中国西北四省区四季变化时空特征

Temporal and Spatial Characteristics of Four Seasons in Four Provinces in Northwest of China

利用西北四省区(陕西、甘肃、宁夏、青海) 161个台站1981—2015年逐日平均气温资料和国家气候中心提供的逐月130项环流指数,采用统计学方法,对研究区域四季的开始日序与各季节持续时间进行了分析。结果表明:西北四省区整体春、夏季开始日序呈提前特征,秋、冬季开始日序呈延迟特征,其中春季变化幅度最大,冬季最小;冬、春季持续时间缩短,夏、秋季持续时间延长,其中夏季变化幅度最大,秋季最小;冬季持续时间随海拔升高而延长;西北四省区中部地区为四季开始日序与持续时间变化幅度大的区域。9月极涡面积影响着同期冬季的结束及来年春季的开始; 4月印度副高脊线位置与亚洲区极涡面积的状态决定了夏季的开始;夏季的持续时间与秋季的开始日序受两个区域海温之间的调整影响;秋季持续时间与冬季开始日序受10月东亚槽与西藏高压的影响。

The beginning date and duration of in Shaanxi,Gansu,Ningxia,Qinghai in Northwest China were analyzed by using the statistical method based on the daily mean temperature data from 161 stations and 130 monthly circulation indexes provided by the National Climate Center during 1981-2015.The results were as follows:The beginning date sequence showed an advanced trend for spring and summer.The beginning date sequence delayed for autumn and winter.The change amplitude of beginning date sequence was largest in spring,and lowest in winter.The duration of winter and spring shortened.The duration of summer and autumn extended.And the change amplitude of duration was largest in summer,and lowest in autumn.The winter duration increased with altitude.The central region of the study area in Northwest China had larger variations in the beginning date sequence and duration of four seasons.The ending of winter and beginning of spring in the next year were influenced by the pole vortex area in September.The beginning of summer was determined by the position of the Indian subtropical high ridge and the area of Asia polar vortex in April.The duration of summer and the beginning of autumn was affected by the adjustment of the sea temperature between the two regions.The duration of autumn and beginning of winter were affected by the position of east Asian trough and high pressure of Tibet in October.