Assessment of simulated water balance for continental-scale river basins in an AMIP 2 simulation

Streamflow, which integrates the response of the land surface to atmospheri c forcing over large areas, is a useful diagnostic to assess the performanc e of land surface schemes over large spatial scales. This paper uses observ ed runoff and streamflow data to assess the performance of the Canadian lan d surface parameterization scheme (CLASS), when operated within the Canadia n Centre for Climate modeling and analysis (CCCma) general circulation mode l (GCM) at 3.75 degrees resolution, for three continental-scale river basin s. Estimates of evapotranspiration obtained using atmospheric water balance , and soil moisture obtained using the VIC-2L model, are also used to asses s the CLASS water balance simulations. Comparisons with observations of str eamflow, and estimates of evapotranspiration and soil moisture, suggest tha t although CLASS simulates the annual cycle of evapotranspiration, streamfl ow, and soil moisture reasonably well, it overestimates evapotranspiration, underestimates runoff, and simulates slightly wetter soil moisture conditi ons.