Water Vapor Fluxes over the Saskatchewan River Basin

Abstract

The NCEP?NCAR reanalysis data were used to calculate the atmospheric moisture fluxes into and out of the Saskatchewan River basin for the period 1948?2001. Although bias exists in the estimated moisture flux divergence, the data are still very useful for characterizing the general features of the basin's water vapor fluxes. The direction of the meridional moisture fluxes over the Saskatchewan River basin changes with seasons, but that of the zonal moisture fluxes does not. Moisture flows into the basin from the west (the Pacific Ocean) during all seasons. Moisture influxes from the south in early summer are usually related to the long-distance meridional transport of water vapor from the Gulf of California and the Gulf of Mexico. Moisture flows into the basin from the north in all seasons except for late spring and early summer. The moisture outflow to the east mainly arises from the extensive zonal transport across the basin in all seasons, although this is most pronounced in late summer and autumn. In addition to the two primary moisture sources, the Pacific Ocean and the Gulf of Mexico, the Arctic Ocean is also a moisture source for the Saskatchewan River basin during most seasons. Hudson Bay is another moisture source although this occurs infrequently. Moisture fluxes for the Saskatchewan River basin show some similarities with and differences from those experienced by the Mackenzie River basin. Differences in topography and surface properties between these two basins are key factors generating the differences in water vapor transport. Differences also exist in moisture sources for the two basins. However, there are connections between them through seasonal moisture exchange across the shared boundary.