西北地区近50年降水周期的稳定性分析

A Study of the Stability of the Precipitation Cycle over Northwest China in the Past 50 Years

用小波分析和奇异谱分析两种方法相结合对西北地区26个站1951-1999共49年的降水周期随时间的变化进行了分析.结果表明： 西北地区降水周期随时间变化具有较强的区域性;宁夏陕北地区和河西走廊地区近50年的降水变化趋势呈反位相关系;根据近30年西北地区降水变化形式,西北地区大致可分为3种类型的降水变化：①不稳定变化型（新疆地区）;②过渡型（河西走廊地区）;③稳定型（宁夏陕北地区）.近50年西北地区降水普遍存在的准3年左右的周期在20世纪70～80年代显著性下降,5～7年左右的周期和9～14年左右的长周期也随时间有着不同的变化;即各地区所有周期成分的稳定性都显著性地随时间发生变化,各地降水普遍存在一个相对比较稳定的但不太显著的10年左右的平衡态.表明西北地区的降水随时间变化具有多平衡态和非周期性振荡的特点.但西北大部分地区都存在某一特定的周期成分,在该固定周期成分出现前后,其振幅变化与该地区降水趋势变化之间存在着密切关系.

Using wavelet analysis and singular spectrum analysis（SSA） ,precipitation of 26 stations over northwest China during 1951-1999 are analyzed. There is a stronger regional feature of precipitation over western China. Between the Hexi corridor area and the area which includes the Ningxia and the north Shaanxi provinces, there is a reverse trend. Various precipitation in northweastern part can be divided into three precipitation types. According to the precipitation change feature in past 30a over northwest China, the three types are： sharp change （Xinjiang areas） ; transitional （Hexi corridor area） ; stable type （it includes the Ningxia and the north Shan＇xi provinces）. It shows that the precipitation of every area has the different response to the global warming. The northwest Chinag precipitation, in common, has a period of 3a and 5 -Ta, while it exists for 9 -14a long period. The periods＇significations are changed in spatial-temporal. On the other words, there are many different balance states and it becomes unstable for the precipitation with time. There is inherent period length in every area of the northwest China, while the inherent period occurrs, its various amplitude change better relate to the precipitation trends.