The Daily Behavior of Pressure and Its Influence on the Wind Regime in East Antarctica during the Winters of 1993 and 1994

Abstract

The analysis of surface pressure data obtained in 1993?94 at the Dumont d'Urville meteorological station and at Automatic Weather Stations Dome C, D-47, and D-80 (East Antarctica) shows the existence of a daily variation. Power spectra are characterized by the presence of a pronounced 1/2-day peak; a 1-day peak is only slightly evident. However, the magnitude of the spectral density at 1 day is about 4?6 times higher than that of 1/2 day. This behavior is different from that observed at lower latitudes, at which two pronounced peaks at 1 and 1/2 day, of similar magnitude, are observed. The yearly averaged daily pressure time series show two maxima, one at 0900 LT and the other at 2100 LT. The magnitude of this variation increases toward the coast, that is, varying from 0.25 hPa at Dome C to 0.4?0.6 hPa at Dumont d'Urville. The difference of the daily pressure behavior at individual sites produces a daily variation in the quasi-meridional pressure gradient between different pairs of stations. This quasi-meridional gradient likely is one of the mechanisms conditioning the daily wind behavior at the near-coastal zones, especially during the winter, when the daily variation of the buoyancy difference between inland and coastal zones is weak. The analysis of the wind velocity daily cycle for different seasons shows that its behavior in winter differs from both the summer and midseason counterparts. In winter, the maximum meridional wind component at Dumont d'Urville is correlated well with the maximum of the pressure gradient. This pressure gradient should be taken into account in modeling the wind regime over Antarctica during winter, when the buoyancy gradient daily variation is negligible.