Assessing air-sea interactions at very high resolutions using the Dutch Atmosheric Large Eddy Simulation
Chris Chapman
Ocean and atmosphere interact by exchanging heat, momentum, and energy between the surface ocean mixed layer and the lower atmospheric boundary layer. Turbulent processes are fundamental to this exchange. However, in almost all atmosphere and ocean models, this turbulent exchange is handled by bulk-formulae that use a mix of theory and empirical relationships to estimate turbulent exchange from inputs with no explicit representation of turbulence. Do these bulk formulae hold up?
Here, we use the Dutch Atmospheric Large Eddy Simulation (DALES) that explicitly represents many turbulent processes to assess turbulent fluxes under a wide range of large-scale atmosphere and ocean conditions. Particular attention is paid to low wind speeds regimes in the tropics and subtropics, where turbulent processes are known to be both of leading order importance and harder to parameterize. We also assess how lower atmospheric turbulence responds to the diurnal cycle of ocean surface temperatures, which are typically not included in uncoupled atmosphere models driven by prescribed sea-surface temperatures.
Our results have important implications for both ocean, atmosphere and coupled modelling, particularly at higher resolutions, suggesting an important role for atmospheric turbulence and short time scale ocean variability even when wind speeds are low.
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