Snowfall in high southern latitudes

Abstract

Precipitation over Antarctica is an important climatic variable whose study has been limited by the frequent inability to discriminate between actual snow precipitation and drifting snow. Recent advances in point precipitation measurements promise to circumvent this problem. In addition, indirect estimates based upon t(h)•e atmospheric water balance equation provide seasonal precipitation amounts for areas larger than I xl km 2 . For broad-scale studies in the continental interior net snow accumulation closely approximates precipitation. Annual precipitation is relatively high over the marginal ice slopes in relation to amounts in the interior. This meridional distribution is due to the orographic lifting of moist air by the ice sheet. Zonal precipitation variations are related to the quasi-stationary cyclones in the circumpolar low-pressure trough. Most precipitation falls in winter, when the average moisture content of the air is low. The intensity of cyclonic activity is the key factor governing the amount of precipitation and its variations. Precipitation generation in coastal regions is strongly influenced by the fact that poleward moving, moist maritime air masses are deflected by the steep marginal ice slopes to blow parallel to the terrain contours. Direct orographic lifting with accompanying adiabatic cooling is the dominant precipitation formation mechanism inland of the l-kin elevation contour; intrusions of moist air far into the continent are accompanied by southerly winds through a deep tropospheric layer. Above 3000 m elevation where terrain slopes are gentle, radiative cooling is the primary mechanism by which saturation is maintained within moist air, and thus by which precipitation is formed. Most precipitation at these elevations falls from clear skies. This phenomenon does not differ from precipitation originating in clouds but is a direct result of the low moisture content of the air, and hence ice layers are optically too thin to be visible as clouds.

Atmospheric signals and characteristics of accumulation in Dronning Maud Land, Antarctica

“…For the highestprecipitation amounts, there are links to the occurrence of blocking and related amplification of long planetary waves. This feature was also noted by Bromwich [1988] to play an important role for Antarctic precipitation in general. The associated strong upper level advection brings moisture and higher temperatures during the events.…”

“…This would not affect the accumulation amount for a given region (i.e.., sublimation and precipitation of the same water), but various chemical constituents could be altered. Bromwich [1988] shows the annual cycle of accumulation at coastal stations in East Antarctica to have a maximum in the winter months of April to September, and stations in the Ross and Weddell Seas tend to have a peak during March. The inland stations exhibit a annual cycle with a maximum in winter.…”

“…Subsequently, it is likely that the accumulation record and the (second order) trace record is affected by ENSO. Bromwich [1988] provides an overview of precipitation for the Antarctic continent and gives a succinct description of two mechanisms for precipitation. Coastal precipitation associated with storms is complicated by orographically induced low-level blocking.…”

Spatial variability of climate and past atmospheric circulation patterns from central West Antarctic glaciochemistry

“…This warm air brings higher concentrations of marine aerosols and a significant amount of the moisture transported to this region [Bromwich, 1988;Hogan, 1997].…”

Variability of precipitation over the coastal western Antarctic Peninsula from synoptic observations

“…These maps indicate that the greatest accumulation is in the coastal region with a rapid decrease toward the interior, suggesting the importance of synoptic-scale weather systems that do not generally penetrate far onto the continent [Bromwich, 1988]. It is also possible to use the output of numerical models to compute the net precipitation (precipitation minus sublimation/evaporation) for the Antarctic, which allows the investigation of precipitation variability across a large area [Brornwich et al, 1995].…”