Observational and Numerical Studies of Tropical Cyclone Landfall Processes

Tropical cyclones (TCs), commonly known as typhoons in Asia, represent one of the most destructive weather phenomena. Every year, ~ 15-20 TCs make landfall in the Asian region, resulting in many disasters such as severe flooding due to heavy rain and storm surge, landslides, capsized vessels, and destruction of houses and buildings. Accurate predictions of TC landfall are therefore crucial in saving lives and property, which can only come about through better understanding of the physical processes involved. For this reason, the study of TC landfall processes is listed as the top priority in the most recent Strategic Plan of the Working Group on Tropical Meteorology Research (of which the PI is a member) of the World Meteorological Organization of United Nations. However, relatively few studies have been made on TC landfall, especially for the Asian region. It is therefore imperative that much more research should be done to understand the mechanisms leading to changes in various characteristics of the TC (track and wind and rainfall distributions), which is the objective of this proposed project.Specifically, the objectives of the project areto identify various changes in track and structure (wind and convection distributions) of tropical cyclones before, during and after their landfall, andto understand the physical mechanisms that cause such changes through diagnostics of observations and numerical simulations.Results from this study will significantly improve our understanding of the changes in track and structure of TCs as they approach land, which will help forecasters know what to expect for a TC with certain characteristics, and hence make more accurate forecasts, which has been a big problem during the most critical time of 24 to 48 hours prior to landfall. The observational analyses as well as real-case simulations will focus on TCs making landfall along the China coast, and thus directly benefit forecasters in China in their forecasting of tropical cyclones approaching the China coast, and help contribute towards disaster prevention, mitigation and reduction. From a scientific perspective, this study will provide insights into how friction and moisture discontinuities as well as topography arising from a TC approaching land can modify the TC circulation and affect its dynamic and thermodynamic energy balance.