The distribution and transport of atmospheric water vapour over the Arctic Basin

Abstract

AbstractA comprehensive rawinsonde archive, comprising atmospheric soundings from fixed stations, ships, and the former Soviet Union ‘North Pole’ series of drifting ice stations, is used to examine features of the distribution and transport of Arctic water vapour. Results are based on analysis of climatological, gridded seasonal and monthly fields north of 65°N of precipitable water, vertically integrated vapour fluxes, and profiles of specific humidity, vapour fluxes, temperature, and winds, compiled from objective interpolation of the quality controlled soundings. Emphasis is placed on contrasting conditions for winter and summer, with due attention paid to the potential effects of uncertainties in the rawinsonde humidity data.For zonal means, specific humidity for all seasons typically displays a surface maximum, decreasing poleward at all levels. Precipitable water (surface‐300 hPa), has winter values ranging from 3.8 mm for 65°−70°N and 1.8 mm for 80°–90°N, with annual maxima in July of 18.2 and 12.5 mm, respectively. These zonal means, however, mask large spatial variations; precipitable water for winter, spring, and autumn shows a marked equatorward increase towards the Atlantic side of the Arctic only. Minima are found over north‐east Canada during spring, summer, and autumn.Vapour fluxes tend to peak in the lower troposphere at about 850 hPa in winter, but over a broader layer in summer. During winter, the largest vertically integrated (surface‐300 hPa) zonal and meridional vapour transports are found between Iceland and Scandinavia. The Beaufort Sea and western Canada are the only regions where vertically integrated meridional fluxes are equatorward. During summer, the vertically integrated total flux (zonal plus meridional components) increases sharply over the Beaufort Sea. Equatorward meridional fluxes are again found over western Canada, with strong poleward meridional transports over the Atlantic sector.