东北地区5—9月降水特征和趋势分析

利用国家气象信息中心整编的1956—2008年站点逐日降水量、温度和NCEP/NCAR的月平均再分析资料,从逐年5—9月季节降水量和分级(痕量、微量、小雨、中雨、大雨和暴雨)降水事件两方面分析了东北地区的气候特征,并探讨了其可能原因。结果表明:5—9月份东北地区降水中心位于长白山脉的迎风坡,该区域同时是大雨和暴雨事件的多发区,这与地形和东亚夏季风气流北推有关;东北地区痕量降水事件东西方向呈"多—少—多"分布,其他级别的降水事件为西少东多;南北方向上,中雨以下量级为北多南少,大雨和暴雨事件则为北少南多;由于西风和南风气流水汽输送作用的减弱导致了1956—2008年东北地区5—9月降水量的线性递减;小雨及以下量级降水事件线性减少的趋势显著,但随着量级加大,各级别降水事件线性递减的趋势逐渐不明显,暴雨事件在1956—1976年、1976—1994年和1994—2008年三个时段内有明显的"减少—增多减少"的变化过程。

Characteristics and Trends of Rainfall Events in Northeast China from May to September During 1956-2008

The daily stational rainfall and temperature dataset from National Meteorological Information Center of China Meteorological Administration as well as the NCEP/NCAR monthly reanalysis data are used to analyze the characteristics and trends of climate rainfall events in Northeast China for the period 1956-2008. The center of precipitation is located in the windward direction of Changbai Mountains. The large and heavy rain events also happen in the same area frequently. This is in association with the terrain and the push of the northward flow of the East Asia summer monsoon. Secondly, the trace rain events are observed as more less more in the zonal direction, and the other rainfall events occur more in east than that of west. In the meridianal direction, more trace, light and small rainfall events occur in north whereas fewer large and heavy rain events in north. Thirdly, the decreasing of water vapor transport crossing the west and south boundary causes the decreasing of seasonal rainfall during May to September in Northeast China. Finally, the decreasing trends of trace, light and small rainfall events are significant. As the increasing of rainfall grades, the decreasing trends get less obviously. Decreasing increasing decreasing trends of heavy rain events are evidently shown in the periods 1956-1976, 1976-1994 and 1994-2008 respectively.