| To examine the impact of natural and anthropogenic climate variability on tropical cyclone (TC) tracks, a comprehensive analysis is conducted examining changes in TC tracks from changes in the large-scale steering flow and TC genesis for different climate scenarios. A Beta and Advection Model is used to create tracks under the different climate scenarios, which are then analyzed focusing on each contribution from changes in the large-scale steering flow and TC genesis separately and as a combined impact. Two experiments are conducted; the first examines potential changes in TC tracks due to anthropogenic climate change in the North Atlantic and Western North Pacific. The impacts of anthropogenic climate change on TC tracks are robust across models and potential future scenarios for changes in CO2. For the North Atlantic and Western North Pacific, there is a statistically significant decrease in TC tracks that move straight, impacting the Gulf of Mexico and Western Caribbean, or the Philippines, and a statistically significant increase in TC tracks that recurve into the open ocean. These changes are predicted to be small for any given area, with a change of ~1-5 TCs per decade and are found to be primiarly due to changes in the large-scale steering flow; however, small changes in TC genesis still contribute, especially in the North Atlantic. The second experiment examines potential TC tracks during the Last Glacial Maximum. The Last Glacial Maximum had a substantially different climate from present day allowing for an analysis on the impact of climate variability with a larger magntitude of change. Through comparing model-simulated tracks in the Pre-industrial Control and the Last Glacial Maximum, a global decrease in TC tracks is found, expect in the Central North and South Pacific. Unlike in the anthropogenic experiment, changes in TC genesis are the primary contributor to proposed differences in the TC tracks. Further analysis of the parameters that are used to calculate TC genesis show that unfavorable TC genesis conditions including cooler relative sea surface temperatures, drier mid-level moisture, and stronger vertical wind shear contribute to the decrease in TC genesis. In the regions where an increase in TC genesis is found, it is primarily a reduction in vertical wind shear and a warming of the relative sea surface temperatures that contribute. |
