Statistical Analysis of Polar Mesosphere Summer Echoes with Super Dual Auroral Radar Network

• Main Authors: Hosokawa Keisuke, Ogawa Tadahiko, Sato Natsuo, Yukimatu Akira Sessai
• Format: Report
• Language: English
• Published: 2005
• Subjects: Upper Atmosphere; Radio Observation; Global Climate Change; Antarc*; Antarctica; Iceland
• Online Access: https://uec.repo.nii.ac.jp/?action=repository_uri&item_id=8389; http://id.nii.ac.jp/1438/00008378/

Polar Mesosphere Summer Echoes (PMSE), which are regularly observed in summer months at polar latitudes, are strong radar backscatter from the upper mesosphere. They have been studied with ground-based radars whose frequency ranges from VHF to UHF. Recently, peculiar echos, which are interpreted as PMSE, were found to appear in the near range observations of Super Dual Auroral Radar Network (SuperDARN). This suggests a possibility that SuperDARN becomes a powerful tool for studying PMSE as a global scale phenomenon. In this paper, we statistically analysed occurrence frequency of the near backscatter echoes using two years measurements of the SuperDARN radars in Antarctica and Iceland. Occurrence percentage of the near range backscatter is enhanced significantly in summer months. Maximum is located at the summer solstice, where occurrence percentage reaches 80-90 % in Iceland and 70-80 % in Antarctica. Local time distribution of the echo occurrence has its maximum around local noon and minimum at 20LT. These characteristics of the near range echoes are quite similar to those of PMSE at VHF frequencies, which implies that near range observation of SuperDARN contains huge amount of PMSE. Interhemispheric difference of the echo occurrence probabilities are also estimated. Occurrence percentage averaged over summer months is 1.5 times larger in the Northern Hemisphere than that in the Southern Hemisphere, suggesting that occurrence of PMSE has actually an interhemispheric asymmetry. However, degree of interhemispheric asymmetry is much smaller than that predicted from the earlier VHF radar observation.