Winter warming-event observed at Dome Fuji Station and synoptic-scale circulation in the Antarctic

Abstract

The atmosphere over the Antarctic interior is usually separated from the outside by circumpolar tight potential vorticity gradients, where surface transient eddies are embedded, at the Dome Fuji Station (77゜S, 40゜E) on the topographical ridge of the East Antarctic ice sheet, an intensive meteorological observation campaign was carried out in 1997, The daily surface air temperature at Dome Fuji Station in the winter was generally around -70゜C, influenced by a ground-based temperature inversion as well as lower temperature in the polar vortex, On the other hand, the air temperature varied with larger amplitude in winter than in summer, The most prominent fluctuation, which was warming to about -30゜C from -70゜C (approximately a 40゜C-warming for only 2 days), occurred in the second half of June (Hirasawa et al., 2000), The warming was accompanied with increments in surface pressure, surface wind speed, and cloud amount, They were induced by warm, moist air advection from outside of the continent, associated with a blocking ridge which was the leading edge of a quasi-stationary Rossby wave, The present research found 18 warming-events in the 1997 winter from April to October, including the one in June above, Most the warming-events were accompanied by increased surface pressure, surface wind speed, and cloud amount, and were associated with synoptic-scale anticyclonic circulations, respectively.