Resolution dependence of simulated extreme wave climate in the North Atlantic in a changing climate.

Abstract:

Recent studies have investigated how regional and global wave climate may change in a warmer world. The approach is often to project wave climate by using output from atmospheric circulation models, either as input to statistical downscaling methods that determine the resulting waves, or as forcing for numerical wind-wave models. An important influence on the wave climate is the frequency and intensity of tropical cyclones, but to date, many atmospheric models have been run at resolutions too low (~1.0 degree) to accurately reproduce such phenomenon, which in turn has lead to poor predictions of waves in affected regions. Tropical cyclones therefore remain an important source of uncertainty in projections of wave climate. However, output from recent high resolution simulations (~0.25 degree) of atmospheric circulation shows considerable improvement in the model's ability to simulate tropical cyclones. In order to investigate the importance of this issue on projections of waves, we present results of the analysis of wave climate in the North Atlantic, by forcing the global wave model, Wavewatch III, with both low and high resolution output from the Community Atmosphere Model 5.1, under atmospheric conditions of both the early 1990s, and conditions with a 2 degree increase in sea surface temperature and increased atmospheric CO₂. Extremes of the wave climatology in the North Atlantic are examined and the consequences for the U.S. eastern seaboard are discussed.