Abstract: A model of atmospheric boundary layer was used to estimate CT2 over sea. The input parameters are air temperature,sea surface temperature and wind speed. A reasonable good agreement between the model predictions and the measurements of CT2 over the East China Sea can be found. A detailed sensitivity analysis of the estimation procedure has been made,showing that the accuracy of the CT2 estimate is dependent on the accuracy of the temperature measurement, and the V. Thiermann expression is better than Wyngaard's.