Two-sided turbulent boundary layer parameterizations for assessing ocean – atmosphere fluxes

Standard methods for determining air – sea fluxes typically rely on bulk algorithms derived from the Monin-Obukhov stability theory (MOST), using ocean surface fields and atmosphere near-surface fields. In the context of coupled ocean – atmosphere simulations, the shallowest ocean vertical level is usually assimilated to the surface, and the turbulent closure is one-sided: it aims at extrapolating atmosphere near-surface solution profiles (for wind speed, temperature and humidity) to the prescribed ocean surface values. Assimilating near-surface ocean fields as surface ones is equivalent to considering that in the ocean surface layer, solution profiles are constant instead of also being determined by a turbulent closure. Here we introduce a method for extending existing turbulent parameterizations to a two-sided context, by including the ocean surface layer and the viscous sublayers, which are also generally neglected in standard air – sea fluxes computation. The formalism we use for this method is derived from that of classical turbulent closure, so that our novelties can easily be implemented within existing formulations. Special care is taken to ensure the smoothness of resulting solution profiles. We investigate the impact of such two-sided bulk formulations on air - sea fluxes and discuss further implications such as resulting bulk formulation retuning. We also present leads on incorporating other mechanisms impacting air – sea fluxes within our framework, such as waves and radiation penetration.