Bulk parameterization of air‐sea fluxes for Tropical Ocean‐Global Atmosphere Coupled‐Ocean Atmosphere Response Experiment

Abstract

This paper describes the various physical processes relating near‐surface atmospheric and oceanographic bulk variables; their relationship to the surface fluxes of momentum, sensible heat, and latent heat; and their expression in a bulk flux algorithm. The algorithm follows the standard Monin‐Obukhov similarity approach for near‐surface meteorological measurements but includes separate models for the ocean's cool skin and the diurnal warm layer, which are used to derive true skin temperature from the bulk temperature measured at some depth near the surface. The basic structure is an outgrowth of the Liu‐Katsaros‐Businger [Liu et al., 1979] method, with modifications to include a different specification of the roughness/stress relationship, a gustiness velocity to account for the additional flux induced by boundary layer scale variability, and profile functions obeying the convective limit. Additionally, we have considered the contributions of the sensible heat carried by precipitation and the requirement that the net dry mass flux be zero (the so‐called Webb correction [Webb et al., 1980]). The algorithm has been tuned to fit measurements made on the R/V Moana Wave in the three different cruise legs made during the Coupled Ocean‐Atmosphere Response Experiment. These measurements yielded 1622 fifty‐min averages of fluxes and bulk variables in the wind speed range from 0.5 to 10 m s−1. The analysis gives statistically reliable values for the Charnock [1955] constant (α = 0.011) and the gustiness parameter (β = 1.25). An overall mean value for the latent heat flux, neutral bulk‐transfer coefficient was 1.11 × 10−3, declining slightly with increasing wind speed. Mean values for the sensible and latent heat fluxes were 9.1 and 103.5 W m−2; mean values for the Webb and rain heat fluxes were 2.5 and 4.5 W m−2. Accounting for all factors, the net surface heat transfer to the ocean was 17.9 ± 10 W m−2.