Atmospheric model data for macroscale hydrology

Abstract

Conventional climate observation networks are often deficient in both quantity and quality of data for macroscale hydrological modelling. In this sense we regard a basin as macroscale if it exceeds 10 000 km 2. Atmospheric models such as general circulation models (GCM) and numerical weather prediction models (NWP) provide alternative sources of data in such cases. While there are many questions concerning the accuracy of the hydrologically-relevant output from such models, experience has shown good results in hydrological modelling of macroscale northern basins. The spatial scale of climate data used in the hydrological modelling has varied from 3.75° (∼400 km at 60°) for GCM data to 4 km for data from a high resolution boundary layer model. The time periods used have varied from a few days for NWP data to almost a century for data from the high resolution boundary layer model. Comparisons of hydrological model outputs using data from various atmospheric models for the 37 000 km 2 upper Columbia Basin and the 1.8 million km 2 Mackenzie Basin in north-western Canada are given. The experience gained in such one-way off-line coupling of atmospheric and hydrological models will be useful in developing a global model of the full hydrological cycle with two-way linking of atmospheric, oceanic and hydrological models.