近40年青海东部春季降水变化特征及小波分析

应用线性趋势分析和小波变换分析方法对青海东部地区12个气象台站1961~2004年春季降水的变化特征及时~频特征进行了分析。结果表明:近44 a来,青海东部地区春季降水量波动明显,年代际变化表现出20世纪60年代偏多,70年代、80年代偏少,进入90年代以来偏多的趋势;春季降水总体呈弱的增加趋势,分阶段分析,只在1981~2004年时段趋势呈弱的减少,其余时段均呈增加趋势;在10 a及以上相对较大的时间尺度上,春季降水干、湿交替的特征非常明显,经历了6个干、湿交替的阶段,其突变点为1964年、1975年、1983年、1993年、2001年,其10~12 a和16 a左右的周期较为明显;而对于10 a以下相对较小的时间尺度,春季降水变化比较复杂,增加了更多的相对干、湿交替阶段和突变点,其6~8 a的周期突出;当周期振荡表现为较强的负位相时,均会发生强的干旱;从最近几年青海东部地区的春季降水变化来看,其较大尺度和较小尺度的变化均处于较强的偏多期。

The evolvement characteristics and wavelet analysis of spring precipitation of last 40years in east Qinghai

Based on the spring precipitation data of 12 observatories in 1961-2004 in Qinghai province,the variation characteristics of spring precipitation on Qinghai plateau is analyzed,and the time-frequency characteristics of spring precipitation over Qinghai agricultural area is also analyzed by using linear trend analyze method and wavelet analysis method.The results show that the spring precipitation over the east area of Qinghai plateau had outstanding wavy character;its variation was large in the 1960s and 1990s and little in the 1970s and 1980s.The spring precipitation over the east area of Qinghai plateau generally increased weakly.From the 1980s to now,the spring precipitation decreased weakly,but increased in the rest of time.For the large time scale of equal to or more than 10 years,the characteristic of dry/wet-vicissitude in spring over the agricultural area of Qinghai was very significant in last 44 years,and 6 dry/wet-vicissitude periods occurred during these years,the replace point appeared in 1964,1975,1983,1993,and 2001,the period of 10-12 and 16 years is obvious.The variation of spring precipitation for the time scale below 10 years over the agricultural area of Qinghai in last 44 years was rather complicated,the replace point and the relative wet/dry-vicissitude periods got more often,the period of 6-8 years was very clear.Heavy drought stage usually appeared when the whole oscillation period was heavy negative phase-shift.In recent years,the spring precipitation change over the east area of Qinghai plateau has got more often in both the large time scale and the short time scale.