Variations in aerologically derived Arctic precipitation and snowfall

Abstract
Data from a rawinsonde network are used to provide aerological estimates of monthly precipitation minus evaporation (P – E) averaged over the region north of 70° N. Using published climatological estimates of E, area-averaged P is obtained for each month and year as a residual. Using surface temperatures from the rawinsonde network, the fraction of precipitation falling as snow is then estimated. Over the 1974–91 study period, precipitation and snowfall (water equivalent) have annual means of 26.6 and 19.0 cm. respectively. Assuming a representative aged snowpack density of 330 kg m−3 yields a total snow depth of 57.5 cm. The mean annual cycles of both variables display an autumn maximum, but because of the temperature dependency, nearly all precipitation falls as rain during July and August. Composite analyses reveal that increased precipitation for all seasons and increased snowfall for winter and autumn are favored by a “winter-type” circulation pattern, characterized by stronger troughs over the Atlantic and Eurasian sectors of the Arctic, associated with increased cyclonic activity over the Arctic peripheral seas.