Global Land-Atmosphere Coupling Experiment (GLACE)

Randy Koster (

In numerical atmospheric models, the degree to which the atmosphere responds to anomalies in land surface state (the "coupling strength") is a net result of complex interactions between numerous complex process parameterizations, such as those for evapotranspiration, boundary layer development, and moist convection. The great majority of AGCM land-atmosphere interaction studies appear to take a given model's implicit coupling strength on faith, not addressing either its realism or how it compares with that in other models. This is arguably a major deficiency in the current state of the science. The goal of GLACE is to quantify and document the coupling strength across a broad range of AGCMs. The project will not be able to address the realism of simulated coupling strength, since direct measurements of land-atmosphere interaction at large scales are not available. It will, however, show the extent to which coupling strength varies between models, and it will allow individual models to be characterized as having a relatively strong, intermediate, or weak coupling, for later use in interpreting various results (e.g., land use change studies, precipitation feedback studies) obtained with those models.

Koster, R. D., P. A. Dirmeyer, A. N. Hahmann, R. Ijpelaar, L. Tyahla, P. Cox, and M. J. Suarez, 2002: Comparing the degree of land-atmosphere interaction in four atmospheric general circulation models. J. Hydromet., 3, 363-375.

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Updated 11/3/03