On the Influence of Atmospheric Stability on the Wave Climate in a Warm and Saline Water Body

Abstract

This paper presents some of the challenges faced during a project aimed at preparing long-term wave climatology in the Persian/Arabian Gulf. Using the hourly CFSR wind fields as forcing, an attempt was made to produce a comprehensive hydrodynamic and sea state conditions data set. By comparing the wave results to various in-situ and satellite measurements, an obvious seasonal difference was observed. Wave conditions were well reproduced during winter while the wave height was generally overestimated and scattered during the summer period. After comparing the wind fields against measurements it was believed that other sources were playing an important role in wave growth and propagation. Based on available measurements, it was shown that in the summer period, where the air temperature is higher than the sea temperature, wave growth rate is lower than in the winter period. Similar real cases have been reported in some lakes, but the influence of atmospheric stability on wave climate in a relatively large sea like The Gulf has not been documented yet to the authors’ knowledge. This paper focuses on the importance of including atmospheric stability effects into wave modelling. In order to account for the stability effects, the friction velocity and surface roughness were modified in the 3rd generation wind-wave model, MIKE 21 SW, using the Monin-Obukhov similarity theory. Improvements were seen in the quality of modelled wave heights in the summer period. The Gulf is also highly affected by changes in the sea water density. The effects of varying water density on wave climate were also studied in this paper. In order to reproduce the best quality wave climatology in The Gulf, it was concluded that seasonal modelling is required and the effects of atmospheric stability should be included.