中国黄土高原区域性暴雨时空变化及碎形特征

利用黄土高原51个测站40年日降水资料,采用REOF分析、小波分析和分维分析等方法,研究了该地区区域性暴雨的时空特征。结果表明:黄土高原区域性暴雨事件趋于减少,过程雨量加大;区域性暴雨频数演变存在4年和7~8年的振荡,以4年周期为主;在1977年区域性暴雨事件出现突变性减少,相应的短周期减弱、长周期加强。分析表明,区域性暴雨事件骤减与500 hPa高度、副热带高压和青藏高压位置关系密切;与区域性暴雨事件伴随的全区降水量存在6个空间型,各型暴雨雨量异常具有客观碎形(分形)特点,其中黄土高原西北部和东南部暴雨雨量异常偏多的分维数值较小,在黄土高原中部分维数值较大,反映出黄土高原中部暴雨异常偏多的非线性机制最为复杂,而西北部和东南部地区相对简单。

The Characteristic of Fractal and Variation in Regional Rainstorm over China Loess Plateau

Using the daily precipitation data at 51 stations over China Loess Plateau in recent 40 years,with REOF,wavelet and fractal imension methods,the spatial and temporal characteristic of regional rainstorm in the region are analyzed.The results showed the events of regional rainstorm decreased,process rainfall increased,it had remarkable 2 phases and a jump-point.Ones variation period occurred abrupt change that contacted with the longitudinal positions of SH(the longitude of west end of SH based on the contour of 5860 gpm),the Qinghai-Xizang high(the longitude of east end of Qinghai-Xizang high based on the contour of 16760 gpm).Six divisions were identified.The fractal dimension of anomalous rainfall of rainstorm was 0.8378~0.9242.Minimum fractal dimension was in the southeast of the China Loess Plateau,maximum fractal dimension was in the hinterland of the plateau.