Spatial and temporal structure of atmospheric water vapor transport in theMackenzie River basin

The transport of water vapor through the Mackenzie River basin, a typical h igh-latitude river basin, is examined for the period from August to October 1994. The spatial and temporal variability in the transport is considered with both objectively analyzed fields and radiosonde data. Previous studies of the high-latitude water vapor have made use of radioson de data and have been able to document some features of annual cycle of wat er vapor transport. These studies have left unresolved many important aspec ts of moisture transport processes. In particular, detailed information as to the spatial and temporal variation of the transport has not been fully d ocumented or understood. In order to address these important issues, the au thors make use of the objectively analyzed fields from the European Centre for Medium-Range Weather Forecasts to study the high-latitude transport of water vapor. This paper presents findings regarding the transport of water vapor over northern parts of North America. It is shown that the transport is highly variable in time with transient synoptic-scale disturbances being responsible for much of the transport. The prospect of using the objective ly analyzed fields to determine the spatial structure of humidity fluxes an d the evaporation-precipitation field in data-sparse high-latitude regions is discussed. The results obtained with the objectively analyzed fields are compared with those obtained directly from radiosonde data for stations in and around the basin. The influence that the local land topography has on the regional water vapor balance is also discussed.