1960-2014年中国绿洲严寒期的时空变化特征与成因分析

基于中国绿洲74个地面气象站的逐日平均气温观测资料,计算候平均温度≤ 0 ℃的严寒期起止候及候数,运用线性趋势法、M-K突变检验、Morlet小波分析法、相关分析等方法,分析中国绿洲严寒期的起止候及候数的时空变化特征与成因。结果表明：近55年来,中国绿洲严寒期起始候推后、终止候提前、候数缩短,变化倾向率分别为0.3 p/10a、-0.27 p/10a和-0.58 p/10a;且空间差异显著,其中,柴达木盆地绿洲严寒期来的最早、结束的最晚,严寒期变化趋势最显著。严寒期起止候及候数分别在1990年、1998年、1994年发生突变。严寒期起始候与候数表现出与大气环流和厄尔尼诺有关的显著周期,终止候表现出与太阳活动有关的显著周期,可以证实严寒期起始候和候数的变化与大气环流和厄尔尼诺密切相关,而终止候的变化则与太阳活动有关。青藏高原指数、亚洲区极涡面积指数和二氧化碳排放量是影响研究区严寒期的主要因子,而南亚夏季风指数则对柴达木盆地绿洲影响最显著。研究区严寒期随着经纬度和海拔高度的增加,起始候提前、终止候推后、候数延长,并以纬度的变化最显著。严寒期起止候及候数对区域增暖具有极好的响应,但区域增暖对起止候及候数的影响各不相同。

Spatial and temporal variations and their causes for the cold period in China's oases during 1960-2014

Based on the daily average temperature of 74 meteorological stations in China's oases of observation data, we calculated pentad average temperature ≤0℃ of the onset and upset pentad and pentads of cold period by using the methods of linear regression analysis, nonparametric Mann- Kendall test, wavelet analysis and correlation analysis. We also analysed the spatial and temporal variations and their causes for the onset and upset pentad and pentads of cold period in China's oases. The results show that: in recent 55 years, the onset pentad of cold period postpones and upset pentad advances, the pentads shorten gradually, the trend rates are respectively 0.3 p/10a, -0.27 p/10a and -0.58 p/10a; and the spatial difference is significant, especially for the Qaidam Basin oases, the onset pentad is the earliest, the upset is the latest, and the change trend of cold period is the most obvious. Mutation point of the onset and upset pentad and pentads of cold period is respectively observed in 1990, 1998 and 1994. The onset pentad and pentads of cold period show an aperiodic cycle, which is related to the atmospheric circulation and El Nino events, while the upset pentad of cold period shows an aperiodic cycle, which is related to the solar activity, suggesting that the onset pentad and pentads of cold period are closely related to the atmospheric circulation and El Nino events, while the upset pentad of cold period to the solar activity. The Qinghai-Tibet Plateau index, the Asia polar vortex area index, and the carbon dioxide emissions are the main factors affecting the cold period of the study area, and the South Asia summer monsoon index exerts the greatest effect on the Qaidam Basin oasis. The onset and upset pentad and pentads of cold period increase with the increase of latitude, longitude and altitude, onset pentad advances and upset pentad postpones, the pentads extends gradually, and the change of latitude is most significant. The onset and upset pentad and pentads of cold period have good response to regional warming, but the regional warming has different effects on the onset and upset pentad and pentads of cold period.