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178 Modeling of the Global Water Cycle: Numerical Models (General Circulation Models)

Part 15. Global Hydrology

  1. Randal D Koster

Published Online: 15 APR 2006

DOI: 10.1002/0470848944.hsa184

Encyclopedia of Hydrological Sciences

Encyclopedia of Hydrological Sciences

How to Cite

Koster, R. D. 2006. Modeling of the Global Water Cycle: Numerical Models (General Circulation Models). Encyclopedia of Hydrological Sciences. 15:178.

Author Information

  1. NASA/Goddard Space Flight Center, Greenbelt, MD, US

Publication History

  1. Published Online: 15 APR 2006


Atmospheric general circulation models (AGCMs) are powerful tools for exploring climate sensitivity and the global water cycle. The wealth of data provided by an AGCM allows a complete statistical characterization of its water cycle, a far more complete picture than would be allowed from real-world observations. AGCM numerical experiments have been used to isolate the mechanisms that control water cycle variability, illustrate the potential for water cycle prediction, and quantify water cycle changes resulting from human activities. The AGCM fields can also be merged with observations (via data assimilation) to provide the best estimates possible of the true water cycle. Unfortunately, biases in simulated fields resulting from coarse resolution and inadequate physical parameterizations continue to plague AGCMs, forcing climate modelers to temper their faith in the models' results.


  • general circulation model;
  • earth system model;
  • climate model;
  • AGCM