Tropical Cyclogenesis and Climate: Physical Basis, Predictability and Prediction

Georgia Tech Research Corporation, Atlanta GA

Investigators

Abstract

Deficiencies in knowledge of tropical cyclogenesis hamper the ability to make forecasts of individual tropical cyclones (TCs) beyond about 5 days. Further, there is a limited physical basis for inferring TC characteristics from low-resolution reanalysis products and climate model simulations. Furthermore, scientists have been unable to make any substantive progress in determining a link between hurricane and global warming, owing to current reliance on flawed data sets and coarse resolution models. The Principal Investigators (PIs) are addressing these uncertainties and deficiencies through theoretical analysis, a comprehensive analysis of existing data, model experimentation and predictive scheme development. They will use a combination of observation data sets and models to investigate: (i) Genesis tropical cyclones: They will re-examine the genesis criteria developed by Gray (1968) a number of decades ago, to assess their utility and validity in the context of improved data sets, increased theoretical understanding, and changes in the base state of the climate. (ii) TC genesis predictability and predictions: Based on the development of a new set of TC genesis factors, the PIs will construct a hybrid dynamical-empirical Bayesian model for the forecasting the probabilities of TC risk in the 7-30 days forecast horizon. (iii) TC intensity and frequency in a warming world: The PIs will use the ARW (Advanced Research Weather Research and Forecasting) and CMIP-3 (Climate Change Climate Model Inter-comparison Program's) simulations to investigate the following hypotheses: * Average TC intensity will increase in the warmer climate, and there will be a shift in the intensity distribution towards more category 4 and 5 TCs; * The frequency of TCs outside the North Atlantic will remain roughly constant in a warmer climate, while the frequency of North Atlantic TCs will increase slightly; * TCs will continue to predominate in the summer hemisphere even if the winter hemisphere sea surface temperatures are sufficiently warm; * TCs are substantial contributors to the poleward energy transports across 30 degrees north in the present climate and will remain so in a warmer climate; * TCs are substantial contributors to the vertical transport of heat and moisture in the atmosphere, both in the present and warmer climate. Intellectual merit: This research will result in improved understanding of the conditions for the formation of tropical cyclones. This improved understanding will lay the foundation for improved projections of tropical cyclone activity over a range of time scales and in a warming world. Broader Impacts: The socioeconomic impact of improved tropical cyclone forecasts and assessments of TC characteristics for the next century are substantial. The PIs are very active in public outreach education on the topic of hurricanes and climate change, and will continue to interact with policy makers, emergency managers, and the private sector.