An air-sea interaction model for stress, sensible heat, latent heat, and sea state, applicable to the full range of wind speeds

Mark Allan Bourassa, Purdue University

Abstract

An improved air-sea interface model has been developed. The model differs from others in that it is applicable to low wind speeds, as well as moderate and high wind speeds. Most interface models are not accurate at low wind speeds and, consequently, they underestimate fluxes in low wind speed regions, such as the tropical oceans. Results include a wave age parameterization that is valid for wind tunnels, as well as the open ocean. The model's improvements were achieved through the development of a capillary wave roughness length parameterization and an improved sea state model. The theory behind these improvements is described. The flux model results are contrasted with surface fluxes obtained from the popular LKB model and from the 1988-1992 ECMWF parameterization. Data from a pre-TOGA-COARE IOP cruise were used to evaluate the accuracy of the models. At low wind speeds the ECMWF model was found to strongly underestimate fluxes of latent and sensible heat. The low wind speed results of the model discussed herein are similar to the LKB results; however, the high wind speed results of the new model more closely resemble those of the ECMWF parameterization. A comparison is made among bulk fluxes from the tropical Pacific ocean (30$\sp\circ$S to 30$\sp\circ$N and 140$\sp\circ$E to 90$\sp\circ$W). The surface data used for input into the models came from the ECMWF surface fields on the TOGA CD ROM data archive. For low wind speeds, the fluxes estimated by the new model are of greater magnitude than fluxes predicted by the ECMWF and LKB models. A strong dependence upon atmospheric stability is evident in the bulk fluxes. The important influence of atmospheric stability is confirmed in a sensitvity study of the new model.

Degree

Ph.D.

Advisors

Vincent, Purdue University.

Subject Area

Atmosphere|Oceanography

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