河西走廊春末夏初降水的空间异常分布及年代际变化

利用河西走廊19个气象代表站建站至2002年5～6月降水量资料, 分析了河西走廊春末夏初干旱的基本气候特征; 在利用EOF和REOF方法进行降水空间异常变化分析和气候分区的基础上,讨论了第一时间系数(PC1)及各区代表站降水量的年代际变化规律. 结果表明, 河西走廊春末夏初降水量在第一空间尺度上为全区一致; 在第二空间尺度上可分为3个气候区; 在第三空间尺度上可分为5个自然气候区. 1980年代为近50 a来降水最多的10 a, 1990年代有所减少, 20世纪末至21世纪初有明显增加. 前期冬季欧亚径向环流加强, 亚洲区极涡面积扩大、强度加强, 冷空气活动频繁, 将有利于次年春末夏初河西走廊降水偏多. 欧洲青藏高原华北西太平洋的波列, 特别是东亚大槽的填塞和青藏高原低值系统频繁活动, 造成了500 hPa高空场上"东高西低"的典型多雨流型.

Abnormal Space Distribution of Precipitation in Hexi Corridor in the Late Spring and Early Summer and Its Inter-Decadal Variability

Using EOF and REOF methods, precipitation data from May to July from 19 representative stations in Hexi corridor up to 2002 were analyzed to reveal the drought characteristics and abnormal space distribution of precipitation in Hexi corridor from the late spring to the early summer. Basing on climate sectoring, inter-decadal variability of precipitation is discussed for the first time series and every representative station, and the coefficient between the first time series and the prophase circulation factor is calculated on the 500 hPa geopotential height in northern hemisphere. It is found that precipitation in Hexi corridor in the late spring and early summer has a better coherence in the first space. There are three nature sectors in the second space. There are five nature sectors in the third space. Precipitation in the 1980s is the maximum of the recent 5 decades. Precipitation in the 1990s decreased, and from the end of the 20th century to the beginning of the 21st century precipitation has an obvious increasing trend in China. If the early Eurasian meridional circulation strengthens in winter, then polar vortex area will enlarge, polar vortex intension will strengthen and cold air will be more active, propitious to precipitation in Hexi corridor in the late spring and early summer. Wave train in Europe, Tibetan Plateau, North China and West Pacific results in a typical pluvial stream with high in east and low in west on the 500 hPa geopotential height, especially the ram and move of East Asian trough. Foreshadow model of precipitation in the late spring and early summer in representative station has a fitting percent of about 72.