Planetary wave and gravity wave influence on the occurrence of polar stratospheric clouds over Davis Station, Antarctica, seen in lidar and radiosonde observations

Abstract

We present Rayleigh lidar observations of polar stratospheric clouds (PSC) from Davis Station (68.6°S, 78.0°E), Antarctica, from the 2001, 2002, 2003, and 2004 austral winter seasons. The PSC are detected as enhanced backscatter returns at lower stratospheric heights. We use operational radiosonde balloon data to compare the PSC detections with stratospheric temperature and wave properties. As documented by others, we find that the occurrence of PSC is closely tied to average stratospheric temperatures (which, in turn, are closely related to the location of Davis with respect to the Antarctic vortex), with PSC being seen when the temperature falls to near or below the calculated formation temperature of nitric acid trihydrate. There is clear evidence in the sonde data for gravity wave and planetary wave modulation of the stratospheric temperature. We see small-scale wavelike structure in the PSC profiles, which likely arises from gravity waves, but find little direct correlation between a given (vertical) lidar PSC profile and near-contemporaneous sonde profile, probably because the sonde flight is not an instantaneous sounding at the exact spatial location of the lidar. The planetary-wave-induced temperature variations are of the order of 10 times the size of the gravity wave variations and have a greater and more direct influence in PSC occurrence over Davis. Copyright 2006 by the American Geophysical Union.