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The Land Dynamics (LaD) Model of Land Water and Energy BalanceThe mathematical simulation of processes controlling storage and fluxes of water and energy on land is a fundamental problem of hydrology, with relevance also to ecology, climate dynamics, and several other earth sciences. During the last two decades, dozens of land models have been created by various groups for various purposes. In a recent rigorous test of the most prominent of these models, however, not one was found to predict annual water balance any better than the extremely simple semi-empirical water-balance equation of M. I. Budyko. Such a finding is remarkable, because the models use soil, climate and vegetation data that do not enter the Budyko equation, and so ought to produce superior performance. Recently, Milly and Shmakin (2002a, abstract, paper) introduced the Land Dynamics (LaD) model. The model was tested against observational data for large river basins, with special consideration of the effects of errors in the precipitation data (Milly and Dunne, 2002a, abstract, paper) used to force the model. Milly and Shmakin (2002b, abstract, paper) found that the LaD model successfully outperformed Budyko’s equation. Two applications of the LaD model are (1) its use to generate data for collaborative studies with other earth-science disciplines and (2) its adoption for coupling with atmospheric (GFDL GAMDT, 2004) and climate models at GFDL. For example, the LaD model will be used by GFDL in numerical experiments being conducted for the 4th Assessment Report of the Intergovernmental Panel on Climate Change. |
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U.S. Department of Interior | U.S.
Geological Survey |