2017年广州“5·7”暖区特大暴雨的中尺度系统和可预报性
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摘要
2017年5月7日广州发生了特大暴雨,各家确定性业务预报模式均漏报了此次过程。本文利用常规观测资料和广州天气雷达资料对此次暖区特大暴雨过程的天气尺度背景、中尺度系统演变和可预报性进行了详细分析,同时通过分析ECMWF集合预报中成功预报出广州周边地区出现局地强降水与预报了弱降水的成员间的差异,探讨影响本次大暴雨发生的关键触发因子。结果表明:2017年"5·7"大暴雨的环境条件和动力强迫较弱,在弱风场环境下,冷高压后部东南风或偏南风回流,经过城市热岛区域,转为偏暖气流,与山坡下滑冷气流在山前一带形成的水平风场辐合,结合山前强水平温度梯度,共同触发了初生对流单体。其后,雷暴出流和边界层暖湿气流形成的辐合线又触发新生单体,并使已减弱的降水单体重新加强产生第二阶段强降水。前两个阶段的局地特大暴雨分别是由稳定少动的块状强回波单体发展到嵌有中涡旋的强单体和较长生命史的弱HP型超级单体造成的,第三阶段的大暴雨是由向南传播合并新生单体并随短波槽东移的带状回波造成;三个阶段成熟回波垂直结构上均呈低质心暖云降水的特点。由ECMWF集合预报成功预报出局地强降水与弱降水成员之间的差异可见,加强的温度梯度及地面风场辐合可能是本次局地强降水的重要触发因子。短期时效内数值模式难以做出暖区尤其是弱风场环境下暴雨以上降水预报,目前的监测和短时临近预警是主要手段。
Based on the conventional observation data and the Guangzhou Doppler weather radar data,this article analyzed the synoptic background,mesoscale systems and predictability of the torrential rain process which occurred in Guangzhou on 7 May 2017.By contrasting the members of ECMWF ensemble forecast which successfully forecasted the local heavy precipitation on 7 May 2017 with the failed member,key triggering factor affected this process was investigated.The results show that the ambient condition and dynamic forcing were weaker on 7 May 2017.In the context of weak wind field,a convergence line formed between the warm flow from the sea and the cold downslope wind in the front of mountain,combined with the intense temperature gradient,initially triggering the generation of convective storms.Subsequently,the outflow of the preexisting thunderstorms impacted the warm,moist flow at boundary layer,inducing new convergence lines continually.Therefore the weakened storm-cells enhanced again and aroused the second stage of heavy rainfall.The first stages of the local torrential rain on 7 May 2017 was induced by short-lived severe local storm with a meso-vortex evolved from the steady and strong blockshaped echo.The second stage of this torrential rain was caused by long-lived heavy precipitation(HPtype)supercell storm.However,the band echo merging from a mass of new-born convective cells and moving eastward with the short-wave trough was responsible for the third stage of this torrential rain.The radar echo had the low-quality core vertical structure and warm cloud precipitation character during all the three stages.It has turned out that more enhanced temperature gradient and surface wind convergence might be the important triggering factors for local severe precipitation.This finding is based on the member comparison of ECMWF ensemble forecast that successfully forecasted the local heavy and weak precipitation on 7 May 2017.Now,it is still difficult for numerical models to forecast the extremely heavy rains in short lead-time forecast under the condition of warm sector and,especially,the weak wind field.The main method for this is to enhance rainstorm disaster monitoring and early warning.
Based on the conventional observation data and the Guangzhou Doppler weather radar data,this article analyzed the synoptic background,mesoscale systems and predictability of the torrential rain process which occurred in Guangzhou on 7 May 2017.By contrasting the members of ECMWF ensemble forecast which successfully forecasted the local heavy precipitation on 7 May 2017 with the failed member,key triggering factor affected this process was investigated.The results show that the ambient condition and dynamic forcing were weaker on 7 May 2017.In the context of weak wind field,a convergence line formed between the warm flow from the sea and the cold downslope wind in the front of mountain,combined with the intense temperature gradient,initially triggering the generation of convective storms.Subsequently,the outflow of the preexisting thunderstorms impacted the warm,moist flow at boundary layer,inducing new convergence lines continually.Therefore the weakened storm-cells enhanced again and aroused the second stage of heavy rainfall.The first stages of the local torrential rain on 7 May 2017 was induced by short-lived severe local storm with a meso-vortex evolved from the steady and strong blockshaped echo.The second stage of this torrential rain was caused by long-lived heavy precipitation(HPtype)supercell storm.However,the band echo merging from a mass of new-born convective cells and moving eastward with the short-wave trough was responsible for the third stage of this torrential rain.The radar echo had the low-quality core vertical structure and warm cloud precipitation character during all the three stages.It has turned out that more enhanced temperature gradient and surface wind convergence might be the important triggering factors for local severe precipitation.This finding is based on the member comparison of ECMWF ensemble forecast that successfully forecasted the local heavy and weak precipitation on 7 May 2017.Now,it is still difficult for numerical models to forecast the extremely heavy rains in short lead-time forecast under the condition of warm sector and,especially,the weak wind field.The main method for this is to enhance rainstorm disaster monitoring and early warning.
