17:15 〜 18:45
[PEM12-P01] Month-to-month variations in the potassium layer during Antarctic winter
キーワード：カリウム層、共鳴散乱ライダー、昭和基地
Metallic layers, containing such as Na, Fe, K, etc., originating from meteors are valuable tracers for observations of the Earth's upper atmosphere. Through investigations on variations in such metallic layers, it would be important to advance our understanding of the dynamical and chemical processes in the upper atmosphere where it is not easy to make observations. Many observations for Na and Fe have been done for decades, and their variations have been widely investigated. On the other hand, observational data on K are relatively limited. As for previous K observations, there are several reports from several resonance scattering lidars located in, such as Arecibo, Puerto Rico (18.35°N, 66.75°W), Beijing, China (40.41°N, 116.01°E), Kühlungsborn, Germany (54.1°N, 11.7°E), which are the observational sites in the Northern Hemisphere. In addition, a shipboard-lidar campaign between 71°S and 45°N was carried out, and it provided limited information on the K layer variations in the Southern Hemisphere. Furthermore, there are investigations based on near-global K data, which were obtained from observations of K resonance scattering of the sunlight by a polar-orbit satellite, Odin/OSIRIS. The satellite observations were limited during the daytime, which means that the obtained data are mainly during summer at high latitudes. Thus, there are fewer K observations in winter high latitudes in the Southern Hemisphere, where there is less sunlight.
In the present work, we have investigated seasonal variations in the K layer over Syowa Station (69.0°S, 39.6°E), Antarctic, based on observational data which were obtained by a resonance scattering lidar. The resonance scattering lidar was installed at Syowa Station in 2017, and it was operated from 2017 to 2018. During the two winter periods, i.e., March to October, K density data of 385 hours were obtained from K D1 (770 nm) observations of 38 nights. The K observations were performed by the one-frequency and three-frequency methods, and thus we made evaluations of the K density data derived from both methods. The evaluated K density data were analyzed to investigate month-to-month variations during the Antarctic winter. As a result, the peak heights of K number density were mostly 85 to 90 km. The K peak density reached a maximum in June-July during wintertime, and its number density was approximately 2×107 m-3. Then, a minimum of the K peak density was observed in September during springtime, and its number density was approximately 2×106 m-3. The observed column density over Syowa Station exhibited a part of semi-annual variation with minima near September and May. The centroid altitude and RMS width in the K layer showed an annual-like variation: the former had a minimum in June, and the latter reached a peak in June. These results from Syowa Station are compared with the previous observations from satellite observations by Odin/OSIRIS and ground-based lidar observations at Arecibo, Beijing, and Kühlungsborn. From the comparisons, it is found that the relative K column density variations over Syowa Station seemed to be consistent with those from the previous observations. The variation of centroid altitude seems to be close to the results from Odin/OSIRIS, while it was different from those from the lidar observations in the Northern Hemisphere. The variation of RMS width over Syowa Station presents the opposite of those from Arecibo, but it agrees with those from Kühlungsborn and Beijing. In the presentation, we will show these results, together with more details in comparisons with the previous K observations, and discuss important factors that may contribute to the observed month-to-month variations during Antarctic winter.
In the present work, we have investigated seasonal variations in the K layer over Syowa Station (69.0°S, 39.6°E), Antarctic, based on observational data which were obtained by a resonance scattering lidar. The resonance scattering lidar was installed at Syowa Station in 2017, and it was operated from 2017 to 2018. During the two winter periods, i.e., March to October, K density data of 385 hours were obtained from K D1 (770 nm) observations of 38 nights. The K observations were performed by the one-frequency and three-frequency methods, and thus we made evaluations of the K density data derived from both methods. The evaluated K density data were analyzed to investigate month-to-month variations during the Antarctic winter. As a result, the peak heights of K number density were mostly 85 to 90 km. The K peak density reached a maximum in June-July during wintertime, and its number density was approximately 2×107 m-3. Then, a minimum of the K peak density was observed in September during springtime, and its number density was approximately 2×106 m-3. The observed column density over Syowa Station exhibited a part of semi-annual variation with minima near September and May. The centroid altitude and RMS width in the K layer showed an annual-like variation: the former had a minimum in June, and the latter reached a peak in June. These results from Syowa Station are compared with the previous observations from satellite observations by Odin/OSIRIS and ground-based lidar observations at Arecibo, Beijing, and Kühlungsborn. From the comparisons, it is found that the relative K column density variations over Syowa Station seemed to be consistent with those from the previous observations. The variation of centroid altitude seems to be close to the results from Odin/OSIRIS, while it was different from those from the lidar observations in the Northern Hemisphere. The variation of RMS width over Syowa Station presents the opposite of those from Arecibo, but it agrees with those from Kühlungsborn and Beijing. In the presentation, we will show these results, together with more details in comparisons with the previous K observations, and discuss important factors that may contribute to the observed month-to-month variations during Antarctic winter.