Polar mesospheric clouds observation from the Himawari geostationary meteorological satellite

Polar mesospheric clouds (PMCs) consist of water-ice particles, and have been observed near the summer polar mesopause region. Production and disruption of PMC are sensitive to the background mesospheric state, such as the temperature and water vapor conditions. Its distribution is strongly affected by the background wind. Hence, PMC is a good proxy for the thermal structure and dynamics in the high latitude summer mesosphere. Observations of PMC have been widely performed by various methods from the ground as well as from Low-Earth-Orbit (Leo) satellites. However, these methods have some limitations, especially in local time coverage or observational continuity to monitor the long-term PMC activity.

In the presentation, we report PMC observations by the Advanced Himawari Imager (AHI) onboard Himawari-8, the Japanese Geostationary-Earth-Orbit meteorological satellite. In the regular operation of AHI, a full-disk image of the Earth is obtained every 10 minutes with a spatial resolution of ~ 1 km. In the blue visible band of AHI (Band No: 1, Central wavelength: 470 nm), we found emissions which are supposed to originate from PMCs at the Earth's limb region of the full-disk images. The emission height is 82 - 85 km, that is the typical altitude of PMCs reported in previous studies. The seasonal variations of the emission (e.g. a peak slightly behind the summer solstice) are also consistent with those reported. By analyzing its spatial and temporal characteristics, we confirmed that the emission is surely due to the scattering of the sun light by PMCs. The data set of PMC from the GEO satellite has great advantages in local time coverage and observational continuity for the long-term monitoring. PMC observation by Himawari-8 is expected to provide new information on the PMC studies, majority of which are based on the ground-based or LEO satellite observations.