引文
陈炯,郑永光,邓莲堂,2007.城市建筑物对城市边界层三维结构影响的数值模拟[J].北京大学学报(自然科学版),43(3):343-350.
陈茂钦,徐海明,2011.江淮锋面和华南暖区两次暴雨过程可预报性对比[J].南京信息工程大学学报:自然科学版,3(2):118-127.
陈涛,林建,张芳华,等,2017.“16·7”华北极端强降水过程对流尺度集合模拟试验不确定性分析[J].气象,43(5):513-527.
谌芸,孙军,徐珺,等,2012.北京721特大暴雨极端性分析及思考(一)观测分析及思考[J].气象,38(10):1255-1266.
丁治英,刘彩虹,沈新勇,2011.2005-2008年5、6月华南暖区暴雨与高、低空急流和南亚高压关系的统计分析[J].热带气象学报,27(3):307-316.
董全,代刊,陶亦为,等,2017.基于ECMWF集合预报的极端天气预报产品应用和检验[J].气象,43(9):1095-1109.
董全,金荣花,代刊,等,2016.ECMWF集合预报和确定性预报对淮河流域暴雨预报的对比分析[J].气象,42(9):1146-1153.
杜青文,任荣彩,康锡言,1999.“96.8”河北特大暴雨地面中尺度系统分析[J].气象,25(7):25-28.
傅佩玲,胡东明,张羽,等,2018.2017年5月7日广州特大暴雨微物理特征及其触发维持机制分析[J].气象,44(4):500-510.
高安宁,李生艳,陈见,等,2009.弱环境风场条件下华南西部大范围暴雨特征分析[J].热带气象学报,22(增刊):9-17.
何立富,陈涛,孔期,2016.华南暖区暴雨研究进展[J].应用气象学报,27(5):559-569.
黄士松,1986.华南前汛期暴雨[M].广州:广东科技出版社:94-95.
孔凡超,赵庆海,李江波,2016.2013年7月冀中特大暴雨的中尺度系统特征和环境条件分析[J].气象,42(5):578-588.
林良勋,冯业荣,黄忠,等,2006.广东省天气预报技术手册[M].北京:气象出版社:120-122.
刘琳,陈静,程龙,等,2013.基于集合预报的中国极端强降水预报方法研究[J].气象学报,71(5):853-866.
陆汉城,杨国祥,2004.中尺度天气原理和预报:第二版[M].北京:气象出版社:53-54.
孙继松,2014a.从天气动力学角度看云物理过程在降水预报中的作用[J].气象,40(1):1-6.
孙继松,2014b.城市精细天气预报的理论与技术研究进展[J].气象科技进展,4(1):15-21.
孙继松,雷蕾,于波,等,2015.近10年北京地区极端暴雨事件的基本特征[J].气象学报,73(4):609-623.
孙继松,陶祖钰,2012.强对流天气分析与预报中的若干基本问题[J].气象,38(2):164-173.
孙继松,杨波,2008.地形与城市环流共同作用下的β中尺度暴雨[J].大气科学,32(6):1352-1364.
孙军,谌芸,杨舒楠,等,2012.北京721特大暴雨极端性分析及思考(二)极端性降水成因初探及思考[J].气象,38(10):1267-1277.
田付友,郑永光,张小玲,等,2018.2017年5月7日广州极端强降水对流系统结构触发和维持机制[J].气象,44(4):469-484.
王东海,杜钧,柳崇健,2011.正确认识和对待天气气候预报的不确定性[J].气象,37(4):385-391.
