The PIs will continue, and expand upon, their previous modeling studies of the tropical oceans and atmosphere. A major focus will be the development of an improved atmospheric heating parameterization, taking into account the distinct processes operating within and above the boundary layer. This will be aided by existing and planned diagnostic studies based on observed (or analyzed) winds, as well as GCM calculations. Their Pacific coupled model will be extended to the Atlantic and Indian Ocean sectors, first individually, and finally as a coupled model of the global tropics. This will include parameterizations of land-atmosphere interactions that have thus far been ignored. They will seek to identify the extent and nature of climate variability that arises from local interactions within each oceanic sector, and the manner in which inter-basin interactions modify or enhance that variability. The new parameterizations will be incorporated into a multi- level, global atmospheric model. Both linear and primitive equation versions will be developed. Explicit boundary layer physics will permit a more realistic representation of the actual oceanic forcing, and allow for a relatively inviscid free atmosphere, in contrast to their previous model. Long-term coupled simulations with this model will be used to study the mechanisms of low frequency climate change in the tropics. This research project is important because it will shed more light on the role of the coupling between global oceans and the atmosphere on climate variability.
