ATMOSPHERIC CONTRIBUTION TO HYDROLOGIC VARIATIONS IN THE ARCTIC

High-latitude rawinsonde data for 18 years (1973-1990) are used to com pute the atmospheric moisture flux convergence over two regions: the A rctic Ocean and the Mackenzie River drainage basin. The primary object ives are to assess the interannual variability and to compare the macr oscale hydrologic regimes of the two regions. The moisture flux conver gence is positive in all months over the Arctic Ocean, but is occasion ally negative during summer over the Mackenzie Basin. The climatologic al seasonal cycle of the moisture convergence contains a late-summer ( August-September) maximum over the Arctic Ocean but a late-summer mini mum over the Mackenzie Basin. Evaporation, deduced from the moisture i nflow and independent data on precipitation, makes a much greater cont ribution to the atmospheric moisture budget of the Mackenzie domain, e specially during summer. The respective equivalent area averages of th e 18-year annual mean moisture flux convergence, precipitation and der ived evaporation are 17.3, 19.5 and 2.2 cm a-1 for the Arctic Ocean an d 24.9, 33.6 and 8.7 cm a-1 for the Mackenzie domain. However, the ran ge of interannual variations of the flux convergence is about +/-50% o f the annual means and more than twice the monthly means. The annual t otals of the flux convergence are correlated with station-derived prec ipitation over the Mackenzie domain and with yearly variations of the Mackenzie discharge. The moisture flux convergence over the Mackenzie domain suggests that station reports underestimate precipitation durin g the winter months by amounts equivalent to several centimetres per a nnum.