Impact of tropical cyclone activity on future wind-wave climate

Recent studies have investigated how regional and global wave climate may change in the future, particularly in the context of global warming. The approach is often to project wave climate by using output from atmospheric circulation models, such as those run for the CMIP, either as input to statistical downscaling methods that determine the resulting waves, or as forcing for a numerical wind-wave model.

An important influence on the wave climate is the frequency and intensity of tropical cyclones (TC). In particular, they have a have a strong influence on the tail of the distribution of wind speed in affected regions, and are therefore a key element of any analysis of waves, particularly with respect to extremes. Owing to the computational cost, to date, many atmospheric models have been run at resolutions too low (~1.0 degree) to accurately reproduce TCs, and they remain a significant source of uncertainty. However, recent high resolution simulations (~0.25 degree) of atmospheric circulation show considerable improvement in the model's ability to simulate TCs.

Here we investigate their impact on waves globally, and in possible future climates, by forcing the global numerical wave model Wavewatch III, with high resolution output from the Community Atmosphere Model 5.1. We examine to what extent the simulated TCs contribute to the extreme wave climate, and present statistical theory to explain their relationship.