Evaluation of CMIP5 and CORDEX derived wave climate in Indian Ocean

Abstract

The effects of climate change are currently a widely investigated issue. However, little attention has been paid to the effects of climate change on regional wave climate. With the growing need towards developing future projections of waves to assess climate-driven impacts on coastal processes, it is required to evaluate the performance of General Circulation Models (GCMs) and Regional Climate Models (RCMs) in simulating wave climate independent of their ability to simulate other standard variables. Near-surface winds, derived from GCMs participating in the Coupled Model Intercomparison Project (CMIP5) and RCMs from Coordinated Regional Climate Downscaling Experiment (CORDEX), are used to force a spectral wave model to simulate hindcast waves over Indian Ocean (IO) region. The GCM and RCM forced climatological wave characteristics (significant wave height, mean wave period, and mean wave direction) are compared with reanalysis data derived from ERA-Interim for performance evaluation. RCMs work at fine resolution and are assumed to simulate regional climate better than GCMs. However, we identified that there is no added value in simulating wave climate using RCMs. We also identified that there is no improvement in wave simulation upon choosing a fine resolution GCM (~ 1.4°) over a coarse GCM (~ 2.5°). Seasonality in wave characteristics is an important aspect in the IO. The skill of climate models in capturing seasonality was also evaluated. It is observed that ensemble GCM forced wave simulations capture seasonality better than other models. Finally, it is recommended to use ensemble GCM wind forcing for better wave simulation in the IO region.