采用Cloudsat/CPR云雷达,FY2C/TBB亮温,Aura/MLS大气成分等卫星遥感资料,结合ECMWF气象分析资料和HYSPLIT4轨迹模式,研究了2009年6月一次东亚切断低压的暖区深对流和异常副热带锋面的结构和演变.分析表明,由于低压切断前的旧槽背景,在低涡的近成熟期,内部冷、暖锋降水偏弱,边沿的高空副热带锋面异常发展到对流层底部,低空西南暖湿水汽在副热带锋前聚集,形成千公里长的暖区深对流降水带.随着该锋面的快速东移,副热带锋区进入原暖区雨带,锋区热力间接次级环流的强上升支,加强了锋下冷侧(原暖湿区)的深对流,但该锋面阻挡了来自暖侧的水汽补充,降水结束.该异常副热带锋区还发生了强烈的平流层-对流层相互交换,在高空急流出口区的下方,平流层1.5PVU等位涡线向下入侵可达5.5 km(约500 hPa)处,锋下向上的深对流注入可达10 km,在入侵-注入混合区,臭氧和水汽的散点图上出现了二者浓度双高和双低的特殊气团.
This paper studies a deep convection in warm sector and abnormal subtropical front caused by a cutoff low over East Asia in June 2009, by using cloud profile radar data from Cloudsat, temperature of black body from FY2C, atmospheric compositions from Aura/MLS, meteorological data from ECMWF and HYSPLIT4 trajectory model. The analysis shows that, for the sake of the background of southern trough, there are two weaker rain bands from theinner fronts, while nearly 1000 km scale deep convection occurs m warm sector, e,t the healey mature stage of the low, the subtropical front induced by the cutoff low is abnormally developing throughout whole troposphere, which is due to the warm and humid air from southwest gathering along the subtropical front. After rapid eastward moving of the front into rain belt in warm sector, the strong ascending branch of thermal indirect secondary circulation across the frontal zone enhances deep convection at the colder part below the front. But it is difficult to sustain because the supplement of water vapor is blocked by the abnormal front. Furthermore, intense stratosphere-troposphere exchange occurs in the abnormal subtropical front zone due to the convective injection into stratospheric intrusions. On the scatter plot of ozone and water vapor these are two special gathering areas with both high (low) concentrations of the two species.