研究山地突发性降雨过程的基本特征及其动力、热力引起的局地环流,对提高山地环境下突发性暴雨的预报准确性和及时性具有重要意义。本文选取绵阳地区两次山地突发性降雨事件,基于中国逐日降水快速融合实况分析产品(CMA Multi-source mer...研究山地突发性降雨过程的基本特征及其动力、热力引起的局地环流,对提高山地环境下突发性暴雨的预报准确性和及时性具有重要意义。本文选取绵阳地区两次山地突发性降雨事件,基于中国逐日降水快速融合实况分析产品(CMA Multi-source merged Precipitation Analysis System,CMPAS)、FY-2G卫星相当黑体亮温(Black Body Temperature,TBB)及欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasting,ECMWF)ERA5再分析资料,采用绕流、爬流和过山气流方程进行诊断分析和数值模拟试验。结果表明,两次突发性降雨均发生在西太平洋副热带高压控制的弱天气系统背景下,适宜的水汽条件、高温环境及冷暖空气交汇是暴雨触发的主要因素。山地阻挡作用促使过山气流产生绕流和爬流运动,在暴雨区形成上升运动和局地涡旋。在弱冷空气影响下,爬流运动占主导,爬流与绕流共同促进突发性暴雨的发生与发展;而在强冷空气影响下,二者对暴雨的促进作用减弱。暴雨区内绕流和爬流与降水强度耦合。降雨过程中,地面热源输入的消失导致降雨区附近地表热力扰动明显减弱,使盆地西部难以形成局地环流,进而削弱绕流和爬流,同时辐合区消失,导致数值模拟区域降水量明显减少,强降水中心消失。两次降雨过程中数值模拟试验结果均表明,相较于感热,潜热对降水起主要作用。展开更多
This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,t...This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,the maximum regionalaverage HRR and site-observed HRR,which exhibited sequential development over southern,middle,and northern key regions.These rainfall extremes occurred in an environment where a high-pressure barrier over North China prevented the intrusion of cold air masses from the north while a northward-moving typhoon remnant vortex and its associated low-level jet(LLJ)transported warm and moist airflow from the south.Two distinct echo evolution modes and convection initiation mechanisms are identified for the two types of extreme HRRs.The maximum regional-average HRR occurred when the LLJ arrived to the east of the key regions,while the maximum site-observed HRR occurred when the warmer vortex center influenced the regions.Taking the northern key region as a representation,at the time of the maximum regional-average HRR,slantwise ascent of the airflow along a warm-frontal-like boundary released energy related to symmetrical instability,resulting in stratiform rainfall with weak convective cores.The transport of locally initiated convection over the eastern plain region,where the atmospheric stratification was more potentially unstable,also significantly contributed.When the maximum site-observed HRR occurred,the terrain lifting of warm and moist southeast airflow led to intense convection over the mountain foothills.Overall,the passage of the warm-core typhoon remnant vortex and interaction with Taihang Mountains determined the timing and location of extreme HRRs across the key regions.展开更多
文摘研究山地突发性降雨过程的基本特征及其动力、热力引起的局地环流,对提高山地环境下突发性暴雨的预报准确性和及时性具有重要意义。本文选取绵阳地区两次山地突发性降雨事件,基于中国逐日降水快速融合实况分析产品(CMA Multi-source merged Precipitation Analysis System,CMPAS)、FY-2G卫星相当黑体亮温(Black Body Temperature,TBB)及欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasting,ECMWF)ERA5再分析资料,采用绕流、爬流和过山气流方程进行诊断分析和数值模拟试验。结果表明,两次突发性降雨均发生在西太平洋副热带高压控制的弱天气系统背景下,适宜的水汽条件、高温环境及冷暖空气交汇是暴雨触发的主要因素。山地阻挡作用促使过山气流产生绕流和爬流运动,在暴雨区形成上升运动和局地涡旋。在弱冷空气影响下,爬流运动占主导,爬流与绕流共同促进突发性暴雨的发生与发展;而在强冷空气影响下,二者对暴雨的促进作用减弱。暴雨区内绕流和爬流与降水强度耦合。降雨过程中,地面热源输入的消失导致降雨区附近地表热力扰动明显减弱,使盆地西部难以形成局地环流,进而削弱绕流和爬流,同时辐合区消失,导致数值模拟区域降水量明显减少,强降水中心消失。两次降雨过程中数值模拟试验结果均表明,相较于感热,潜热对降水起主要作用。
基金supported by the National Key R&D Program of China(2022YFC3003903)Natural Science Foundation of Beijing(Grant No.8222079)and of China(Grant No.42475014,U2442204)the Basic Research Fund of CAMS(2023Z001).
文摘This study investigates extreme rainfall episodes along the eastern foothills of the Taihang Mountains in North China from 30 July to 1 August 2023.It focuses on two types of extreme hourly rainfall rates(HRRs),i.e.,the maximum regionalaverage HRR and site-observed HRR,which exhibited sequential development over southern,middle,and northern key regions.These rainfall extremes occurred in an environment where a high-pressure barrier over North China prevented the intrusion of cold air masses from the north while a northward-moving typhoon remnant vortex and its associated low-level jet(LLJ)transported warm and moist airflow from the south.Two distinct echo evolution modes and convection initiation mechanisms are identified for the two types of extreme HRRs.The maximum regional-average HRR occurred when the LLJ arrived to the east of the key regions,while the maximum site-observed HRR occurred when the warmer vortex center influenced the regions.Taking the northern key region as a representation,at the time of the maximum regional-average HRR,slantwise ascent of the airflow along a warm-frontal-like boundary released energy related to symmetrical instability,resulting in stratiform rainfall with weak convective cores.The transport of locally initiated convection over the eastern plain region,where the atmospheric stratification was more potentially unstable,also significantly contributed.When the maximum site-observed HRR occurred,the terrain lifting of warm and moist southeast airflow led to intense convection over the mountain foothills.Overall,the passage of the warm-core typhoon remnant vortex and interaction with Taihang Mountains determined the timing and location of extreme HRRs across the key regions.
