SeaCluse: Numerical simulation of evaporating sea spray droplets

The SeaCluse computer code calculates the nonlinear interactions between se a spray droplet concentrations and the scalar fields of water vapor concent ration and temperature in the marine atmospheric surface layer. The code si mulates most of the dynamics of the evaporating sea spray droplets in the t urbulent air flow over a wavy surface, the thermodynamic transformations of the spray droplets, and the influence of the droplets on the structure of the lower marine atmosphere. The main processor computes along the vertical the horizontally averaged budgets of droplet concentration, water vapor co ncentration, and sensible heat, including the dynamic and thermodynamic air -droplet interactions. This paper presents the first simulations of evapora ting sea spray droplets made with the SeaCluse model. It is shown that comm on assumptions such as exponential vertical concentration profiles and the evaporation of all droplets to their equilibrium radius do not necessarily hold for droplets with a radius larger than similar to 30 mum. The present results also demonstrate the importance of the nonlinear interactions betwe en sea spray droplets and the scalar fields of water vapor and temperature. Most droplets evaporate close to the surface, in a layer of similar to2-3 times the wave height. The impact of evaporating sea spray droplets increas es rapidly with increasing wind speed.