Efficient and Accurate Bulk Parameterizations of Air–Sea Fluxes for Use in General Circulation Models

Abstract

Efficient and computationally inexpensive simple bulk formulas that include the effects of dynamic stability are developed to provide wind stress, and latent and sensible heat fluxes at the air?sea interface in general circulation models (GCMs). In these formulas the exchange coefficients for momentum and heat (i.e., wind stress drag coefficient, and latent and sensible heat flux coefficients, respectively) have a simple polynomial dependence on wind speed and a linear dependence on the air?sea temperature difference that are derived from a statistical analysis of global monthly climatologies according to wind speed and air?sea temperature difference intervals. Using surface meteorological observations from a central Arabian Sea mooring, these formulas are shown to yield air?sea fluxes on daily timescales that are highly accurate relative to those obtained with the standard algorithm used by the Tropical Ocean Global Atmosphere Coupled Ocean?Atmosphere Response Experiment (TOGA COARE), where the latter includes the effect of dynamic stability in calculating wind stress and air?sea heat fluxes. Direct comparisons in calculating the wind stress, and latent and sensible heat fluxes with these formulas and the TOGA COARE algorithm demonstrate that the methodology presented here is computationally inexpensive because iterative calculations are not required in the present methodology. Wind stress and air?sea fluxes can be calculated ≈30 times faster with these bulk formulas than by using the TOGA COARE algorithm. This methodology is of direct practical value for GCMs of high spatial resolution, where the severe computational demands of performing GCM simulations encourage computing air?sea fluxes in the most computationally efficient manner possible. The combination of accuracy and ease of computation of this method makes it the preferred one for computing air?sea fluxes in such GCMs.