dc.description.abstract | A number of numerical modeling studies have focused on the effect of vertical wind shear on TC structure and intensity, but they mostly used idealized symmetric vortex in a sheared environment. In this study, the development of typhoons BILIS (2006) and KAEMI (2006) in environmental vertical wind shear is investigated using Weather Research and Forecasting model (WRF) with finest grid length of 3km and synoptic analysis, the impact of the vertical wind shear on these two typhoon cases will be examined and compared with the previous studies.
The result is shown that the simulated track is within 2° latitude–longitude of the RSMC best track at the end of the 2-day integration. The model also reproduces reasonably well on the hurricane intensity, intensity changes and asymmetries in precipitation. The simulated intensity is about 11hPa deeper in BILIS and 11hPa weaker in KAEMI, but same as observation, KAEMI is stronger than BILIS. The WRF also simulated the structure and evolution of precipitation very well. However, the simulated rainfall rate in BILIS is higher than observed, the errors are possible due to some deficiencies in the model physics and the simulated intensity was stronger than observed.
In agreement with earlier studies, BILIS and KAEMI quickly develop to wave number one asymmetries with upward motion and rainfall concentrated on the downshear side, and the maximum reflectivity rotate cyclonically.The storm continuously intensifies with the vertical shear during 2 days, this appears to contradict with the previous findings that the vertical shear tends to produce negative impact on the intensification of tropical cyclones. However, the effects of vertical wind shear on the development of convective asymmetry setructure are very obvious. On later simulated stage, the vertical wind shear of both cases increases fast, and inhibit the development of convective in the upshear side. When vertical shear tends to suppress cloud development of KAEMI in upshear side through descending inflow of air, the low and mid-level warming of KAEMI was more obvious than BILIS. It shows that warm core structure in the center of tropical storms is sensitive to storm size in the vertical wind shear environment. | en_US |