The World Climate Research Programme's Global Energy and Water Cycle Experiment (GEWEX) addresses both the hydrological and meteorological components of the water cycle. One of the biggest challenges in GEWEX is to improve the understanding of how the wide range of processes within clouds affects the atmosphere on the large scale and, thereby, to develop ways of parameterizing these processes within climate and NWP models. The Joint Scientific Committee of WCRP at its 1992 meeting approved the establishment of a GEWEX Cloud System Study (GCSS) as a long-term program that will address these issues mainly through the development of cloud-resolving models and their use to generate realizations of a set of archetypal cloud systems. The focus of GCSS is on cloud systems spanning the mesoscale rather than on individual clouds. Observations from field programs will be used to develop and validate the cloud-resolving models, which in turn will be used as test-beds to develop the parameterizations for the largescale models. The cloud-resolving models provide synthetic datasets representing rather complete descriptions of entire cloud systems, from which it will also be possible to develop algorithms for remote-sensing observations.
*The chairman of the GEWEX Cloud System Science Team, K. A. Browning, was assisted in the preparation of this report by A. Betts, P. R. Jonas, R. Kershaw, M. Manton, P. J. Mason, M. Miller, M. W. Moncrieff, H. Sundqvist, W. K. Tao, and M. Tiedtke (all of whom participated in workshop sessions held in Reading, United Kingdom, in 1991), and P. V. Hobbs, J. Mitchell, E. Raschke, R. E. Stewart, and J. Simpson (who contributed by correspondence).