LAND PROCESSES IN CLIMATE MODELS

This article reviews conceptually the current state of inclusion of land surface processes in climate models and requirements for further observations The atmospheric component of the climate model provides inputs of precipitation and incident surface radiation. Atmospheric model parameterizations of moist convection and the planetary boundary layer (PBL) provide important links to land surface sensible and latent fluxes. The land surface parameterizations provide albedos to determine solar absorption, various resistances to fluxes of heat and moisture from canopy and soil, descriptions of various welter reservoirs, and mechanisms for water to be lost to runoff These parameterizations consist of the algorithms for these processes and the numerical parameter values required by those algorithms. A wide variety of heterogeneities affect fluxes between land surfaces and the atmosphere and occur on scales that are small compared to the spatial resolution of global climate models. These heterogeneities need to be accounted for in terms of statistical distributions and/or relatively fine spatial resolution for specification of land properties. Representation of land properties on a spatial scale of 25-50 km (0.5 degrees) should be adequate for climate modeling requirements over the next decade.