forcing of equatorial Middle Eastern Pacific were the same as those to La Nina pattern; the subtropical high was abnormal and the East Asian southerly wind circulation intensity index (IES) was weak; besides, the water vapor budget had a deficit and the precipitation efficiency was low.