近50年黄河上中游降水多时间尺度特征分析

Multiple Time Scales Characteristic of Precipitation in Recent 50 Years of Upper and Middle Reach of Yellow River

摘要: 利用1961~2011年黄河上中游45站年、月降水量资料，通过计算气候倾向率、降水指数γ、降水集中度和集中期等，对该区降水年际变化和年内分配特征及其演变趋势进行诊断分析。结果表明：1) 黄河上中游区年降水量自东南向西北迅速递减，并且存在两个降水变化敏感区：黄河源区和陇中–陇东黄土高原区。黄河源区年降水量呈增加趋势，而陇中–陇东黄土高原区干旱化趋势明显。2) 400 mm等值线在黄河源区与黄河中游区的移动趋势和轨迹存在明显差异。黄河源区该线总体呈向北移动的趋势；黄河中游区2000年以前该线向东南方向移动的趋势显著，2000年以后则向西北方向回归。3) 黄河上中游降水季节分配变化趋势总体为春、夏季降水明显减少，而秋季降水显著增多，特别是2000年之后。而不同区域各季降水的变化趋势不尽相同，关中平原是降水季节分配变化最明显的区域。4) 黄河上中游区降水集中期总体都在7月，黄河源区集中期略早于黄河中游地区。降水集中度由东南向西北递增。全区集中度在1998年以前年际波动较大，1998年以后趋于稳定且接近均值。

Abstract: Based on the yearly and monthly precipitation data of 45 stations from 1961 to 2011 over the up-per and middle reach of Yellow River (UMRYR), by the method of climate tendency rate, precipita-tion index, concentration degree and period, the precipitation interannual variation and distribu-tion characteristic and its evolution trend were analyzed. The results show that: 1) The annual precipitation rapidly declines from southeast to northwest, and there was a rain shadow area from Lanzhou to Huining of middle Gansu province. The two climate change sensitive areas were source area of the Yellow River and middle and east of Gansu loess plateau. The precipitation increased in source area of the Yellow River, mean value of climate tendency rate was 9.5 mm/10a. The drought trend was obvious in middle and east of Gansu loess plateau, average value of climate tendency rate was −23.4 mm/10a. 2) There were significant difference of mobile trend and track of 400 mm rainfall contour between source area and middle reach of the Yellow River. In source area of the Yellow River, the trend of 400 mm rainfall contour moved north, but in middle reach of the Yellow River the contour obvious moved southeast before 2000, and regressed to northwest after 2000. 3) The general variation trend of seasonal distribution of precipitation in UMRYR were that the precipitation reduced obviously in spring and summer but increased significantly in autumn, especially after 2000. The variation trend of precipitation in each season was inconsistent in different areas, and the area where seasonal distribution of precipitation was obvious was Gu-anzhong plain. 4) The precipitation concentration period of UMRYR was in July, but concentration period of source area was slightly earlier than middle reach of the Yellow River. The precipitation concentration degree increased from southeast to northwest, and the value was between 0.45 - 0.71.