Short-term and seasonal variability of the atmospheric water vapor transport through the Mackenzie River basin

The transport of water vapor through the Mackenzie River basin, a typical h igh-latitude river basin, is examined for the years 1979-93, with the Europ ean Centre for Medium-Range Weather Forecasts reanalysis dataset (ERA). It is shown that the transport of water vapor through the Mackenzie basin is h ighly variable in space and time. This transport has two distinct modes. Du ring the autumn, winter, and spring, moisture is transported into the basin from the southwest by extratropical cyclones. The source of this moisture is argued to be the subtropical and midlatitude central Pacific Ocean. Duri ng the summer, moisture enters the basin from the northwest, with the sourc e region being the Arctic Ocean. The values of monthly water vapor budgets obtained with the objectively analyzed fields are compared with those obtai ned from interpolated radiosonde data and with other known quantitative inf ormation about the water budget of the basin. It is found that the ERA data seriously overestimate the values of monthly water budget. A discussion of various potential sources of this discrepancy is provided.