http://journals.cambridge.org Downloaded: 11 Dec 2013 IP address: 221.181.192.30 Antarctic Science 8 zyxwvuts (2): 209-21 7 (1996) zyxwvut Atmospheric surface pressure over the interior of Antarctica UWE RADOKl, IAN ALLISON? and GERD WENDLER8 UZES, zyxwvutsrqp Campus Box 449, University of Colorado, Boulder, CO 80309, USA ZAntarctic CRC and Australian Antarctic Divkwn, GPO Bar 252C, Hobart 7001, Australia 3GeophysicalInstitute, University of Alaska, Fairbanks, AK 99775-0800, USA zyx Abstract: zyxwvutsrq Atmospheric surface pressures zyxwvu on the East Antarctic ice sheet are examined as a contribution to a new regional climatology based on automatic weather stations (AWS). Monthly mean pressures along two meridional AWS lines show near the coast a semi-annual oscillation with equinoctial minima, which become submerged inland under a larger annual oscillation, asymmetrically shaped around a summer solstice peak. Such a peak could arise when air surrounding the ice sheet is heated and enabled to spread out over the ice. This concept has provided a classical prediction of the ice sheet’s mean elevation; in this paper the theory is expressed in a more modern form. After the summer “flood” the vertical tropospheric circulation driving the progressive katabatic surface layer drainage from the ice sheet should create relatively higher pressures below the convergence region over the ice sheet center and lower pressures near the coast. In fact the observed mean monthly surface pressures decrease with elevation more slowly than follows from substituting the observed mean temperature-elevation gradients (“topographical lapse rates”) in the hydrostatic equation. However, below the surface inversion along the sloping ice sheet surface the hydrostaticbalance is shown to be governed by temperatures higher than observed at the surface. Hydrostatic pressures are calculated with climatic estimates of the inversion strength. Their differences from the observed monthly mean surface pressures represent non-hydrostatic residuals which can be added to pressures at the coast to form elevation-free (“sea level”) pressure profiles. These show both the expected coastal troughs and high pressure over an ice sheet summit (Dome C). Received 14 December 1995, accepted 3 January 1996 Key words: automatic weather stations, climatology, East Antarctica, ice sheet Introduction The establishment on the East Antarctic ice sheet of an automatic weather station (AWS) network (Allison zyxwvu & Morrksy 1983, Wendler et al. 1986) has made possible a regionalsurfaceclimatologyof the Antarctic interior (AUison etal. 1993). In this paper we use data from two lines of AWS, the IAGO (Interaction atmosphtre-glace-oc6an) line (extending from Dumont d’Urville to Dome C) and the ANARE (Australian National Antarctic Research Expeditions) line (extending from Casey toward Vostok), to examinethe pressuresand to investigate relationshipsbetween elevation, temperature, and surface pressure along the ice sheet surface. The locations of the AWS are given in Fig. 1 and Table I. Elevations in Table I generally represent satellite geodetic data (Transit or Global Positioning System (GPS)), corrected to orthometric heights with a broad-scale field of geoid- ellipsoid separation. The first AWS started operating in 1980, and observations up to and including those for 1990 have been available for this work. However, in some of the discussionsbelow, the relatively completeAWS observations for the single year 1987 (omitting dubious data from GC46) will be used in order to reduce differences that could be introduced by station records of different lengths. Fig. 1. The automatic weather stations (AWS) of the IAGO line, extending from Dumont d’Urville to Dome C, and of the zy ANARE line, extending from Casey to GC 46. 209