Hydrological Budgets and Surface Energy Balance of Seven Subbasins of the Mackenzie River from the ECMWF Model

Abstract

The liquid and frozen hydrological budgets and the surface energy budget from seven subbasins of the Mackenzie River are analyzed using hourly integrals from the operational European Centre for Medium-Range Forecasts model from September 1996 to August 1998. The model budgets give estimates of precipitation (rainfall and snowfall), surface evaporation (of water and snow), runoff, and melt terms in the spring. On a basin scale and monthly timescale, the model precipitation correlates well with observations but has a 40% positive bias. On an annual basis, evaporation has a 60% positive bias. Although the annual runoff for the Mackenzie as a whole is close to the annual stream flow, this condition is not true for the subbasins. In the liquid water budget, nudging of soil water compensates for basin errors in runoff. The model snow budget is not closed because each new snow analysis depends heavily on climatological means. The surface energy balance on the basin scale also is analyzed. Although the model gradients of net radiation probably are realistic, the model evaporation bias means that sensible heat flux is negatively biased, especially in spring.