甘肃北部短时强降水中尺度特征及物理量配置

Mesoscale characteristics and physical quantity allocation of short-time heavy rainfall in northern Gansu Province

利用甘肃北部27个国家级自动气象站及635个区域气象站降水资料,结合常规高空、地面和欧洲中期天气预报中心(ECMWF)再分析物理量场资料,选取了2016—2019年5—9月104个典型短时强降水个例,对甘肃北部短时强降水天气发生发展的环境条件进行了中尺度综合分析,揭示了区域内短时强降水的一些特征和规律。结果表明:(1)甘肃北部短时强降水集中出现在6—8月,短时强降水的强度多为10~20 mm。(2)甘肃北部短时强降水天气的典型特征,分为副高边缘型、低压槽型、西北气流型和河套阻高型4种流型。(3)通过分析不同天气形势、不同类别、不同物理量参数间的联系与区别,总结出各类短时强降水天气的环流特征和物理量要素指标和阈值。(4)地面辐合线(冷锋)是甘肃北部触发强对流天气的关键系统,地面辐合线(冷锋)的分析对短时临近预报至关重要。(5)低空偏南风急流(显著流线)在110°E左右北上及在37°N左右产生辐合是判断甘肃北部能否产生短时强降水的重要依据。并对2020年短时强降水预报效果进行检验,预报准确率达63.6%,说明建立的短时强降水预报指标预报能力较强,为提高短时强降水预报预警能力提供了一种新途径。

From the precipitation data of 27 national automatic weather stations and 635 regional weather stations in northern Gansu Province of China,combined with the conventional air,ground,and ECMWF reanalysis data,104 cases of typical short-time heavy rainfall from May to September during 2016—2019 were selected.In this paper,mesoscale comprehensive analysis of environmental conditions for the occurrence and development of short-time heavy rainfall in northern Gansu Province was performed,and some characteristics and laws of short-time heavy rainfall in this region were revealed.The results show the following:(1)The short-time heavy rainfall in northern Gansu Province primarily occurs from June to August,and the intensity of short-time heavy rainfall is mostly 10-20 mm.(2)The typical characteristics of short-time heavy rainfall weather in northern Gansu Province can be divided into four flow types:subtropical high marginal type,low-pressure trough type,northwest airflow type,and high flow resistance type.(3)The relation and difference between different weather conditions,flow types,and physical parameters are discussed.The circulation characteristics and physical factors indexes and thresholds of various short-time heavy rainfall weather are summarized.(4)The surface convergence line(cold front)is the key system triggering severe convective weather in northern Gansu Province,and the analysis of the surface convergence line(cold front)is critical for short-time near rainfall forecast.(5)Low-level southerly jet(significant streamline)convergence at 110°E and 37°N is an important basis for judging whether short-time heavy rainfall can occur in northern Gansu Province.The prediction accuracy of short-time heavy rainfall in 2020 is 63.6%,indicating that the established short-time heavy rainfall forecast index has a strong capability,providing a new way to improve the short-time heavy rainfall forecast and early warning ability.