Streamflow simulations for continental-scale river basins in a global atmospheric general circulation model

Streamflow simulations for 23 major river basins from the third-generation general circulation model (GCM) of the Canadian Centre for Climate Modellin g and Analysis are assessed. Precipitation and runoff data are used from th e AMIP II simulation in which the GCM is integrated for a 17-yr period with specific sea surface temperatures and sea-ice concentrations. Compared to the observations, the components of the global hydrological cycle and, the globally averaged precipitation and runoff over land, are well simulated. T here remain, however, discrepancies in the simulation of regional precipita tion and consequently runoff amounts, which lead to differences in basin-wi de averaged quantities. Mean annual model precipitation is within 20% of th e observed estimates for 13 out of 23 river basins considered. Model mean a nnual runoff is within 20% of the observed estimates for only 4 out of thes e 13 river basins. Analysis of basin-wide averaged monthly precipitation an d streamflow data, and the errors associated with the mean, and amplitude a nd phase of the annual cycles, indicate that model streamflow simulations i mprove with improvement in GCM precipitation. (C) 2001 Elsevier Science Ltd . All rights reserved.