Sensitivity of Tropical Cyclone Feedback on the Intensity of the Western Pacific Subtropical High to Microphysics Schemes

The Advanced Research version of Weather Research and Forecasting (WRF-ARW) Model is used to examine the sensitivity of a simulated tropical cyclone (TC) track and the associated intensity of the western Pacific subtropical high (WPSH) to microphysical parameterization (MP) schemes. It is found that the simulated WPSH is sensitive to MP schemes only when TCs are active over the western North Pacific. WRF fails to capture TC tracks because of errors in the simulation of the WPSH intensity. The failed simulation of WPSH intensity and TC track can be attributed to the overestimated convection in the TC eyewall region, which is caused by inappropriate MP schemes. In other words, the MP affects the simulation of the TC activity, which influences the simulation of WPSH intensity and, thus, TC track. The feedback of the TC to WPSH plays a critical role in the model behavior of the simulation. Further analysis suggests that the overestimated convection in the TC eyewall results in excessive anvil clouds and showers in the middle and upper troposphere. As the simulated TC approaches the WPSH, the excessive anvil clouds extend far away from the TC center and reach the area of the WPSH. Because of the condensation of the anvil clouds’ outflows and showers, a huge amount of latent heat is released into the atmosphere and warms the air above the freezing level at about 500 hPa. Meanwhile, the evaporative (melting) process of hydrometers in the descending flow takes place below the freezing level and cools the air in the lower and middle troposphere. As a result, the simulated WPSH intensity is weakened, and the TC turns northward earlier than in observations.