两种边界层方案对台风“Megi”路径的影响

Effects of Two Boundary Layer Schemes on the Track of Typhoon Megi

以WRF为试验模式,对比分析2种边界层参数化方案(YSU、MYJ)对台风"Megi"路径的影响。结果显示,"Megi"路径对边界层方案的变化有一定的敏感性。相比于MYJ方案的模拟结果,YSU方案模拟的边界层垂直混合作用和水汽垂直输送较强,因此对流层高层的水物质含量高于MYJ方案中的结果。分布于台风周围的水物质在对流层高层会以砧云的形态扩散至副高区域,砧云在对流层高层凝结放热增温,在低层形成降水蒸发吸热降温,影响副高区域上下层的温度分布,导致副高强度减弱、位置东退,最终造成台风提前转向。

Using the WRF model as an experimental model,we compared and studied the effects of two schemes of boundary layer parameterization,YSU and MYJ,on the track of Typhoon Megi. As shown in the result,the track of Megi shows some sensitivity to the change of the boundary layer scheme. Compared with the simulation with the MYJ scheme,the vertical mixing effect and vertical water vapor transport in the boundary layer simulated by the YSU scheme is stronger,and the content of hydrometeors is higher. The hydrometeors,distributed around Megi in the upper troposphere,spread to the area of the subtropical high in the form of anvil clouds to heat the atmosphere through condensation at the upper level and cool it by evaporation through precipitation at the lower level. As a result,the temperature distribution at the upper and low levels of the subtropical high is disrupted,causing the subtropical high to weaken and retreat to the east and eventually making the typhoon to turn earlier than usual.