陆面热力异常与东亚夏季中纬度气旋年代际变化的联系

基于欧洲中期预报中心的再分析数据ERA-interim,利用统计学方法分析了1979—2013年期间东亚中纬度地区气旋生成频率和陆面热力异常的年代际变化及两者的可能联系。结果表明,东亚中纬度地区存在气旋活动频繁的气旋源地,该地区的温带气旋生成频率具有明显的年代际变化,1990年之前气旋生成频率偏多,1990s至今偏少,而且东亚中纬度地区陆面热力异常的变化有明显的年代际增暖信号;进一步的分析发现,东亚夏季中纬度气旋活动的年代际变化与陆面异常异常之间存在密切的联系,东亚中纬度地区陆面年代际增暖,是引起温度气旋活动年代际减弱的一个重要原因。由于陆面增暖的非均匀性,在50°N以北存在一个影响中纬度气旋生成频率的关键区,关键区陆面的年代际异常增暖,导致气旋源地温度经向梯度减弱,大气斜压性随之减弱,从而使得气旋生成频率年代际减少。

Relationship between land surface thermal anomaly and the interdecadal variation of extra-tropical cyclone activity during summer over East Asia

Based on the ERA-interim reanalysis data from 1979 to 2013, the interdecadal variations of the extra-tropical cyclones and land surface thermal anomaly and their possible relationship are investigated with statistical methods. Results show that there exists a distinct cyclogenesis area in the mid-latitude region of East Asia, and the frequency of cyclogenesis over this area exhibits significant interdecadal changes. Before 1990, the frequency of cyclogenesis was relatively high; however, from the 1990s to the present, it is relatively weak. Meanwhile, the land surface thermal anomaly shows a decadal increasing trend. Further analysis suggests that there is a close linkage between the decadal warming of the land surface in the mid-latitude of East Asia and the decadal weakening of the cyclone activity. Due to the heterogeneity of the land surface warming, it is a key region in the north of that has a significant effect on the cyclone activity over the cyclogenesis area. The decadal warming of the key region tends to decrease the meridional gradient of the surface soil temperature over the cyclongenesis source region, leading to the weakening atmospheric baroclinicity, and the decreasing frequency of the cyclogenesis.