Numerical Study on the Genesis of Incipient Vortex of a Tropical Storm over the South China Sea. Part II Sensitivity of Sea Surface Sensible Heating

Abstract

The experiments are conducted to determine the impact of the anomalous surface sensible heating (SH) from the South China Sea (SCS) on the incipient vortex of the storm Mindulle (2010) formation by using the Weather Research and Forecasting (WRF) model, including the control-run with and the sensitivity-run without such heating. Significant impact is seen, with the incipient vortex failing to generate without the related SH. Based on the atmospheric thermal adaption theory, the outputs reveal that the genesis of the incipient vortex can be divided into the formation stage and the strengthen stage. At the formation stage, the surface SH favoured the enhancement of the surface convergence. Thus strong westerlies and southerlies along with the topography forcing constrain updrafts over the Luzon Island. The non-uniform condensation latent heating (LH) released by the vertical motion creates the cyclonic vorticity in the lower atmosphere, which was conducive to the incipient vortex formation. At the strengthen stage, the more intense LH due to the enhanced ascending motions mainly contributed to cyclonic vorticity generation. Therefore, the incipient vortex continuously strengthened and attained to the intensity of tropical storm. The simulation results illustrate that the development of the Mindulle (2010) is a “bottom-up” process.