High-resolution Modeling Studies of the Changing Risks of Damage from Extratropical Cyclones

Studies have shown that global climate models can miss some of the mesoscale features important to cyclone development. These models tend to have grid spacing on the order of 100s of kms. This study uses a limited area model with 120 km to represent a climate scale simulation and 20 km spacing for a high-resolution simulation. We expect the high-resolution simulation to better resolve these features and provide insight into how strong extratropical cyclones could change in a changing climate. This is important for the insurance and reinsurance industry where capturing the intensity of a strong system is necessary to adequately quantify the risk.
Seasonal results are emphasized for the higher-resolution 20km simulation, which consistently resolved stronger winds not captured in the coarser resolution model run. A case study of strong extratropical cyclone “Xynthia” is also simulated in current and future climates. Cyclone Xynthia was weaker and made landfall sooner in the future simulation. The seasonal results provided enough data to utilize extreme value statistics in the analysis. The results showed that the top 2% of storms strengthened in the future simulation for areas in the British Isles and Europe. This is different than what was found in the case study where the storm got weaker in the future simulation. It appears that in the future seasonal simulations the most extreme storms are frequently different storms than in the current simulations.

Cipullo, M. High-resolution Modeling Studies of the Changing Risks of Damage from Extratropical Cyclones, North Carolina State University, Master of Science Thesis, Marine, Earth & Atmos Sciences, 2013