超强不稳定和弱切变环境下一次飑线过程的雷达资料同化与分析  

THE RADAR DATA ASSIMILATION AND ANALYSIS OF A SQUALL LINE UNDER ULTRASTRONG INSTABILITY AND WEAK VERTICAL WIND SHEAR

作　　者：曹倩[1] 张述文[1] 曹帮军[1] 叶丹[1] 邱学兴 

机构地区：[1]兰州大学大气科学学院/甘肃省干旱气候变化与减灾重点实验室,甘肃兰州730000 [2]安徽省气象台,安徽合肥230031

出　　处：《热带气象学报》2016年第5期645-655,共11页Journal of Tropical Meteorology

基　　金：国家重点基础研究发展计划(973计划)(2013CB430102);国家自然科学基金项目(41575098);高等学校博士学科点专项科研基金项目(20120211110019)共同资助

摘　　要：利用中尺度模式WRF及其3DVar同化系统,对武汉附近多普勒雷达资料进行循环同化,并结合NCEP FNL分析资料、自动站降水资料、雷达回波和探空资料,对2011年7月26日发生在湖北的一次飑线过程进行环境条件分析和同化研究。探空显示:此次飑线发生在超强不稳定和弱的风垂直切变环境中。雷达回波表明:系统内存在东北-西南向和西北-东南向的两条回波带,前一条为飑线主体,在发展和成熟过程中缓慢移动;后一条的西北段快速减弱,而东南段逐渐与前一条合并。利用同化雷达资料后的模式预报场诊断分析表明:初期,虽然动力抬升条件不利于单体的新生和发展,但强不稳定能量却为其提供了强热力抬升条件;在发展期,低层风垂直切变和冷池虽然向有利于飑线发展的方向演变,但强度仍然较弱,而不稳定能量仍起主要作用,飑线是在不断增强的动力抬升和强热力抬升共同作用下逐渐成熟;后期,环境中不稳定能量大减,冷池强度也明显强于低层风垂直切变,动力和热力条件均不利于飑线进一步维持,飑线衰亡。With the mesoscale model WRF（ Weather and Research Forecasting） and a corresponding 3DVar assimilation system, Doppler radar data in Wuhan are assimilated. Then, a squall line that formed in Hubei on July 26, 2011 is investigated by using the data assimilation results, NCEP FNL data, observed precipitation data, radiosonde observations as well as observations of Doppler radars. The radiosonde observations show that the squall line is formed under the environment condition of weak low-level vertical wind shear and strong convective instability. The Doppler radar observations show two strong convective lines respectively in the directions of Northeast-Southwest and Northwest-Southeast; the first one moves slowly during its organization period,, the northwest side of the second one disappears rapidly and the southeast side merges into the first one. Diagnostic analysis by using the forecasts with assimilated radar data indicates that during the initial period, the dynamical condition is not beneficial to the formation and development of new convective cells, but the strong convective instability energy provides strong thermal lifting condition. Later on, low-level ambient vertical wind shear and a cold pool become in favor of development of the squall line, but dynamical lifting condition is weak and the convective instability energy still plays the vital role. With the increase of dynamical lifting and strong thermal lifting, the system gradually becomes mature. Finally, the convective instability energy releases, the strength of the cold pool becomes much stronger than the low-level vertical wind shear, and the squall line disappears.

关 键 词：资料同化 多普勒雷达 飑线 对流不稳定 低层风垂直切变 冷池 

分 类 号：P458.2[天文地球—大气科学及气象学]