A Numerical Study on the Effect of an Extratropical Cyclone on the Evolution of a Midlatitude Front  

作　　者：陈光华 

机构地区：[1]Center for Monsoon System Research, Institute of Atmospheric Physics, Chinese Academy of Sciences

出　　处：《Advances in Atmospheric Sciences》2013年第5期1433-1448,共16页大气科学进展（英文版）

基　　金：supported by National Basic Research Program of China (Grant No. 2009CB421505);National Natural Science Foundation of China (Grant No. 41275001)

摘　　要：The extratropical transition （ET） of tropical cyclone （TC） Haima （2004） was simulated to understand the impact of TC on midlatitude frontal systems. Two experiments were conducted using the Advanced Research version of the Weather Research and Forecast （WRF） model. In the control run （CTL）, a vortex was extracted from the 24-hour pre-run output and then inserted into the National Centers for Environmental Prediction （NCEP） global final （FNL） analysis as an initial condition, while TC circulation was removed from the initial conditions in the sensitivity run （NOTC）. Comparisons of the experiments demonstrate that the midlatitude front has a wider meridional extent in the NOTC run than that in the CTL run. Furthermore, the CTL run produces convection suppression to the southern side of the front due to strong cold advection related to the TC circulation. The easterly flow north of the TC not only decelerates the eastward displacement of the front and contracts its zonal scale but also transports more moisture westward and lifts the air along equivalent potential temperature surfaces ahead of the front. As a result, the ascending motion and diabatic heating are enhanced in the northeastern edge of the front, and the anticyclonic outflow in the upper-level is intensified. The increased pressure gradient and divergent ftow aloft strengthen the upper-level jet and distort the trough axis in a northwest-southeast orientation. The thermal contrast between the two systems and the dynamic contribution related to the TC circulation can facilitate scalar and rotational frontogenesis to modulate the frontal structure.The extratropical transition （ET） of tropical cyclone （TC） Haima （2004） was simulated to understand the impact of TC on midlatitude frontal systems. Two experiments were conducted using the Advanced Research version of the Weather Research and Forecast （WRF） model. In the control run （CTL）, a vortex was extracted from the 24-hour pre-run output and then inserted into the National Centers for Environmental Prediction （NCEP） global final （FNL） analysis as an initial condition, while TC circulation was removed from the initial conditions in the sensitivity run （NOTC）. Comparisons of the experiments demonstrate that the midlatitude front has a wider meridional extent in the NOTC run than that in the CTL run. Furthermore, the CTL run produces convection suppression to the southern side of the front due to strong cold advection related to the TC circulation. The easterly flow north of the TC not only decelerates the eastward displacement of the front and contracts its zonal scale but also transports more moisture westward and lifts the air along equivalent potential temperature surfaces ahead of the front. As a result, the ascending motion and diabatic heating are enhanced in the northeastern edge of the front, and the anticyclonic outflow in the upper-level is intensified. The increased pressure gradient and divergent ftow aloft strengthen the upper-level jet and distort the trough axis in a northwest-southeast orientation. The thermal contrast between the two systems and the dynamic contribution related to the TC circulation can facilitate scalar and rotational frontogenesis to modulate the frontal structure.

关 键 词：numerical study extratropical cyclone midlatitude front 

分 类 号：P444[天文地球—大气科学及气象学]