王淑莉,康红文,谷湘潜,等,2015.北京7·21暴雨暖区中尺度对流系统的数值模拟[J].气象,41(5):544-553.
王晓芳,赖安伟,王志斌,2014.一个长生命期准静止中尺度对流系统的观测特征及其持续的环境条件[J].大气科学,38(3):421-437.
韦统健,1994.华南前汛期暖区暴雨流场结构的特征[J].热带气象学报,10(1):37-46.
伍志方,曾沁,吴乃庚,等,2011.广州“5.7”高空槽后和“5.14”槽前大暴雨过程对比分析[J].气象,37(7):838-846.
夏茹娣,赵思雄,孙建华,2006.一类华南锋前暖区暴雨β中尺度系统环境特征的分析研究[J].大气科学,30(5):988-1008.
徐珺,杨舒楠,孙军,等,2014.北方一次暖区大暴雨强降水成因探讨[J].气象,40(12):1455-1463.
薛纪善,1999.1994年华南夏季特大暴雨研究[M].北京:气象出版社:106-124.
叶朗明,苗峻峰,2014.华南一次典型回流暖区暴雨过程的中尺度分析[J].暴雨灾害,33(4):342-350.
俞小鼎,2012.2012年7月21日北京特大暴雨成因分析[J].气象,38(11):1313-1329.
袁月,李晓莉,陈静,等,2016.GRAPES区域集合预报系统模式不确定性的随机扰动技术研究[J].气象,42(10):1161-1175.
张晓惠,倪允琪,2009.华南前汛期锋面对流系统与暖区对流系统的个例分析与对比研究[J].气象学报,67(1):108-121.
张晓美,蒙伟光,张艳霞,等,2009.华南暖区暴雨中尺度对流系统的分析[J].热带气象学报,25(5):551-560.
赵琳娜,刘琳,刘莹,等,2015.观测降水概率不确定性对集合预报概率Brier技巧评分结果的分析[J].气象,41(6):685-694.
赵玉春,李泽椿,肖子牛,2008.华南锋面与暖区暴雨个例对比分析[J].气象科技,36(1):47-54.
郑永光,陶祖钰,俞小鼎,2017.强对流天气预报的一些基本问题[J].气象,43(6):641-652.
周秀骥,薛纪善,陶祖钰,等,2003.98华南暴雨科学试验研究[M].北京:气象出版社:370.
Baik J J,Kim Y H,Chun H Y,2001.Dry and moist convection forced by an urban heat island[J].J Appl Meteor,40(8):1462-1475.
Tian Fuyou,Zheng Yongguang,Zhang Tao,et al,2015.Statistical characteristics of environmental parameters for warm season short-duration heavy rainfall over central and eastern China[J].J Meteor Res,29(3):370-384.
陈茂钦,徐海明,2011.江淮锋面和华南暖区两次暴雨过程可预报性对比[J].南京信息工程大学学报:自然科学版,3(2):118-127.
陈涛,林建,张芳华,等,2017.“16·7”华北极端强降水过程对流尺度集合模拟试验不确定性分析[J].气象,43(5):513-527.
谌芸,孙军,徐珺,等,2012.北京721特大暴雨极端性分析及思考(一)观测分析及思考[J].气象,38(10):1255-1266.
丁治英,刘彩虹,沈新勇,2011.2005-2008年5、6月华南暖区暴雨与高、低空急流和南亚高压关系的统计分析[J].热带气象学报,27(3):307-316.
董全,代刊,陶亦为,等,2017.基于ECMWF集合预报的极端天气预报产品应用和检验[J].气象,43(9):1095-1109.
董全,金荣花,代刊,等,2016.ECMWF集合预报和确定性预报对淮河流域暴雨预报的对比分析[J].气象,42(9):1146-1153.
杜青文,任荣彩,康锡言,1999.“96.8”河北特大暴雨地面中尺度系统分析[J].气象,25(7):25-28.
傅佩玲,胡东明,张羽,等,2018.2017年5月7日广州特大暴雨微物理特征及其触发维持机制分析[J].气象,44(4):500-510.
高安宁,李生艳,陈见,等,2009.弱环境风场条件下华南西部大范围暴雨特征分析[J].热带气象学报,22(增刊):9-17.
何立富,陈涛,孔期,2016.华南暖区暴雨研究进展[J].应用气象学报,27(5):559-569.
黄士松,1986.华南前汛期暴雨[M].广州:广东科技出版社:94-95.
