青藏高原东北部冷空气次数和强度变化的特征研究

Variation characteristics of cold air processes in northeastern Tibetan Plateau

利用青藏高原东北部68个国家气象站的气象资料,统计了1961—2015年的全区月、季、年冷空气次数、强度和强降温综合强度资料,应用气候诊断方法分析了冷空气次数、强度和强降温综合强度的变化特征及其成因。结果表明:在年尺度上,1961—2015年青藏高原东北部全区冷空气年平均出现次数为49.6次,冷空气次数气候变化倾向率每10 a减少0.600次,减少趋势不显著;全区冷空气年平均强度为0.39,气候变化倾向率每10 a降低0.022,减弱趋势显著;全区冷空气年强降温综合平均强度为0.67,气候变化倾向率每10 a降低0.005,减弱趋势不显著。在季节尺度上,冷空气次数夏季减少的趋势显著,而春季减少的趋势和秋季、冬季增加的趋势不显著;冷空气强度冬季减弱的趋势显著,而其他季节减弱的趋势不明显;强降温综合强度春季增强趋势和其他季节减弱的趋势不显著。1961—2015年大西洋欧洲区极涡面积指数等因子减小以及热带北大西洋海温指数等因子增大是导致全区年冷空气次数减少的主要成因之一,而西藏高原指数等因子增强和热带印度洋海温偶极子指数等因子减弱是导致年冷空气强度减弱的主要原因之一。

Based on the meteorological data from 68 national meteorological stations in the northeastern Tibetan Plateau,China,the monthly,seasonal and annual data about the frequency and intensity of cold air and strong cooling during the time period from 1961 to 2015 are summarized and the corresponding change characteristics and causes are analyzed with climatic diagnostic method.The results indicate that,on a yearly scale,the average frequency of cold air in the northeastern Tibetan Plateau in the time period was 49.6 times,and the climate change trend rate of cold air was decreased by 0.600 times per 10 years,while the decreasing tendency was not significant.Besides,annual mean strength of cold air in the whole region was 0.39,the climate change trend rate was decreased by 0.022 per 10 years,which had significant decrease tendency,the comprehensive average strength of the cold air in the whole region was 0.67,and climate change trend rate was decreased by 0.005 per 10 years,which did not show a significant reducing tendency.On a seasonal scale,the cold air frequency had significant reducing tendency in summer,while it had a non-significant reducing tendency in spring,a non-significant increase tendency autumn and winter.In addition,cold air strength had a significant weakening tendency in winter while the tendency was not obvious in other seasons.The comprehensive intensity of the strong cooling displayed a strengthening trend in spring and weakening trend in other seasons but none of them was significant.The decrease of the polar vortex area index and other factors in Europe region of Atlantic Ocean and the increase of the sea temperature index and other factors in tropical northern Atlantic Ocean increased mainly resulted in the declining of annual frequency of cold air.However,the enhancing of B index and other factors in Tibetan Plateau and the weakening of the SST dipole index and other factors of the tropical Indian Ocean were the main causes for the weakening of cold air strength.