摘要
利用1°×1°的NCEP再分析资料、地面逐小时的观测资料和红外云图,对2007年7月18日的济南大暴雨过程进行了详细的α中尺度分析,揭示了地面β中尺度气旋新生发展的一种物理机制,并重点分析了多尺度的积云并合过程对此次强降水形成的重要作用。研究结果表明:在一个已经发展成热的MαCS的左后侧出现的下沉冷出流在低层向西南方向扩散,与午后不断加强的西南暖湿气流共同作用增强了地面的斜压性,从而使地面辐合线上的气旋性扰动加强,并迅速新生发展出β中尺度气旋。在此次强降水过程中共经历了从γ中尺度对流单体到β中尺度对流云团,再到α中尺度对流云团,最后形成中尺度对流复合系统的4个多尺度积云并合过程,而地面β可尺度气旋在每一个阶段都扮演了非常重要的角色,它们既是β中尺度对流云团的组织者,同时也是α中尺度对流云团的组成者,α中尺度对流云团往往都由一个以上的β中尺度气旋组织而成,当β中尺度气旋出现遭遇、合并之时,对流云团和降水得以强烈发展。在济南强降水发生前的1个多小时内,其西南方边界层内不断出现β中尺度超低空西南急流,它促使这一区域内不断产生回波单体并在向东北方向移动的过程中迅速发展成强回波带,当济南北面的强回波南移与这一强回波带并合后快速发展产生强降水。
A meso-βscale analysis is made on the torrential rain process occurred in Jinan in 18 July 2007 based on the 1°×1°NCEP reanalysis data,the surface-observed hourly rainfall data and the FY-2C IR satellite images.The physical mechanism for the formation and evolvement of the surface meso-βscale cyclone is revealed.Furthermore,the impact of multi-scale merging processes on the torrential rain is especially studied.It is found that the sinking cold flows diffused southwest in the low level at the left rear of the developed mature MαCS,which enhanced the baroclinicity near sutace under the joint effect with the southwest warm moist flows strengthened continually since afternoon with the result that the cyclonic disturbance over the surface convergence line was intensified and the meso-βscale cyclones are generated and developed quickly.The mesoscale convective systems experienced a multi-scale cloud merging process including four stages from the meso-γscale convective cell,to the meso-βscale and then the meso-αscale convective cluster,and finally to the mesoscale conveclive complex system.During every stage,the surface meso-βscale cyclones had played an important role,which were an organizer for both the meso-βscale convective cluster and the meso-αscale convective cluster.With the encounter and merger of meso-βscale cyclones,the conveclive cluster organized by more than one meso-βscale cyclones was intensively developed and the rainfall was enormously strengthened.During the more than one hour before the torrential rain event occured in Jinan,there were the meso-βscale super-low-level jets emerging continuously in the southeastern boundary layer,which stimulated the echo cells to emerge successively in this area and grew into a strong echo band during their moving northeast.When the strong echo north of Jinan moved southwardly and encountered with this strong echo band,they combined with each other and developed quickly,which resulted in the severe rainfall.
出处
《气象学报》
CAS
CSCD
北大核心
2010年第6期944-956,共13页
Acta Meteorologica Sinica
基金
国家自然科学基金项目(40975025)
关键词
济南大暴雨
β中尺度分析
β中尺度气旋
积云并合
Torrential rain event in Jinan
Meso-βscale analysis
Meso-βscale cyclone
Cloud merger
