Interstation correlation of high-latitude lower-stratosphere gravity wave activity: Evidence for planetary wave modulation of gravity waves over Antarctica

Abstract

Four years of operational radiosonde balloon flights, from three Australian stations in eastern Antarctica (Casey, 66.3°S, 110.0°E; Davis, 68.6°S, 78.0°E; and Mawson, 67.6°S, 62.9°E) are analyzed to derive lower-stratosphere (12–20 km altitude) gravity wave information from perturbations in wind and temperature. Gravity wave activity and seasonal behavior was found to be similar to that seen in earlier studies from Antarctica. Interstation comparisons of zonal wind and gravity wave activity showed very high correlations throughout the entire data set, between Mawson and Davis stations (∼600 km distant), with a lag near 0.5 days. The correlations between Casey and Davis (1400 km apart) were lower but still significant, with a lag near 1 day. There is no significant correlation between stratospheric gravity wave activity and surface winds. Our results suggest a pattern of winds and waves moving eastward over the stations with a speed near 15 m s−1. As this is comparable to planetary wave speeds, we interpret our results as being evidence for a significant planetary wave–induced modulation of the zonal wind and the gravity wave field, although we are unable to identify the mechanism by which this operates. Our work suggests that the high-latitude lower-stratosphere gravity wave fields are relatively uniform on spatial scales of 500–1000 km and on timescales of around 0.5–1 days.