Recent numerical-thermodynamic experiments on sea surface temperature prediction

Abstract

The conservation of thermal energy applied to the upper layer of the oceans, is used to predict mean monthly sea surface temperature anomalies in the Northern Hemisphere. As input data we use the sea surface temperature,the 700-mb temperature and the surface air pressure in the previous month, as prepared by NOAA. A study is carried out on the relative importance, for the predictions, of the anomalies of the horizontal transport by wind drift ocean currents, and by horizontal turbulent mixing, as well as the heating by evaporation, sensible heat given off to the atmosphere, and short and long wave radiation. To compute the wind drift ocean currents we use an Ekman model forced with a geostrophic surface wind.Numerical experiments varying the angle between the geostrophic surface wind and the resultant surface current shows that the best predictions are obtained for an angle equal to zero degrees.A verification in the Pacific and Atlantic oceans for the 36-month period from June 1980 to May 1983 shows some degree of skill in the predictions due to the heating and the turbulent mixing terms. However, the best skill is obtained when, besides these terms, the anomalies of the transport by wind drift ocean currents are included in the predictions. The skill is still substantially increased when, for computing the wind drift ocean currents and the heating, we use- the prescribed geostrophic wind and the 700-mb temperature for the current month, instead of the ones for the previous month. These semiprediction experiments show that a more complete model in which the Surface gcostrophic wind and the air temperature arc predicted, will lead to a considerable improvement in the predictions.