Ocean–Atmosphere Flux Calculation in Version 2 of the Spectral Flexible Global Ocean–Atmosphere–Land System Model

Abstract

To calculate flux exchange at the air–sea interface, the National Center for Atmospheric Research (NCAR) Coupler 6 is employed in version 2 of the spectral Flexible Global Ocean–Atmosphere–Land System Model (FGOALS2). Two parameterizations of surface fluxes are designed for the model. The first is a bulk aerodynamic scheme, and the second is a wind gustiness scheme, which is an improvementoverthe preliminarybulk aerodynamic scheme. The latter considers sub-grid wind variability, or wind gustiness, contributed by boundary layer large eddies and convective precipitation. The implementation of the wind gustiness scheme to FGOALS2 improves the simulation of sensible and latent heat fluxes except that the magnitude of sensible (latent) heat flux is underestimated (overestimated). A similar bias is also evident in the simulation employing the bulk aerodynamic scheme, indicating that the bias is dominated by other physical processes. The mesoscale enhancement of sub-grid wind in the wind gustiness scheme leads to a westward extension of the center of turbulent flux and an enhancement of the magnitude. Differences between the two schemes are also evident during El Niño–Southern Oscillation (ENSO) events; however, this mechanism requires further study.