Influence of Two Types of Planetary Boundary Layer Schemes on the Intensity of Typhoon Rammasun (2014)

Abstract

The Weather Research and Forecasting model was adopted to perform simulations of Typhoon (TC) Rammasun (2014). Two local (QNSE and MYJ) and two nonlocal (GFS and ACM2) closure planetary boundary layer (PBL) schemes were selected to perform four groups of simulation tests. (1) PBL schemes have a minor influence on the TC track but exert a major influence on both the intensity and structure of the TC. TC track, intensity, and structure simulated by the local PBL schemes are close to observations, whereas TC intensities simulated by the nonlocal PBL schemes are slightly lower than the actual observed value. The local QNSE scheme generates the best simulation results. (2) TC intensity is closely related to variations in the TC structure. Of these schemes, the TC simulated by the local QNSE scheme has the largest intensity, the smallest eye zone, a complete eyewall, the strongest convection, the largest reflectivity, and the strongest tangential wind. (3) Differences in TC intensities are found under the joint action of thermal and dynamic factors. Regarding the local closure PBL schemes, the simulated values of the surface enthalpy flux, water vapor flux, and momentum flux are slightly higher, and the TC can be stronger accompanied by a higher PBL, stronger entrainment at the top of the PBL, and more intense vertical mixing. In addition, more intense vertical mixing can introduce surface energy into the upper air, resulting in the development of deep convection in stronger TC, an intensified warm core structure, and a higher warm center.

Keywords

• planetary boundary layer scheme
• typhoon intensity
• wrf model