1971——2010年中国西北地区秋季降水变化特征

本文采用1971—2010年9—11月逐月NCEP/NCAR再分析数据和国家气候中心全国台站资料，通过常规统计分析、趋势分析、Morlet小波变换、M-K 检验以及奇异值分解，对中国西北地区秋季降水量与降水日数两个方面进行了较为详细的分析，得到了较为全面的中国西北地区秋季降水时空分布特征，并分析了500 hPa环流异常对其可能的影响。结果表明：1971—2010年间西北地区秋季降水量与降水日数均为上升趋势，相对来说，秋季降水日数在这40年间的变化趋势更为显著；西北地区秋季降水量及降水日数整体呈现出增加的趋势，主要是受青海、甘肃两省大部分站点的降水量及降水日数明显增多引起的；西北地区秋季降水量、降水日数变化幅度较大区主要位于青海东南部与陕西南部；降水日数在未来将会有减少的变化趋势；500 hPa东高西低的异常环流形势越明显，甘肃东南部、宁夏、陕西大部秋季降水量越大，北高南低的异常环流形势则在中国西北地区大部易造成秋季降水量偏多。

Variation of Autumn Precipitation in Northwest China in 1971-2010

Based on two indices of precipitation and precipitation days, the spatial and temporal variation characteristics of autumn precipitation in Northwest China were analyzed using the NCEP/NCAR reanalysis data and meteorological station observation data from 1971 to 2010 by routine statistical analysis, trend analysis, M-K test, singular value decomposition. Impacts of 500 hPa atmospheric circulation anomalies patterns on autumn precipitation were analyzed too. Results indicated that both autumn precipitation and autumn precipitation days in 1971-2010 increased, but autumn precipitation days increase was relatively more significant in past 40 years. Both autumn precipitation and autumn precipitation days in Northwest China were influenced by significant increase of autumn precipitation and autumn precipitation days in most meteorological stations in Qinghai Province and Gansu Province. Variation of autumn precipitation and autumn precipitation days in Northwest China was more significant in South-eastern Qinghai Province and Southern Shaanxi Province. The autumn precipitation was great in Southeastern Gansu Province, the Ningxia Hui Autonomous Region and Shaanxi Province when the east-high and west-low atmospheric circulation anomaly at 500 hPa was strong, and the autumn precipitation was great in most parts of Northwest China when the south-high and north-low atmospheric circulation anomaly at 500 hPa was strong.