Variability of the Arctic atmospheric moisture budget derived from TOVS satellite data

Temporal and spatial variability of the Arctic atmospheric moisture budget is investigated using a new 19-year data set (1980 to 1998) produced from daily precipitable water retrieved from the TIROS Operational Vertical Sounder (TOVS) and upper-level winds from the NCEP-NCAR Reanalysis [Groves and Francis, 2002]. Seasonal differences in moisture transport arise from distinct winter/summer circulation regimes and meridional moisture gradients. In winter approximately 80% of the net precipitation (precipitation minus evaporation) is transported along well-defined storm tracks. Summer P-E is double that of winter and dominates the annual pattern. Decadal differences in winter P-E reveal statistically significant increases in the Beaufort and eastern Greenland-Iceland-Norwegian Seas, decreases in the Canadian Archipelago (islands in far northeast Canada) and Kara Sea, and a slight increase in the Arctic as a whole. Annual differences are dominated by winter changes.

When the phase of the Arctic Oscillation (AO) index is positive, the net PW flux across 70 deg. ?N in winter is 6 times larger than on negative-index days. Over the entire Arctic, P-E is 29% larger (20% lower) than the average on days with a positive (negative) AO index. In summer the PW transport is twice as large and P-E is 27% higher on positive versus negative AO days. These results suggest that if the AO continues its trend toward a predominantly positive phase, we should expect to observe increasing precipitation in the Arctic overall, and particularly in regions adjacent to the marginal ice zones.