Numerical-thermodynamical prediction of mean monthly ocean temperatures

Abstract

Results are presented of numerical predictions of month-to-month changes in ocean surface temperature anomalies in the Northern Hemisphere, using a thermodynamic model. For the 73-month period December 1965 to December 1970, and June 1972 to May 1973, statistical evaluation of the predictions (of the sign of the change of anomalies) shows skill substantially higher than that of predictions of a return toward normal. The effect of the different heating and transport components that enter in the predictions is evaluated. It is shown that the horizontal turbulent transport of heat in the oceans corresponding to an exchange coefficient equal to 3 × 108 cm² sec⁻¹ plays an important role in determining the skill of the predictions. However, a model in which the total horizontal transport of heat is neglected also shows good skill, due to evaporation and vertical turbulent transport of sensible heat from the surface of the oceans. The anomalies in the transport by mean ocean currents due to anomalies in the surface wind are taken into account using Ekman's formulas. However, although they are important for the changes of the temperature anomalies, their contribution in improving the skill of the predictions is not apparent from the limited number of cases in which they were included.