日本地球惑星科学連合2018年大会

講演情報

[EE] Eveningポスター発表

セッション記号 P (宇宙惑星科学) » P-EM 太陽地球系科学・宇宙電磁気学・宇宙環境

[P-EM10] Coupling Processes in the Atmosphere-Ionosphere System

2018年5月22日(火) 17:15 〜 18:30 ポスター会場 (幕張メッセ国際展示場 7ホール)

コンビーナ:Liu Huixin(九州大学理学研究院地球惑星科学専攻 九州大学宙空環境研究センター)、Chang Loren(Institute of Space Science, National Central University)、大塚 雄一(名古屋大学宇宙地球環境研究所)

[PEM10-P11] Different propagation characteristics of gravity waves in the mesosphere and lower thermosphere over Syowa and Davis, the Antarctic, using OH airglow imagers and MF radars

*Masaru Kogure1,2Takuji Nakamura2,1Yoshihiro Tomikawa2,1Mitsumu K. Ejiri2,1Takanori Nishiyama2,1Masaki Tsutsumi2,1Michael J. Taylor3Yucheng Zhao3P.-Dominique Pautet3Damian Murphy4 (1.総合研究大学院大学複合科学研究科、2.国立極地研究所、3.ユタ州立大学物理学科、4.オーストラリア南極局)

キーワード:MLT, Imager, Rader, Gravity wave, Spectral analysis, The Antarctic

Gravity waves transport momentum and energy from the lower atmosphere to the upper atmosphere, and drive the general circulation, which significantly change the temperature in the middle atmosphere [Fritts and Alexander, 2003]. Understanding this role quantitatively will improve the modern general circulation models.

The polar night jet region is known to contain regions of the high gravity wave activity. However, their source, propagation and intermittency are only poorly understood because of a lack of observations. To understand their source and propagation, our group has observed the gravity waves over Syowa (69°S, 40°E) using some instruments (e.g., lidar, OH imager and MF radar). We also compared the gravity waves over Syowa and Davis (69°S, 79°E), at which terrain and meteorological conditions are similar, to investigate their horizontal variation over the east Antarctic. We found, from the lidar temperature observations, that the vertical profile of gravity wave potential energy is similar between Syowa and Davis, except for a clear enhancement around 30-40 km over Davis [Kogure et al., 2017]. Horizontal propagation characteristics are more clearly observed by airglow imaging measurements of ~90 km altitude. The comparison of four imagers' results between April-May 2013 have indicated that the major propagation directions were west ward at three station (Syowa, McMurdo, Halley), but at Davis GWs seems to propagate all the directions, which is totaly different from the other three. [Matsuda et al., 2017]. It seems like the GWs over Davis did not experience the same wind filtering in the middle atmosphere.



The goal of this study is to compare the gravity waves over Syowa and Davis in many different ways and with more observational data. In this presentation, we will show the ground-based horizontal phase speed spectrum over the two stations derived from OH imagers in more details. We analyzed the OH airglow imager data obtaind for eight months (from March to October in 2016) over the two stations with M-transform [Matsuda et al., 2014]. We analyzed the data without clouds and aurora contaminations continuously for at least one hour. The numbers of nights with such data sets are 40 at Syowa and 55 at Davis. The seasonal variations of the nightly mean variance were very similar with winter maximum, but the variance over Syowa was significantly larger than that over Davis in September. The reason for a larger variance over Syowa in September was the existence of southward propagating gravity waves with the phase speed of ~10 - 80 m/s. In 2016, clear sky and aurora free data were available at both station on ten nights. Comparison of phase velocity spectra obtained on the same night showed similarity on at only one night out of ten nights. On five nights, the spectra were quite different. On the other four nights, the spectral peaks with slow westward phase velocity (> 50 m/s) were commonly observed but additional spectral peaks were found over Davis and not over Syowa. We will present comparisons of kinetic energy and propagation direction of gravity waves derived from MF radars, and compare with the results from OH imagers.