87th AMS Annual Meeting

Monday, 15 January 2007: 1:30 PM
GEWEX Water and Energy Budget Studies
209 (Henry B. Gonzalez Convention Center)
John Roads, SIO/Univ. of California, La Jolla, CA
During the past several years, the Global Energy and Water-Cycle Experiment (GEWEX) Continental Scale Experiments (CSEs) began an attempt to develop the “best available” description of global and regional atmospheric and land water and energy budgets. Since few regional or global hydrometeorological observations were available when these water and energy budget studies began, initial studies mainly included global and regional atmospheric analyses along with macroscale hydrologic models. Fortunately, a number of observationally based GEWEX data sets have since become available and include: the Global Precipitation Climatology Project (GPCP) precipitation, International Satellite Climate Comparison Project (ISCCP) and Surface Radiation Budget (SRB) radiation, the Global Runoff Data Center (GRDC) runoff. Other globally gridded observations sets are also now available. We have therefore begun to compare the National Centers for Environmental Prediction / National Center for Atmospheric Research (NCEP/NCAR), NCEP / Dept. of Energy (DOE), European Centre for Medium Range Forecasts (ERA40), and Japanese Meteorological agency reanalyses, along with the Global Land Data Assimilation and Global Soil Wetness Project output to these observations in order to assess our current uncertainty to characterize and close continental-scale water and energy budgets. As will be shown, the closure errors are not small. Individual process errors in these models, which tend to cancel, are likely much larger. For example, analysis precipitation errors are likely balanced mainly by evaporation errors. Errors in other hydrometeorological processes, such as regional runoff and moisture convergence, are almost as large, especially for certain regions like the Amazon and GAME tropics.

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