两次华北冷涡降水成因及预报偏差对比分析  

Comparative Study of the Cause of Rainfall and Its Forecast Biases of Two Cold Vortex Rainfall Events in North China

作　　者：符娇兰[1] 陈双 沈晓琳 张夕迪 权婉晴 FU Jiaolan;CHEN Shuang;SHEN Xiaolin;ZHANG Xidi;QUAN Wanqing(National Meteorological Centre,Beijing 100081)

机构地区：[1]国家气象中心

出　　处：《气象》2019年第5期606-620,共15页Meteorological Monthly

基　　金：国家重点研发计划(2018YFC1507703);中国气象局预报员专项(CMAYBY2018-089);国家科技支撑计划(2015BAC03B02)共同资助

摘　　要：利用多种常规及非常规观测资料、美国国家环境预报中心全球模式业务系统分析资料(NCEP/FNL)以及三家全球确定性模式产品对2017年两次华北冷涡降水过程成因及模式预报偏差进行了对比分析。结果表明;个例1(6月22日)降水回波为层-积混合型,对流发展高度低,小时雨强小,先后经历了持续的稳定降水和弱对流降水两个阶段;个例2(7月6日)降水以积云状对流回波为主,对流发展高度高,短历时强降水特点明显。二者对应的环境场差异较大,前者冷涡处在成熟期,副热带高压位置偏南,前期暖区对流冷池降温明显,对流能量及水汽条件一般;后者冷涡为发展期,副热带高压位置偏北,中低纬相互作用明显,水汽与能量充沛。两次过程北京均出现了暴雨及以上量级降水,对应的中尺度对流系统(MCS)特征、对流触发机制以及对流不稳定能量重建过程存在明显差异。前者为层状云中发展的γ中尺度MCS,边界层偏东风增强为MCS提供了触发机制,中低层偏东风暖湿输送以及对流层高层干冷平流有利于对流不稳定能量重建;后者为组织化的β中尺度MCS,列车效应明显,偏南低空急流及其气旋式切变配合地形为MCS发展提供了抬升条件,对流不稳定能量建立与中低层偏南低空急流强暖湿输送有关。各家数值模式对不同类型冷涡降水的预报偏差特征一致,即对冷涡成熟期的降水,因对动力条件预报过强导致空报降水;而对冷涡发展期的降水,由于对槽前暖区辐合及其对流性降水预报不足导致强降水出现漏报。By using the conventional observation,and the radiosonde,satellite,radar,wind profile,NCEP-FNL analysis data as well as the data of three deterministic global forecast systems,causes of rainfall and forecast biases of two cold vortex rainfall events in 2017 over North China are comparatively studied.The results show that the event that occurred on 22 June 2017 is characterized by persistent and steady rainfall with weak rainfall intensity and lower convective height.The rainfall echo is of convectivestratiform mixed type.However,the rainfall on 6 July is short-time severe rainfall and the height of convective echo top is very high.The background conditions are quite different between these two cases.For the 22 June event,cold vortex is at its mature stage and subtropical high is far south.Moreover,a warm section convection occurred on the previous day,and its cold pool is quite strong,leading to the release of convective energy,thus the convective energy and water vapor are normal for the first case.Comparatively,for the second case the cold vortex is at its developing phase and subtropical high is located more northward.The interaction between low and middle latitude atmospheres is remarkable,bringing a plenty of energy and water vapor.During the severe rainfall periods for both cases in Beijing,the features of mesoscale convective system(MCS),triggering mechanism and building of convective energy have significant differences.For the first case,meso-γMCSs are the main rainfall systems which developed in the stratiform cloud.Easterly wind not only supplies the lifting condition but also brings the warm and wet flow,working together with the upper-level dry and cold air intrusion,which finally causes the re-building of energy.However,for the second case,MCSs are featured by the well-developed meso-βsystems and the trainecho pattern is quite clear.The increase of energy is due to warm and wet flow transported by southerly low-level jet.The low-level jet and the cyclonic shear,accompanied by the appropriate terrai

关 键 词：华北冷涡 降水成因 预报偏差 对比分析 

分 类 号：P456[天文地球—大气科学及气象学] P458