Projection of Significant Wave Height in a Coastal Area under RCPs Climate Change Scenarios

Abstract

This article provides multimodel and multiscenario projections of significant wave height for the Qatar coast. Significant wave height is used for practical purposes such as offshore and coastal structure design as well as transport of marine and lake pollutants. It is mainly driven by near-surface wind speed. In this paper, the outputs of the different general circulation models (GCMs), under RCP (representative concentration pathways) emission scenarios RCP26, RCP45, RCP60, and RCP85, were used to project the monthly probability distribution of wind speed over the coastal areas. The simulations are part of the Coupled Model Intercomparison Project-Phase5 (CMIP5) experiment. Two statistical downscaling techniques are used: the Quantile-Quantile transformation and nearest neighbor search. Observed wind speed at the Doha Airport station was used as a proxy for wind speed over Qatar coast. The GCM-simulated wind speeds as well as minimum and maximum temperatures were used as predictors while the observed wind speed is used as predictand in the nearest neighbor method. In the Quantile-Quantile approach, the GCM-simulated wind speed is the sole predictor. These two techniques were assessed by comparing the probability distribution of the observed and corrected (downscaled) wind-fields. Finally, the projected wind speed was used to estimate the expected changes in significant wave height under climate change. Results show that: (1) both methods can reasonably reproduce the shape of the daily wind-speed probability distribution function at the study location but the nearest neighbor method is inappropriate for extreme wind speed estimation in the future; and (2) the Quantile-Quantile method suggests that significant wave height can increase up to 40% on the Qatar coast.