ATMOSPHERIC WATER-VAPOR CHARACTERISTICS AT 70-DEGREES-N

Using an extensive rawinsonde archive, characteristics of Arctic water vapor and its transports at 70 degrees N are examined for the period 1974-1991. Monthly-mean profiles and vertically integrated values of s pecific humidity and meridional vapor fluxes are computed for land sta tions north of 65 degrees N for the surface up to 300 mb using once to twice dairy soundings. Mean values at 70 degrees N for these and othe r variables, including temperature and meridional winds, are obtained through an objective analysis of the monthly station means. The annual zonal mean specific humidity at 70 degrees N ranges from 2.4 g kg(-1) at the surface to 0.02 g kg(-1) at 300 mb. Zonal-mean precipitable wa ter ranges from 2.9 mm in February and March to 16.2 mm in July. For a ll months, over 95% of water vapor is found below 500 mb. Although mea n winds are equatorward up to about 400 mb, the tendency for poleward winds to transport more water vapor results in a poleward annual-mean flux at all levels except at the surface, peaking at 1.5 g kg(-1) m s( -1) at 850 mb. Whereas over 85% of the integrated zonal-mean meridiona l flux is found below 500 mb for all months, a smaller percentage is f ound at lower levels during summer due to stronger equatorward winds. The Bur convergence across 70 degrees N is positive in all months, pea king in September at an equivalent monthly water depth of 22.1 mm aver aged over the region north of 70 degrees N. Aerological estimates of p recipitation minus evaporation (P - E) for the area north of 70 degree s N that account for changes in water storage also peak in September ( 26.1 mm), with the annual total of 163 mm larger than previous estimat es by up to 36%. Integrated vapor transports exhibit marked longitudin al variations, with maximum annual poleward transports of 16-25 kg s(- 1) m(-1) found over the Norwegian Sea and Baffin Bay. The Canadian Arc tic archipelago is the only sector where mean integrated transports ar e equatorward, ranging from 1 to 10 kg s(-1) m(-1) depending on longit ude. The September peak in P - E results from a circulation shift yiel ding poleward fluxes along a broad zone from near the prime meridian t o 150 degrees E.