A coupled modeling study of mechanical and thermodynamical air-ocean interface processes under sea storm conditions

Abstract

The interaction mechanisms between the lower part of the atmosphere and the ocean surface comprise of a complicated issue with many parameters to be studied. Heat, moisture and momentum exchanges in the air-sea system exert a significant role on both lower atmosphere and sea state conditions.Working towards the understanding of how wave characteristics link the atmosphere with the ocean, an atmospheric model is fully coupled with a wave spectral model. The RAMS/ICLAMS atmospheric model is integrated with the WAM wave spectral model under the OASIS-MCT coupler. The combined modeling system utilizes schemes for ocean surface roughness and sea spray droplet thermodynamics.A series of sensitivity tests related to midlatitude cyclones is performed to examine the associated effects of sea state and sea spray impact on wave conditions and lower atmosphere. Under increased wind conditions, sea drag is enhanced as illustrated in the case of the two-way coupling simulations. In addition, increased values of roughness length were traced in near-shore areas in the case of expressions that employ wave parameters such as the wave age. The magnitude and the role of energy yield from sea water droplets depend on the prevailing weather conditions. Sea spray fluxes are amplified in areas with intensified surface winds that also results in an increase of the total heat fluxes. This induces a moistening of the near surface air, an effect in stability profile and an increase of wind speed. The most noticeable impact on marine layer structure emerged close to the first hundred meters. The study revealed an enrichment of the description of the air-sea system through the transition of information between the different models.