Global Warming's Effects on Tropical and Extratropical Cyclone Tracks

Tropical cyclones (TCs) play a crucial role in Earth's energy and water cycles. Recurving TCs, and those undergoing extratropical transition (ET) are especially important in the North Atlantic and western North Pacific basins. These systems can impact major population centers outside of the tropics and  sub-tropics, as Irene (2011) and Sandy (2012) have recently demonstrated in the United States. Changes in the extratropical storm tracks in response to warming are difficult to ascertain because of offsetting physical processes. Weakened lower-tropospheric baroclinicity and increased tropospheric static stability in the sub-tropics argue for weaker storms and a northward shift in the storm track. Enhanced upper-tropospheric jets and increased water vapor content favor strengthening. Initial experiments led to the hypothesis  that warming would increase the strength of the fiercest cyclones, along with some diabatic storm-scale features such as the cyclonic low level jet (LLJ). The LLJ plays an important role in poleward heat and moisture transport, and can be associated with heavy precipitation and damaging winds. Furthermore, it was  hypothesized that the small spatial scale of storm-scale features which are most strongly influenced by latent heating led to under-representation of storm-track changes in coarse grain General Circulation Model (GCM) simulations. The outcomes of these tested hypotheses hold important implications for the interpretation of GCM output, as well as determining GCM resolution requirements. The research proposed here centers around two broad and related foci: (i) an investigation of how the intensity and frequency of recurving TCs, and those undergoing ET, will be affected by climate change; and (ii) an analysis of how the spatial and temporal distribution of tropical cyclogenesis may change with climate.