淮河流域持续性强降水的重要前期信号

The Precursor Signals of Persistent and Strong Precipitation Along the Huaihe River Valley

利用淮河流域4省20—20时逐日降水量资料,NCEP再分析500 hPa高度场资料,对1961—2006年淮河流域持续性强降水过程进行界定,并分析了持续性强降水前期、过程中的中高纬度阻塞高压发展变化。结果发现:平均而言6月29日至7月25日为淮河流域降水最集中的时段,持续性强降水过程大多发生在6月中旬到7月中旬;淮河流域持续性强降水的重要前期信号为:降水开始前一阶段乌拉尔山附近均有明显的阻塞形势出现,双阻形势居多,而持续性强降水期间乌拉尔山附近阻高减弱,贝加尔湖以北到鄂霍茨克海附近的阻高偏强,单阻居多,持续性强降水大多开始于乌拉尔山附近阻高指数锐减后的2～5天;持续性强降水年份乌拉尔山附近阻塞高压大多存在15～30天左右的主要振荡周期,绝大多数年份乌拉尔山附近阻塞高压和180°E附近阻高在强降水发生之前开始出现西退的现象。淮河流域持续性强降水过程的环流特征对把握淮河流域的强降水特点及预报前兆信号有实际意义,为淮河流域持续性强降水预报提供了依据,具有重要的应用价值。

By analyzing the daily precipitation data of four provinces along the Huaihe River Valley,and the reanalysis of NCEP 500 hPa height field,the persistent and strong precipitation process（PSPP） along the Huaihe River Valley between 1961 and 2006 was defined.The development and change of the blocking high at high latitudes prior to and during the PSPP were analyzed as well.The research results have brought the conclusion that on average,from June 29 to July 25,the Huaihe River Valley had the highest precipitation.The PSPP happened mostly between mid-June to mid-July.Before the PSPP starting,obvious blocking high pattern was found near the Urals,in which double blockings dominated.Whereas during the PSPP,the blocking high near the Urals weakened and that at the north and east of the Lake Baikal became strong,in which a single blocking dominated.The PSPP mostly happened 2 to 5 days after the sharp decrease of the blocking high index.During the years of PSPP,the blocking high near the Urals had an oscillation cycle of 15 to 30 days.In most of the years,the blocking high near the Urals and 180°E moved to the west before the PSPP started.The results in this article are helpful in mastering the characteristics of the strong precipitation along the Huaihe River Valley and precursor signal,and lay the basis for the forecasting of the persistent and strong precipitation along the Huaihe River Valley.