Variability of the Arctic atmospheric moisture budget 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. A companion paper describes the creation and validation of these new moisture budget products [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, P‐E) 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°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.