甘肃陇南市短时强降水时空分布特征及中尺度分析

Spatial-temporal distribution characteristics and mesoscale analysis of short-time heavy precipitation in Longnan of Gansu Province

利用1960—2019年陇南市9个国家气象站和2008—2019年逐年建成的400个区域气象站4—9月逐时降水资料,同期NCEP FNL 1°×1°再分析资料和MICAPS资料,对陇南市短时强降水时空分布及中尺度特征进行分析。结果表明:(1)陇南市短时强降水发生频次从西北向东南明显增加,雨强大于50 mm·h^(-1)的短时强降水出现在陇南市东部的成县、徽县和康县。短时强降水与暴雨发生频次东南部偏多,另外陇南市西北山地局部地区短时强降水发生频次较多。(2)1960年以来,陇南市短时强降水发生站次呈缓慢增加趋势,月际变化呈单峰型,8月最多,占短时强降水总站次的37.5%;旬变化呈双峰型,分别出现在7月上旬和8月上旬,且7月下旬至8月中旬最多,占47.2%;日变化具有夜间明显多于白天的特征,存在多个峰值,从15:00开始短时强降水明显增加,集中出现在19:00—23:00,23:00为日峰值,占9.4%。(3)陇南市短时强降水和暴雨有密切联系,对暴雨的贡献率达53.4%。陇南市短时强降水中尺度概念模型主要有低涡切变型、西北气流低槽东移型、副高外围西南气流型。

Based on the hourly precipitation data from April to September during 1960-2019 at 9 national meteorological stations and 400 regional meteorological stations built year by year in Longnan of Gansu Province from 2008 to 2019,NCEP FNL 1°×1°reanalysis data and MICAPS data,the spatial-temporal distribution and mesoscale characteristics of short-time heavy precipitation in Longnan of Gansu Province were analyzed.The results are as follows:(1)The occurrence frequency of short-time heavy precipitation in Longnan became more from the northwest to the southeast,with two relatively concentrated areas.The short-time heavy precipitation with rainfall intensity greater than 50 mm·h^(-1) occurred in Cheng county,Hui county and Kang county in the east of Longnan.The occurrence frequencies of short-time heavy precipitation and rainstorm were more in the southeast of Longnan,and for short-time heavy precipitation it was also relatively high in the mountainous areas in the northwest.(2)Since 1960,the stations occurring short-time heavy precipitation in Longnan increased slowly.The monthly variation showed a single-peak type,with the maximum in August and accounting for 37.5%of the total stations occurring short-time heavy precipitation.The ten-day variation presented a double-peak type,with two peaks in early July and early August,respectively.The stations occurring short-time heavy precipitation was the most from late July to mid-August,accounting for 47.2%of the total stations.Diurnal variation showed that there was more short-time heavy precipitation at night than in the day,there were multiple peaks.The stations occurring short-time heavy precipitation increased significantly since 15:00 BST.The diurnal peaks of short-time heavy precipitation occurred at 23:00 BST,accounting for 9.4%of the total stations.(3)The short-time heavy precipitation in Longnan was closely linked to rainstorms.The mesoscale concept modes of short-time heavy precipitation in Longnan mainly showed three types,including low vortex shear,northwest air flow following the trough moving eastward and the southwest air flow beside the sub-tropical high.