Intermittency of Gravity Waves in the Antarctic Troposphere and Lower Stratosphere Revealed by the PANSY Radar Observation

Abstract

The momentum fluxes associated with gravity waves (GWs) significantly vary both in time and space. It is important to qualify the intermittency of GWs because the intermittency largely affects the vertical profile of momentum flux convergences in the middle atmosphere. In this study, 1 year of continuous observation with high time/height resolution and accuracy was provided by the PANSY radar, a Mesosphere-Stratosphere-Troposphere (MST) radar at Syowa Station (69.01°S, 39.59°E) in the Antarctic. The PANSY radar is used to study the intermittency of GWs in the troposphere and lower stratosphere. In all seasons, the intermittency is large in the troposphere with Gini coefficients of 0.4–0.6 for absolute momentum fluxes ((Formula presented.)) and 0.4–0.7 for vertical wind variances multiplied by the density ((Formula presented.)). However, the intermittency is small in the lower stratosphere with Gini coefficients of 0.3–0.5 for (Formula presented.) and 0.2–0.4 for (Formula presented.). The seasonal characteristics in the lower stratosphere are different between (Formula presented.) and (Formula presented.) : small Gini coefficients are observed in May–July for (Formula presented.) and in December–February for (Formula presented.). Simple model experiments with ideal distributions of GWs as a function of momentum flux magnitude and ground-based phase velocity are performed. These results indicate that the vertical profiles of the Gini coefficient obtained by the PANSY radar are largely affected by orographic GWs with large amplitudes. The results also suggest that the generation and the partial reflection of GWs play an important role in determining the vertical profile of GW intermittency.