Global Ocean Forecast System V3.0 Validation Test Report Addendum: Addition of the Diurnal Cycle
Abstract This report documents the ocean model response of adding diurnal variations to the incoming shortwave radiation forcing applied to the Global Ocean Forecast System Version 3.0. This can have a large impact on near surface ocean temperature and mixed layer, especially in low wind conditions when the near surface ocean is strongly stratified. This so called "afternoon effect" can warm the upper ocean forming a thin mixed layer, and have a profound impact on the sound speed profile and surface duct. Hindcasts of GOFS V3.0 show an improved representation of the near surface afternoon warming when compared to observations, although proper representation of the atmospheric forcing is crucial to accurately model this effect. Nonetheless, time series of observed and hindcast sea surface temperature and mixed layer depth show higher correlations when the diurnal cycle is included as opposed to when it is not included.