Turbulent transport of sea-spray in the coastal region

A realistic three-dimensionnal large-eddy simulation is performed for the study of turbulent transport of sea spray aerosol in the coastal region of Le Croisic, France. A new transport model for the aerosol is implemented in the ARPS code. Simulation results are compared with field measurements, both for the mean wind field and aerosol concentration. The numerical results fit well with the observations. The mean vertical concentration profile takes an exponential shape when the data is averaged over sufficiently long timeframe, whereas the 15-min averaged profiles vary and deviate from the theory. The transport of the aerosols is analyzed in relation to the sea-land transition and the changes in thermal stability of the atmosphere during the diurnal cycle. Turbulence is found to play an important role in the mixing of aerosols in the unstable surface layer. The turbulent vertical transport of aerosols is enhanced through convective cells over the land during the day, whereas, at night, aerosols remain trapped near the surface and are transported over appreciable horizontal distances under quasi-neutral or stable thermal conditions.