A diagnostic model of the diurnal cycle of sea surface temperature for use in coupled ocean‐atmosphere models

Abstract

On the basis of a method of estimating the diurnal amplitude of sea surface temperature (SST) as a function of the diurnal integrals of surface heat and momentum fluxes, a parameterization scheme of the diurnal cycle of SST is implemented in a one‐dimensional ocean mixed‐layer model. Many coupled ocean‐atmosphere models using bulk mixed‐layer schemes underestimate the diurnal cycle in sea surface temperature by up to 2°C. This discrepancy is caused by coarse vertical resolution in the upper grid boxes of the ocean components. A simple solution is suggested by adding one extra transient level: a variable‐depth diurnal sublayer within the top model level which accommodates the diurnal buoyancy cycle. A one‐dimensional mixed‐layer model with 10‐m resolution and with sublayer simulates diurnal SSTs close to those observed from the Tropical Ocean Global Atmosphere/Coupled Ocean Atmosphere Response Experiment (TOGA/COARE) with typical errors of about 0.1°C. The impact of improved SSTs on surface heat fluxes is also shown by coupling the one‐dimensional mixed‐layer model with sublayer to an atmospheric boundary layer model.