Cool Skin Effect and its Impact on the Computation of the Latent Heat Flux in the South China Sea

The cool skin effect, known as the temperature difference (Delta T) across the skin layer of sea surface, is of vital importance for the accurate computation of the latent heat flux (LHF). The observed features of Delta T in the South China Sea are analyzed using in situ data from a buoy platform over an similar to 6-week period. Only nighttime data are used to exclude the possible warm layer effect. The positive values of Delta T falling into the range of 0-1 K comprise 95% of the data, and the most frequently observed values occur in the range of 0.4-0.6 K (38%). The cool skin model in the Coupled Ocean-Atmosphere Response Experiment 3.0 algorithm is then validated against those observations. The cool skin model has an efficient but insufficient ability to reduce the overestimation of the LHF. The overestimation of the LHF is reduced to 9.5% from 18.0%, leaving nearly half of the biases in the LHF unresolved. The Saunders constant (lambda) in the cool skin model is markedly underestimated, leading to a much weaker prediction of Delta T. A strong linear relationship exists between the mean values of lambda and the LHF with a slope of -0.9 W m(-2). With an approximately doubled lambda, the biases in Delta T and in the LHF could be eliminated. Considering the possible uncertainties in sensors, the value of lambda is estimated as 11.6 +/- 6.7 in the current study.