The role of convection in the global energy cycle

The atmospheric energy cycle according to Lorenz is a classical way to describe the global heat budget. It is based on the concept of available potential energy. This involves (i) the generation of available potential energy due to radiative and condensational heating and (id) the transfer between the global reservoirs of available potential and kinetic energy. The energy transfers (i) and (id) happen not only on scales resolvable by the observational network (gridscale) but also on smaller scales (sub - gridscale, controlled by convection). However, only the gridscale components have been evaluated in the pest. In the project P9387-GEO entitled "Diagnostic estimate of the global diabatic heating", we have applied, for the first time, a method that yields also the sub-gridcale components. This has become possible by an indirect diagnostic technique, developed recently by our group. Together with the high-quality global analyses of the European Centre for Medium-Range Weather Forecasts we have found for the transfer rate (id) that its sub-gridscale part is about as large as the classical gridscale part. This suggests that the efficiency of the global atmosphere as a heat engine is about twice as high as previously estimated. This is a relevant, and new, result. However, it is based upon data for just one month. Our preliminary estimates need to be checked with longer-term averages over several years. Further, it appears desirable to implement the high-quality radiative heating plus output from the 1992/93 tropical Pacific experiment (TOGA-COARE); the corresponding data sets have never been available before. It is proposed to continue the present project (which will run out in June 1996) for a final period of 1.5 years. Funds are required for a postdoctoral fellow and an undergraduate student (18 months each) plus travel plus limited computer equipment. The total financial volume would be 1.12 Mio ATS. Since the voluminous numerical evaluations of the radiative heating can only be made at ECMWF, Reading, U.K., the travel money (about 7 o of the total) is absolutely essential. Without it the project cannot be successful.