江淮区域梅雨的划分指标研究

为便于江淮区域的梅雨划定, 更好地开展区域梅雨短期气候预测业务, 本文从区域角度出发, 在明确区域梅雨概念的基础上, 选取江淮区域梅汛期降水变率一致的36个代表站点, 根据梅雨的大范围持续性时空分布特征, 采用连续5个滑动候满足候内雨日≥4的站点覆盖率指标, 并结合西太平洋副高脊线位置, 提出了江淮区域梅雨入、出梅的确定方法。基于所提出的区域梅雨划分指标, 进一步分析了江淮区域梅雨特征量的气候特征, 并与已有的长江中下游梅雨特征量进行了比较。结果表明, 本文定义的区域梅雨指标既考虑了梅雨系统大范围持续性降水的天气现象, 又可反映典型梅雨系统的高低层环流配置及梅雨的降水条件, 能较好地描述梅雨的区域气候特征。区域梅雨指标反映的入、 出梅日期的气候特征、 长期变化趋势及异常梅雨等方面与已有长江中下游梅雨特征量基本一致, 但本文的区域梅雨入、 出梅与大气环流季节性调整具有更好的一致性, 且采用江淮区域空间分布均匀的36个站点来描述区域梅雨更具代表性。

A Study of Determination Index of Regional Meiyu over the Yangtze-Huaihe Basin

In order to determine the Yangtze-Huaihe regional Meiyu and develop its relating short-term climate pre-diction operation,based on the regional Meiyu concept,a new index of determining Yangtze-Huaihe regional Meiyu is firstly put forward according to regional Meiyu's large-scale durative characteristics of both temporal and spatial distributions after 36 typical stations over the Yangtze-Huaihe region are selected.The percentage of station cover-age satisfying rainfall days≥4 for 5 consecutive running pentads is adopted combining with the location of the west-em Pacific subtropical high ridge in the definition of the Meiyu criteria.The climatic features of regional Meiyu are then analyzed on the basis of determined regional Meiyu.And those features are compared with Meiyu over the mid-dle and lower reaches of the Yangtze River.Results indicate that the new index can well describe climatic eharacter-istics of regional Meiyu on both large-scale continuous rainfall phenomenon and high-low levels circulation configura-tion of Meiyu system.Meanwhile,comparison of different regional Meiyu indexes suggests that the climate feature,long-term change,and abnormal Meiyu years reflected by the new index are in common with the existing Meiyu data for the middle and lower reaches of the Yangtze River.However,the new index defined in this paper is superior to the Yangtze River Meiyu index defined by the observations at five stations in some respects such as coherence of cir-culation adjustment,representation of regional Meiyu depicted by 36 observational stations with uniform spatial dis-tribution,and so on.