Land surface processes in climate models

Chapter summary Much of our understanding of how land surface processes and vegetation affect weather and climate comes from numerical models of surface energy fluxes and the hydrologic cycle coupled to atmospheric numerical models. Land surface models are coupled to atmospheric numerical models to simulate the absorption of radiation at the land surface, the exchanges of sensible and latent heat between land and atmosphere, storage of heat in soil, and the frictional drag of vegetation and other surface elements on wind. These models of land surface processes were initially developed to provide the surface boundary conditions of radiative and turbulent fluxes required by atmospheric numerical models. They have since evolved to simulate the hydrologic cycle, biogeochemical cycles, and vegetation dynamics so that the land and atmosphere are represented as a coupled system. This chapter reviews the historical development of land surface models, particularly the parameterization of processes, the inclusion of satellite data in the models, and the representation of heterogeneity in the landscape. Model validation is discussed, as well as application of the models in climate model experiments. Hydrometeorological models Global climate models represent a set of numerical equations that describe the large-scale circulation of the atmosphere and ocean and their physical state, including interactions among oceans, atmosphere, land, and sea ice that affect climate (Trenberth 1992; McGuffie and Henderson-Sellers 2001, 2005; Washington and Parkinson 2005; Randall et al . 2007).