江淮地区强降水分型及其环流演变

使用新建的强降水历史个例数据集、1981-2016年我国逐日降水量观测资料、2016年T639与ECMWF模式1~10 d的逐日降水量预报，采用经验正交函数展开（EOF）提炼出江淮地区强降水的典型模态，并运用场相似法对江淮地区强降水进行客观分型，分析强降水的环流演变；定量诊断型环流相似所得与实测环流和降水的对应关系。结果表明:江淮地区强降水可分为Q_Ⅰ，Q_Ⅱ和Q_Ⅲ 3种类型，其中，Q_Ⅰ型降水中心位于江淮中部，Q_Ⅱ型表现为降水北多南少，Q_Ⅲ型表现为降水中间少南北多的分布。强降水对应的前期至当日，各型降水对应在亚洲的中高纬度地区均有显著的环流异常，且环流演变存在明显不同；但各类型降水对应的系统移动速度缓慢，且到强降水发生日江淮地区处于西太平洋副热带高压西北侧低值系统的控制，有利于该地区强降水的发生。按环流相似依不同时效得到的强降水发生日环流与实际环流存在很好的相关。独立试验中，该文方法对25 mm降水的TS评分在各时效均高于模式预报，50 mm降水的TS评分在3 d以上时效的评分也均高于模式预报。

Pattern Classification of Heavy Rainfall in Jianghuai Region and Associated Circulations

Newly reconstructed dataset of regional historical heavy rain events, daily rainfall data of 2474 observational stations in China and NCEP/NCAR reanalysis data during 1981-2016, 1-10 d rainfall products of 2016 from ECMWF and T639 models are used to study heavy rainfall events in Jianghuai Region.Firstly, typical rain patterns are refined by empirical orthogonal function (EOF) based on 72 heavy rainfall cases. And then the classification of the regional heavy rainfall patterns for all heavy rainfall cases is done objectively through taking corresponding circulation patterns of basic rain patterns as targets with an analogue method.Furthermore, circulation characteristics of heavy rainfall patterns in Jianghuai Region are investigated. From the prophase of heavy rainfall at 500 hPa height fields, for Type Q_Ⅰ there is an enhancing large low vortex and it splits into two centers forming a circulation type of two troughs and one ridge, with marked anomalies but small amplitudes at low latitudes near Jianghuai Region. Both Type Q_Ⅱ and Type Q_Ⅲ is dominated by meridional circulation, but Type Q_Ⅱ is dominated by negative anomalies over mid-high latitudes of Asian, and then gradually one trough and one ridge develop, with the western Pacific subtropical high(WPSH) extending further westward at low latitudes. Type Q_Ⅲ is dominated by two ridges and one trough forms at mid-latitudes, with the WPSH weaker and unremarkable. However, synoptic systems of all three patterns move slowly, and Jianghuai Region is under the control of a relatively low system by the northwest side of WPSH, which is prevail to the heavy rainfall over this region. The jet stream locates to the north of Jianghuai Region with an anomalous divergence over the region at 200 hPa, but the strength of the jet stream is different for different patterns.Finally, the relationship between circulation patterns and related heavy rain are investigated. The circulation fields are estimated using height field analogue method with different leading time from 10 d to 0, and correlation coefficients between these parameters and the observation are considerable high, such as the height of 500 hPa, meridional wind component at 850 hPa, relative humidity at 700 hPa, and zonal wind at 200 hPa. Threat scores (TS) of the rainfall for days with daily rainfall more than 25 mm and 50 mm are also checked. TS in independent experiments of different lead time from 1 d to 10 d are higher than those from ECMWF and T639 models for events with daily rainfall more than 25 mm.