Comparison between wind blocking fields and propagating directions of mesospheric gravity waves observed from all-sky imagers over King Sejong Staion, Antarctica

Abstract

We analyzed mesospheric gravity waves in OH airglow images observed during 2012-2016 by an all-sky camera at King Sejong Station (KSS; 62°S, 58°W), Antarctica. Using a new method of 2D image analysis recently developed by Matsuda et al. (2014), we obtained power spectra of horizontal phase velocity from the image sequence of total 107 image windows. We found from total power spectrum density thatwave activity is maximized during winter, as is previously known. We also derived wind blocking fields from MERRA2 reanalysis datafor the altitudes 10 -64 km and from KSS meteor radar data for 80 -90 km. By comparing the dominant propagating direction of short period gravity waves with the wind blocking field, we found a significant anti-correlation between wind blocking fields and dominant propagating direction of gravity waves except fall season, indicating wind filtering effects. The finding is the direct evidence of wind filtering effects observed in the mesosphere for the first time. During fall, the wind blocking fields below ~40 km are not matched with the dominant propagating directions. Thus, we suggest that mesospheric gravity waves observed by the all-sky camera during fall were generated above ~40 km (upper stratosphere and lower mesosphere), probably due to secondary waves. This exception will open up theoretical questions in middle atmosphere dynamic research area.