doi:  10.3878/j.issn.1006-9895.1901.18239

Comparative Analyses of Mechanisms and Energy Budgets of Local Extreme Rainfall Events Caused by Remnant Clouds ofTwo Typhoons with Similar Tracks
摘要点击 311  全文点击 218  投稿时间:2018-10-17  
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基金:  中国气象局关键技术发展专项YBGJXM 2018 2017C03035国家自然科学基金项目41575042,中国气象局关键技术发展专项YBGJXM (2018) 1B-06,浙江省科技重大项目2017C03035
中文关键词:  台风  局地特大暴雨  辐散动能  旋转动能
英文关键词:  Typhoon  Local extreme rain  Divergent kinetic energy  Rotational kinetic energy
潘劲松PAN Jinsong浙江省气象台,杭州310017
周玲丽ZHOU Lingli浙江省气象台,杭州310017
陆玮LU Wei浙江省气象台,杭州310017
罗玲LUO Ling浙江省气象台,杭州310017
翟国庆ZHAI Guoqing浙江大学地球科学系,杭州310027
Citation:PAN Jinsong,ZHOU Lingli,LU Wei,LUO Ling,ZHAI Guoqing.2019.Comparative Analyses of Mechanisms and Energy Budgets of Local Extreme Rainfall Events Caused by Remnant Clouds ofTwo Typhoons with Similar Tracks[J].Chinese Journal of Atmospheric Sciences (in Chinese),43(6):1399-1412,doi:10.3878/j.issn.1006-9895.1901.18239.
      本文利用ERA-Interim 0.5°×0.5°再分析资料、自动站小时和分钟加密资料、风云2G(FY-2G)卫星红外云图及多普勒雷达和风廓线雷达资料对2015年路径高度相似的“苏迪罗”和“杜鹃”台风在浙江沿海引发的局地特大暴雨进行对比分析。这两次降水过程都是在台风减弱为热带低压甚至残压并深入内陆远离浙江沿海后发生的。结果表明,“苏迪罗”降水过程是由低层强东南和偏南急流长时间辐合加上有利地形共同作用导致的;经向环流背景下来自季风持续的水汽输送有利于“苏迪罗”维持较长的生命史和稳定的降水。“杜鹃”残压特大暴雨的触发系统则是高纬地面冷高压底部的东东北出流南下与“杜鹃”北象限的东东南风交汇形成的中尺度倒槽;纬向环流和强盛副热带高压造成的弱引导气流及夏季风南撤和低涡卷挟造成的水汽通道断裂是“杜鹃”登陆后快速减弱为残压和降水维持时间较短的原因。两次台风降水过程中均无外部动能输送和来自有效位能的动能转换。动能收支的主要影响因子为中低层局地次网格运动间的能量转换、旋转风和散度风效应及下垫面的摩擦耗散。所以,虽然“杜鹃”的对流有效位能很小,但仍可造成强对流和特大暴雨。此外,降水过程中释放的凝结潜热造成的局地非绝热加热使气柱中显热能大量累积,促使地面中小尺度涡旋和倒槽不断加深,造成降水的增幅。
      Using 0.5°×0.5° ERA-Interim analysis data from the European Centre for Medium-Range Weather Forecasts, hourly and minutely observational data from Automatic Weather Stations (AWS), Doppler radar and wind profile radar, as well as infrared cloud images from the Fengyun 2G Satellite (FY-2G), we investigated two local torrential rain events in coastal Zhejiang Province caused by two typhoons with similar tracks, Soudelor and Dujuan, 2015. Both rain events were generated after the typhoons had weakened to tropical depression or remnants and travelled far from Zhejiang. It was found that the rain event associated with Soudelor was triggered by long-duration convergence of a strong low-level southeast jet and a south jet as well as topography. Meridional circulation with persistent water vapor transfer by summer monsoon provided a favorable background for the long-lasting life cycle of Soudelor and its precipitation. In contrast, the rain brought about by remnants of Dujuan was produced by a mesoscale inverted trough, comprised of the east-northeast boundary layer flow out of the cold high in the high latitudes and the east-southeast wind in the north quadrant of Dujuan. Zonal circulation, weak steering currents under a powerful western pacific subtropical high, water vapor transport cut off by monsoonal retreat, and vortex entrainment were reasons for the rapid decay of Dujuan and reduced duration of rain compared with Soudelor. There was no external transfer or convective available potential energy (CAPE) conversion to kinetic energy for both rain events. Rotational divergent wind effects and energy transfer between resolvable and unresolvable scale motions, as well as frictional processes in the lower and middle levels, were main-impact factors in the kinetic energy budgets of these two rain events. As a result, convective forcing and heavy rain occurred despite the small CAPE of Dujuan. Diabatic heating associated with condensational latent heat released by local precipitation massively increased the sensible heat energy in the air column, and consequently, potentially promoted meso- and micro-scale vortices and an inverted trough. As a result, the rain events were intensified and sustained.
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