Trajectories in the Antarctic lower troposphere

The statistics of air mass transport to the Neumayer Antarctic station (8 degrees 22'W, 70 degrees 7'S) are derived from three-dimensional 5-day backward trajectories on the basis of a numerical weather prediction model, the Global Model of the German Weather Service, for the period April 1993 to March 1996. Trajectory errors are discussed in detail and errors of individual trajectories may sum up to from a few hundred to more than a thousand kilometers during 5 days' traveling time despite the high quality of the Global Model and trajectory module described. The most frequent easterly flow at Neumayer consists of advection from oceanic and continental regions. During southeasterly flow, mean trajectories document oceanic air passing coastal continental regions during the 3 days preceding arrival. Air arriving from above the Antarctic continent south of 75 degrees S usually descends over the marginal plateau and especially over the slope region. Advection from the central plateau regions poleward of 80 degrees S is rare. Marine trajectories from latitudes north of 60 degrees S mostly start in 0 - 3 km height. The modeled transport for the arrival levels at 950 hPa and 850 hPa at Neumayer station document that the frequency of oceanic source regions increases with height. Trajectories for 15 other coastal destinations show that near-surface easterly winds with a downslope component dominate along the eastern shore of the Weddell Sea. The prevailing transport from the south at the Filchner Ronne ice shelf arises from deflected barrier winds along the Transantarctic Mountains. At the northern tip of the peninsula, westerly winds prevail, and the air usually originates from the Bellingshausen Sea. The probability of contact with air masses from ice-free continents is small for all coastal sites.