近48a宁夏寒潮的变化特征及可能影响的成因初步分析

利用1961—2008年宁夏日温度及逐月北半球500 hPa环流特征量、北极涛动指数(AOI)和NCAR/NCEP再分析资料,对宁夏寒潮频次变化的气候特征进行了分析,并对影响其变化的可能原因进行了讨论,结果表明:宁夏寒潮活动各地差异较大,主要出现在春季;近48年,春秋季寒潮频次呈弱增加趋势,冬季呈弱减少趋势;寒潮频次与AOI、气温呈负相关,与西伯利亚高压、东亚冬季风强度及入侵中国的冷空气活动频次呈正相关,相关关系在秋冬季明显,春季不明显;在气候变暖的大背景下,从20世纪80年代末开始,随着AOI从负位相转为正位相,冬季西伯利亚高压和东亚冬季风强度的减弱使得宁夏地表温度持续升高,是宁夏冬季寒潮频次减少的可能原因;春季也有类似的变化,不同的是:20世纪80年代中期以前,西伯利亚高压对寒潮活动作用更显著,之后,随气温持续增暖,冷空气活动对寒潮频次的影响更明显;秋季,西伯利亚高压和冷空气活动对寒潮的影响更直接明显。研究还发现,进入21世纪后,随着全球持续增暖,北极涛动对西伯利亚高压和东亚冬季风的影响有所减弱。因此,北极涛动、西伯利亚高压、冷空气活动频次、东亚冬季风、气温这几者之间的相互反馈作用是宁夏寒潮频次变化的可能原因。

Variety of Ningxia Cold Waves in the Last 48 Years and Its Possible Reasons

By using the daily surface temperature data of Ningxia, monthly characteristic values of 500 hPa circulation of the Northern Hemisphere, Arctic Oscillation Index (AOI) and NCEP/NCAR reanalyzed data during 1961-2008, the climatic characteristics of the variety of cold waves in Ningxia are analyzed, and the possible reasons for it are further discussed. The result indicates:the cold wave activities are distinct different in Ningxia different regions, and mainly occur in spring; in the recent 48 years, cold waves in Ningxia increased slightly in spring and autumn, decreased slightly in winter; the frequency of cold waves in Ningxia has negative correlation with AOI and temperature, positive correlation with the intensity of Siberian high, East Asian winter monsoon and the frequency of cold air activities invaded China, and the correlativity is obvious in autumn, winter and inconspicuous in spring; under the background of global warming, with the phase of AOI transformed from negative into positive from the end of 1980s, the intensity of winter Siberian high and East Asian winter monsoon has weakened, and made the surface temperature continue rising in Ningxia, this is one of the possible reasons for the decrease of Ningxia cold waves in winter; in spring, there has the similar variety but differs in the following points:the Siberian high played a more significant role in cold wave activities before the mid-1980s, while the impact of cold air activities on cold waves was more obvious with the continuou temperature rising after then; meanwhile, the Siberian high and the cold air activities impacted the cold waves more directly and more obviously in autumn. Studies also found, that with continued global warming, the impact of Arctic Oscillation on Siberian high and East Asian winter monsoon has weakened after the 21st century. Therefore, the mutual feedback among the Arctic Oscillation, Siberian high, the frequency of cold air activities, the East Asian winter monsoon and temperature is the possible reason for the variety of Ningxia cold wave frequency.