MECHANISM ANALYSIS FOR THE DIFFERENCE IN SIMULATED TRACK OF TROPICAL CYCLONE MEGI (2010) WITH TWO PLANETARY BOUNDARY LAYER SCHEMES

Abstract

The WRF model was employed to simulate super typhoon Megi (2010) with the YSU and MYJ planetary boundary layer (PBL) schemes respectively. The sensitivity of the simulated tropical cyclone (TC) track to the PBL scheme was investigated, and the mechanism for the impact of the PBL scheme on TC track simulation was analyzed from the perspective of TC size. The results show that the description of the vertical mixing process with different schemes is the primary reason for the difference in the simulated lower-level vertical transport of water vapor. Compared to the MYJ scheme, which could well reproduce Megi's track, the simulation with the YSU scheme produced more active outer spiral rainbands and larger TC size. Accordingly, the increased pressure gradient and radial wind led to more air mass transport from the western Pacific subtropical high (WPSH) to TC, resulting in a weakened WPSH and the large scale steering flow was changed subsequently. As a result, the simulated TC with the YSU scheme turned northward earlier than observation.