Tropical Cyclone Rainfall Modeling and Hazard Assessment

Abstract

Heavy rainfall associated with tropical cyclones (TCs) is an important hazard producer, and climate change can significantly influence this hazard. Though our understandings of the physical mechanisms of TC rainfall have been advanced, the understandings of the climatological features of TC rainfall hazards, how TC rainfall hazard will change in the future, and how to better simulate and assess TC rainfall hazards, are still limited. This dissertation aims to improve the understandings of the abovementioned questions by studying TC rainfall hazards climatology using various numerical and statistical models. A physics-based TC rainfall model (TCR) is used in this dissertation for the TC rainfall hazard assessments. The model is first validated against historical observations, and then compared with the Weather Research and Forecast model to understand its ability to capture TC rainfall mechanisms. The intrinsic bias of TCR is corrected statistically and the bias of rainfall hazard assessments caused by synthetic storm simulation is then studied by examining the important TC-related parameters for TC rainfall hazards and the bias of these parameters in various synthetic storm models. To broaden the application of TCR model, a method for coupling TCR with engineered synthetic TCs is developed for rainfall hazard assessment. The TCR model is then coupled with synthetic storm models to evaluate the physical drivers of TC rainfall hazard change and assess sequential hazards associated with landfalling TCs. We obtain the following major findings in this study. TCR is found to be capable to reproduce climatological features of TC rainfall hazard. Using TCR, we found TC intensity, duration and distance to the studying points are three most important factors to determine TC rainfall hazard. The change of future TC rainfall is scaled as cube of TC intensity change. It is also found that the intensity change is the major driver for TC rainfall hazard increase comparing to other factors. The frequency of sequential TC hazard is projected to increase in the future, and the increase of TC rainfall hazard is an important factor causing the sequential hazards to be more frequent.