湖南近50年极端连续降水的气候变化趋势

Climate variations of extreme continuous rainstorms in Hunan during 1960-2009

采用湖南88个地面气象站点1960～2009年的逐日降水资料运用一元线性回归、小波分析及M-K突变分析等方法分析了湖南极端连续降水的时空分布特征及变化趋势。此外,也运用NCEP再分析资料简要分析了影响湖南极端连续降水的因素。研究表明:湖南极端连续降水的高值区位于湘西北、湘东南和湘东北,其余地区为低值区。且湘北和湘西北部分站点极端连续降水的强度可能减弱,湘中和湘西南部分站点极端连续降水可能比原来更少,而其余地区极端连续降水均可能增多。在过去50年湖南极端连续降水事件增多、强度增大,尤其是进入1990年代以后。在1990年代到2000年代初极端连续降水增多是突变现象,且存在2～3年、4～7年和12～16年左右的周期振荡。地形和气流相互作用、是导致湖南极端降水空间分布差异的主要原因之一,湖南西部和南部山区的净获得水汽较北部和中部平原净获得的水汽多,这与湖南极端降水空间分布基本趋势比较吻合。

Using daily precipitation data of 88 stations from 1960 to 2009, the spatio-temporal distribution of extreme continuous rainstorms in Hunan is examined by linear regression, wavelet analysis and abrupt change analysis. In addition, the factors affecting rainstorms in Hunan are analysed using NCEP reanalysis data. The results showed that there are high value areas with extreme continuous rainstorms in northwestern, southeastern and northeastern Hunan, and low value areas in the remaining part of the province. And the intensity of extreme continuous rainstorms may weaken in northern and northwestern Hunan. Extreme continuous precipitation may become less in central, southwestern and northwestern Hunan, but occurs more frequently in other parts. The frequency of extreme continuous rainstorm events is increasing, and the intensity is aggravated. Generally, the extreme continuous rainstorms presented variations in three quasi-periods of 2-3a, 5-7a and 12-16a. The increase of extreme continuous rainstorms is characterized by abrupt changes from the 1990s to early 2000s. Interaction between topography and air flow is one of the main reasons for spatial difference of extreme continuous rainstorms in Hunan. Atmos- pheric moisture content and net gain of moisture in west and south mountainous areas is more than those in the central and northern plains. There is a good correspondence between the net moisture gain or net moisture loss and extreme continuous rainstorms distribution in Hunan.