LAND PROCESSES IN CLIMATE MODELS

This article reviews conceptually the current state of inclusion of la nd surface processes in climate models and requirements for further ob servations The atmospheric component of the climate model provides inp uts of precipitation and incident surface radiation. Atmospheric model parameterizations of moist convection and the planetary boundary laye r (PBL) provide important links to land surface sensible and latent fl uxes. The land surface parameterizations provide albedos to determine solar absorption, various resistances to fluxes of heat and moisture f rom canopy and soil, descriptions of various welter reservoirs, and me chanisms for water to be lost to runoff These parameterizations consis t of the algorithms for these processes and the numerical parameter va lues required by those algorithms. A wide variety of heterogeneities a ffect fluxes between land surfaces and the atmosphere and occur on sca les that are small compared to the spatial resolution of global climat e models. These heterogeneities need to be accounted for in terms of s tatistical distributions and/or relatively fine spatial resolution for specification of land properties. Representation of land properties o n a spatial scale of 25-50 km (0.5 degrees) should be adequate for cli mate modeling requirements over the next decade.