孔凡超,赵庆海,李江波,2016.2013年7月冀中特大暴雨的中尺度系统特征和环境条件分析[J].气象,42(5):578-588.
林良勋,冯业荣,黄忠,等,2006.广东省天气预报技术手册[M].北京:气象出版社:120-122.
刘琳,陈静,程龙,等,2013.基于集合预报的中国极端强降水预报方法研究[J].气象学报,71(5):853-866.
陆汉城,杨国祥,2004.中尺度天气原理和预报:第二版[M].北京:气象出版社:53-54.
孙继松,2014a.从天气动力学角度看云物理过程在降水预报中的作用[J].气象,40(1):1-6.
孙继松,2014b.城市精细天气预报的理论与技术研究进展[J].气象科技进展,4(1):15-21.
孙继松,雷蕾,于波,等,2015.近10年北京地区极端暴雨事件的基本特征[J].气象学报,73(4):609-623.
孙继松,陶祖钰,2012.强对流天气分析与预报中的若干基本问题[J].气象,38(2):164-173.
孙继松,杨波,2008.地形与城市环流共同作用下的β中尺度暴雨[J].大气科学,32(6):1352-1364.
孙军,谌芸,杨舒楠,等,2012.北京721特大暴雨极端性分析及思考(二)极端性降水成因初探及思考[J].气象,38(10):1267-1277.
田付友,郑永光,张小玲,等,2018.2017年5月7日广州极端强降水对流系统结构触发和维持机制[J].气象,44(4):469-484.
王东海,杜钧,柳崇健,2011.正确认识和对待天气气候预报的不确定性[J].气象,37(4):385-391.
王淑莉,康红文,谷湘潜,等,2015.北京7·21暴雨暖区中尺度对流系统的数值模拟[J].气象,41(5):544-553.
王晓芳,赖安伟,王志斌,2014.一个长生命期准静止中尺度对流系统的观测特征及其持续的环境条件[J].大气科学,38(3):421-437.
韦统健,1994.华南前汛期暖区暴雨流场结构的特征[J].热带气象学报,10(1):37-46.
伍志方,曾沁,吴乃庚,等,2011.广州“5.7”高空槽后和“5.14”槽前大暴雨过程对比分析[J].气象,37(7):838-846.
夏茹娣,赵思雄,孙建华,2006.一类华南锋前暖区暴雨β中尺度系统环境特征的分析研究[J].大气科学,30(5):988-1008.
徐珺,杨舒楠,孙军,等,2014.北方一次暖区大暴雨强降水成因探讨[J].气象,40(12):1455-1463.
薛纪善,1999.1994年华南夏季特大暴雨研究[M].北京:气象出版社:106-124.
叶朗明,苗峻峰,2014.华南一次典型回流暖区暴雨过程的中尺度分析[J].暴雨灾害,33(4):342-350.
俞小鼎,2012.2012年7月21日北京特大暴雨成因分析[J].气象,38(11):1313-1329.
袁月,李晓莉,陈静,等,2016.GRAPES区域集合预报系统模式不确定性的随机扰动技术研究[J].气象,42(10):1161-1175.
张晓惠,倪允琪,2009.华南前汛期锋面对流系统与暖区对流系统的个例分析与对比研究[J].气象学报,67(1):108-121.
张晓美,蒙伟光,张艳霞,等,2009.华南暖区暴雨中尺度对流系统的分析[J].热带气象学报,25(5):551-560.
赵琳娜,刘琳,刘莹,等,2015.观测降水概率不确定性对集合预报概率Brier技巧评分结果的分析[J].气象,41(6):685-694.
赵玉春,李泽椿,肖子牛,2008.华南锋面与暖区暴雨个例对比分析[J].气象科技,36(1):47-54.
郑永光,陶祖钰,俞小鼎,2017.强对流天气预报的一些基本问题[J].气象,43(6):641-652.
周秀骥,薛纪善,陶祖钰,等,2003.98华南暴雨科学试验研究[M].北京:气象出版社:370.
Baik J J,Kim Y H,Chun H Y,2001.Dry and moist convection forced by an urban heat island[J].J Appl Meteor,40(8):1462-1475.
Tian Fuyou,Zheng Yongguang,Zhang Tao,et al,2015.Statistical characteristics of environmental parameters for warm season short-duration heavy rainfall over central and eastern China[J].J Meteor Res,29(3):370-384.