Thermospheric Nocturnal Wind Climatology Observed by Fabry–Perot Interferometers over the Asia–Oceania Region

Abstract

This study shows the horizontal structure of climatology of thermospheric nocturnal winds at a height of about 250 km in the Asia–Oceania region for the first time using observations made with Fabry–Perot interferometers (FPIs; optical wavelength of 630.0 nm). The locations of the FPIs used in this study were Shigaraki (Japan, 34.8ºN, 136.1ºE), Chiang Mai (Thailand, 18.8ºN, 98.9ºE), Kototabang (Indonesia, 0.2ºS, 100.3ºE), and Darwin (Australia, 12.4ºS, 131.0ºE). The observation data underwent quality control that involved consideration of cloud information, wind speed value, and the standard deviation of results obtained from synchronous fringe images; about 30 % of observation data from all the four stations were deemed suitable for use. The nocturnal diurnal changes at Shigaraki according to the local solar time was generally consistent with changes in China at similar latitudes, although the amplitudes were slightly different. The other three stations showed seasonal changes that were continuous with patterns for Shigaraki in each season, and the Chiang Mai and Darwin stations observed seasonal/diurnal changes similar to those observed by stations at similar latitudes on the American continent. Although there were fewer samples for Chiang Mai, Kototabang, and Darwin in the rainy season compared to that of Shigaraki, the seasonal climatology reported here can be used to provide a background long-term average status for describing anomalous events and extremes having different causes.