1961-2011年西北地区春季降水变化特征及其空间分异性

利用西北地区121个气象站1961-2011年降水量资料, 分析了西北地区春季降水的基本气候特征;通过EOF、REOF、功率谱等方法, 对西北地区春季降水的时空特性进行了研究, 用Mann-Kendall检验法检验西北地区春季降水序列是否存在突变现象.结果表明: 西北地区春季降水空间分布极不均匀, 其空间分布特征是东南部和西北部为多雨区、中间为少雨区.西北地区春季降水在第一空间尺度上为全区一致, 在第二空间尺度上可分为2个自然气候区, 在第三空间尺度上可分为6个自然气候区.从年代际变化来看, 1980年代是近半个世纪来降水最多的10 a, 1970年代是降水最少的10 a;西北地区春季降水的年际变率十分显著, 降水最多的年份是最少年份的3倍多. 1961-2011年间西北地区春季降水发生了明显的突变: 1973年出现了一次趋于减少的突变, 1985年出现了一次趋于增多的突变. 18~19 a的长周期是其主要周期, 其次是5 a和7 a的短周期. 未来20 a西北地区春季降水量呈缓慢下降的趋势.

The Changing Characteristics of Spring Precipitation in Northwest China and Their Spatial Differentiation During 1961-2011

Using the precipitation data from 121 representative observation stations in Northwest China from 1961 to 2011, the characteristics of spring precipitation were analyzed. EOF, REOF and power spectrum method were used to research the spatial and temporal characteristics of spring precipitation in Northwest China. Whether there were mutations in the spring precipitation sequence was tested by Mann-Kendall test. The results show that the spatial distribution of spring precipitation in Northwest China was extremely uneven. One can see that the rainy areas located in the southeast and northwest, and the less rain areas located in the middle. Spring precipitation was consistent in the entire region at the first space scale, two natural climate zones could be recognized with the second space scale, and six natural climate zones could be recognized with the third space scale. The 1980s was the most precipitation decade among the five decades. The 1970s was least precipitation decade. The annual variability of spring precipitation was significant in Northwest China. Precipitation in most precipitation year was three times more than that in least precipitation year. There were obvious mutations in spring precipitation in Northwest China from 1961 to 2011. An abrupt decreasing occurred in 1973, and an abrupt increasing occurred in 1985. As regards of changing cycles, there was a long period of 18 19 years (the main) and short periods of 5 years and 7 years. It is expectancy that spring precipitation in Northwest China would be slowly coming down in the future 20 years.