The effects of rainfall on the ocean at low wind speed

The top few meters of the oceanic boundary layer, or surface-wave zone, play a crucial role in the transfer of momentum, heat and mass (gas and aerosol) between the atmosphere and the ocean. These exchanges are essential to weather, global climate and the general circulation of both the atmosphere and the ocean. In general, the surface-wave zone is well mixed by the wind which generates waves and shears currents and thus provides the necessary energy input and turbulence to produce significant mixing. However, our knowledge of the effect of rain on near surface dynamics is extremely poor. The available data are, for the most part, focused on the damping of the wave field by rainfall. Indeed, among the sea-going community, it is well known that rain has the unexpected effect of ``calming the sea'', but the scientific community has yet to clearly identify a mechanism, despite the dramatic implications for ocean surface remote sensing.