부산대학교 도서관

Satellite-based tomography provides a new approach to studying Polar Mesospheric Clouds (PMCs). In this paper, we explore the tomographic dataset from the Odin satellite to study structures and microphysics of PMCs. The dataset is based on special limb scans over limited altitude ranges during 256 orbits in the years 2010-2014. The focus of the analysis is on latitudinal and hemispheric variation. The basic results are in line with earlier studies by lidars and conventional satellite limb measurements. We find a decrease with decreasing latitude of PMC occurrence frequency, brightness, ice water content and particle size. As for hemispheric differences, we find that occurrence frequency, brightness, ice water content and particle size are generally less in the Southern Hemisphere than in the Northern Hemisphere. Our limited Southern Hemisphere dataset does not show the general finding of lidar studies that PMCs in the South occur at higher altitudes than in the North. All data products show substantial diurnal variations, likely connected to tidal activity. As a basic microphysical parameter, the altitude gradient of the PMC particle size does not show any significant latitudinal or hemispheric dependence. This suggests a PMC growth/sedimentation process that is largely the same everywhere. The data presented here demonstrate the value of satellite-based tomography as a complement to lidars and conventional satellite measurements by providing global coverage in combination with both vertical and horizontal resolution.