Mesoscale Air-Sea Interaction during the Passage of a Typhoon over the Yellow and East China Seas

Abstract

In order to best capture the mutual forcing and feedback process to improve the accuracy of modeling of the mesoscale process, we developed the two-way coupling model MCM (Mesoscale Coupled Model) based on two independent models, the atmospheric model MM5v3 and the ocean model ECOM-si, using a flux coupler designed with the concurrent process communication technique. We selected Typhoon Winnie (9711) passing over the Yellow and East China Seas (YECS) to test the performance of the coupling model, and analyzed the quantitative impacts on atmospheric and oceanic variations. The results show that the simulated air-sea heat and momentum exchanges strongly affect circulation in both the atmosphere and the ocean. When mesoscale air-sea interaction is considered, the results for the atmosphere and ocean improved considerably. In terms of atmosphere, the air-sea interaction updates the distribution of elements (e.g., wind, heat flux, relative humidity and temperature) in the vertical and horizontal fields. The forecast result of typhoon intensity becomes more realistic, with decreases in central pressure error of 3.4 hPa at 30 hr and 9 hPa at 60 hr. A strong wind drives the cyclonic ocean current in the upper layer and induces horizontal transport and vertical mixing. All of these processes directly influence the Sea Surface Temperature (SST), which decreases over a large area, particularly near the typhoon center, and can reach 5 degrees C. Finally, we discuss a possible negative feedback mechanism.