资源环境科技发展态势分析平台

There is currently an ambiguity in what controls polar mesospheric cloud (PMC) periodicities near 83km altitude. This is primarily because satellite and ground-based data sets cannot resolve global mesospheric temperature variability over the diurnal cycle. To address this limitation, we employ a global meteorological analysis and forecast system that assimilates mesospheric satellite data with two significant advances. The first is that we use output at a more rapid one hourly cadence, allowing for a quantitative description of diurnal (24h), semidiurnal (12h), and terdiurnal oscillations. The second is that the output drives a simple PMC parameterization which depends only on the local temperature, pressure, and water vapor concentrations. Our study focuses on results from July 2009 in the Northern Hemisphere and January 2008 in the Southern Hemisphere. We find that the 24h migrating temperature tide as well as the 12h and 24h nonmigrating tides dominate northern PMC oscillations whereas the 12h and 24h nonmigrating tides dominate southern oscillations. Monthly averaged amplitudes for each of these components are generally 2-6K with the larger amplitudes at lower PMC latitudes (50 degrees). The 2day and 5day planetary waves also contribute in both hemispheres, with monthly averaged amplitudes from 1 to 3K although these amplitudes can be as high as 4-6K on some days. Over length scales of similar to 1000km and timescales of similar to 1week, we find that local temperature oscillations adequately describe midlatitude PMC observations.