相似路径台风“摩羯”(1814)和“温比亚”(1818)影响南通降水差异成因分析

Analysis on precipitation difference in Nantong influenced by similar track typhoons Yagi(1814)and Rumbia(1818)

为探讨相似路径台风“摩羯”(1814)和“温比亚”(1818)影响南通降水的差异原因,从天气形势、物理量场等方面进行分析,利用水汽通量、假相当位温、湿位涡、垂直螺旋度等物理量对降水进行诊断,得到以下主要结论:1)两台风移动路径主要受副热带高压和冷空气的影响,副热带高压边缘气流为主要引导气流。两台风均有追随200 hPa辐散中心移动的趋势。2)较强冷空气的侵入、鞍形场中的缓慢移动、强正涡度和强盛上升运动、强水汽输送且低空长时间水汽辐合、大气斜压性增强和风垂直切变增大均是台风“温比亚”造成南通更强降水的原因。3)水汽通量辐合增强,低层正涡度中心、强上升运动,低层假相当位温大值区叠加上空假相当位温梯度带,垂直螺旋度增大与正值发展高度均与台风强降水有明显对应。

In order to analyze the precipitation difference in Nantong influenced by similar track typhoons Yagi(1814)and Rumbia(1818)in Nantong,the synoptic situations are analyzed and the physical quantities such as water vapor flux,pseudo-equivalent potential temperature,moist potential vorticity(MPV)and vertical helicity are diagnosed in this paper.The main conclusions are as follows.1)The tracks of the two typhoons are mainly affected by the subtropical high and cold air,and the air flows at the edge of the subtropical high guide the typhoons.Both typhoons follow the movement trend of divergence center at 200 hPa.2)The intrusion of strong cold air,the slow movement in the saddle field,the strong positive vorticity and intense ascending movement,the strong water vapor transport and long-term low-layer water vapor convergence,the enhancement of atmospheric baroclinicity and the increase of wind vertical shear are all the reasons for the heavier precipitation caused by Typhoon Rumbia.3)The heavy precipitation has a good correspondence with the increases in water vapor flux convergence,the positive vorticity center,the intense ascending movement in the lower layer,the large values of the pseudo-equivalent potential temperature in the lower layer overlapped by the upper gradient of the variables,the increase and development height of the vertical helicity.