Radiation Feedback Accelerates the Formation of Typhoon Haiyan (2013): The Critical Role of Mid‐Level Circulation

Abstract

Abstract The prediction of tropical cyclones (TC) genesis remains a great challenge. This study shows that the radiation (mostly cloud‐radiation) feedback accelerates the formation of Typhoon Haiyan (2013) by first enhancing the mid‐level circulation. Simulations indicate that the response of the mid‐level circulation is about one day ahead of the low‐level circulation when radiation feedback is removed. The radiation‐heating anomaly in the disturbance region induces a secondary circulation transporting more water vapor upward at high levels. Thus, the stratiform precipitation is enhanced, manifested as the expansion of the stratiform coverage and the increase of the vertical gradient of latent heating. This leads to a stronger mid‐level potential vorticity production and enhancement of the mid‐level circulation, finally promoting TC genesis. Comparing with previous ideas on how radiation feedback accelerates TC genesis, our results emphasize the critical role of the mid‐level circulation and the cloud‐radiation‐induced thermodynamical and dynamic responses in the vertical.

Keywords

• cloud radiation
• mid‐level vortex
• radiation feedback
• tropical cyclogenesis
• tropical cyclone