Latent heat flux and interannual variability of the coupled atmosphere-ocean system

Abstract

This study examines the impact of the moisture exchange between the oceanic and atmospheric boundary layers on instabilities of the atmosphere-ocean system. Wind speed-sensitive evaporation can affect these instabilities in two ways. First, it can change atmospheric heating and thus modify the atmospheric wind response. Second, it can change the mixed layer heat budget and thus affect SST. Here the authors show that wind speed-sensitive evaporation produces a new unstable, westward-propagating SST mode with a growth rate of (4 month)-1 for standard parameters. These two processes, alternatively, act to stabilize the leading unstable mixed SST-dynamics mode if each is considered separately. However, the strongest instability of this mixed SST-dynamics mode occurs when the first process is relatively weak and the second is strong. The authors extend the work to consider the impact of wind speed-sensitive evaporation on the intermediate coupled model of Zebiak and Cane. The results from this model are similar to those obtained in the free mode analysis.