Tropical Cyclone Climatology and Hazard Estimations in a Warming Climate

Tropical cyclone (TC) hazard is associated with TC climatology, namely, the pattern of genesis, distributions of intensity and intensification rate, tendency of storm motion, and the frequency and intensity at landfall. These properties are sensitive to a warming climate, with an increasing storm intensity being the most certain change. Changes in other properties, such as genesis and landfall frequency are highly uncertain, especially on a regional scale. To estimate TC hazards in a warming climate is therefore challenging.

In this presentation, we will assess the TC hazards in a warming climate using the Columbia HAZard model (CHAZ). The CHAZ is a statistical-dynamical downscaling model which estimates TC hazard by generating synthetic storms using environmental conditions from a global model. CHAZ contains three components representing the complete storm lifetime: tropical cyclone genesis index (TCGI) model, a beta-advection track model and an auto-regressive intensity model. We will downscale CHAZ from six CMIP5 climate models simulations from historical and the Representative Concentration Pathway (RCP) 8.5 future scenario. Knowing the large uncertainty in the changes in TC climatology, instead of seeking for a single estimation of future TC hazards, we will show possible range in TC hazards in the future due to various changes in the TC characteristics. For example, to understand how changes in the genesis frequency in a warming climate will affect regional TC hazards, we will conduct three experiments. The first two will be using two different versions of a tropical cyclone genesis index (TCGI) – one with relative humidity as the moisture variable, the other with the saturation deficit – in CHAZ to generate the synthetic storms; these two indices have similar annual genesis frequency in the current climate but opposite trends as the climate warms. In the third experiment, we will use a random seeding approach to remove the dependence of CHAZ on TCGI. The resulting changes in TC climatology and hazards in a warming climate will then be analyzedfrom both global and regional perspectives.