Effects Of Sea Spray And Wind Sea Conditions On Air-sea Heat Flux

The COARE model is the commonly used algorithm in the world for air-sea heat flux, which is believed to be applicable to wind speed up to 20m/s.The theoretical basis and parameterization of variables of COARE3.0 version algorithm is reviewed. Results indicate that ocean current speed does not have significant effect on the heat flux. A pressure level of constant 1008hpa is adequate in sensible heat flux calculation. In terms of latent heat flux, observed pressure should be taken into accounted, when the pressure is less than 1000 hpa. Rain-induced sensible heat flux, which accounts for about 19.89% of the interface total heat flux, is not negligible. Differing from CNK and TAY algorithm, OST algorithm is very sensitive to low wave age.However, it is probably unreasonable to apply this model directly to the condition with wind speeds higher than 20m/s, because of the absence of the impact of sea spray in the model, which always appear at sea surface under high wind speed. In the present paper, a parameterization of sea surface aerodynamic roughness has been proposed, which is applicable to various wind speeds with involvement of the impact of sea spray. The COARE3.0 model has been improved by introducing the proposed roughness parameterization into the model, so that it could be applicable to the condition with wind speeds higher than 20m/s. With the observational data obtained from buoys located in South China Sea, the improved COARE3.0 model is applied to compute air-sea heat flux. The impact of sea spray on air-sea heat flux is investigated. It is indicated that the sensible heat flux and latent heat flux are mainly determined by air-sea temperature difference and air-sea humidity difference, with very weak relevance to wave age, and the impact of sea spray on heat flux is trivial, for wind speeds of 0~20m/s, while for wind speeds higher than 20m/s, their relevance to air-sea temperature difference and air-sea humidity difference is decreasing and the relevance to wave age is increasing, and latent heat flux is correlated negatively with wave age. As the impact of sea spray is considered, the total heat flux is increased considerably, the sensible heat flux increase due to sea spray is averagely 38.89% of the interface sensible heat flux and the latent increase due to sea spray is averagely 39.19% of the interface latent heat flux.In this study, the seasonal distribution of wind wave events is analyzed to investigate the relationship between wind wave condition and air-sea heat flux. It is found that the wind waves prevails in winter, and reaches its minimum in summer ; the sensible heat flux shows similar seasonal variations with the wind wave events , while the latent heat flux dominates in both winter and summer. The correlation coefficient between wind wave condition and sensible heat flux is 0.67.