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This paper introduces a method of observing upper atmosphere (tropopause to over 200 Km, day and night) dynamics with simple small static passive broadband gas filtered imagers in low earth orbit. The method produces modulated signals by Doppler Scanning with Gas Filters (DSGF) and observing the atmosphere over a range of angles, from limb to nadir. These modulated signals, suggested by Curtis in 1974, but now readily exploited with modern infrared detector arrays, are found to have extraordinary unique information content, enabling the observation of wind and temperature at unprecedented spatial scales. These observations can now be achieved with simple static infrared imagers, and without absolute calibration of the sensed radiance. CUAD is the upper atmosphere component of a proposed meteorological suite of small sensors called METNET.

Although mountain waves (MWs) are thought to be a ubiquitous feature of the wintertime southern Andes stratosphere, it was not known whether these waves propagated up to the mesopause region until Smith et al. (2009) confirmed their presence via airglow observations. The new Andes Lidar Observatory at Cerro Pachon in Chile provided the opportunity for a further study of these waves. Since MWs have near-zero phase speed, and zero wind lines often occur in the winter upper mesosphere (80 to 100 km altitude) region due to the reversal of the zonal mean and tidal wind, MW breakdown may routinely occur at these altitudes. Here we report on very high spatial/temporal resolution observations of the initiation of MW breakdown in the mesopause region. Because the waves are nearly stationary, the breakdown process was observed over several hours; a much longer interval than has previously been observed for any gravity wave breakdown. During the breakdown process observations were made of initial horseshoe-shaped vortices, leading to successive vortex rings, as is also commonly seen in Direct Numerical Simulations (DNS) of idealized and multiscale gravity wave breaking. Kelvin-Helmholtz instability (KHI) structures were also observed to form. Comparing the structure of observed KHI with the results of existing DNS allowed an estimate of the turbulent kinematic viscosity. This viscosity was found to be around 25 m2/s, a value larger than the nominal viscosity that is used in models.

Individual small weather satellites have been previously presented including GPS-Radio Occultation, Infrared Sounding, Microwave Radiometry, Multispectral Imaging, and Gas-Filter Correlation Radiometry, but to our knowledge not as a comprehensive on-orbit system. In this paper, for the first time, we describe a new global Meteorological Network - MetNetTM using multiple electro-optical and microwave satellite constellations. We shall provide a brief overview of several candidate small weather satellites including Doppler Wind Temperature Sounder (DWTSTM), Moderate Resolution Imaging Spectro-Radiometer in 3U (MODIS-3U), the Compact Microwave Sounder (CMS), the Compact Infrared Sounder CIS), the stellar occultation temperature retrieval CubeSat (T-STAR), the Aerosols and Cloud Characterization Imaging Polarimeter (ACCIP), and the High-Altitude Temperature Sounder (HATSTM). These instrument constellations when combined shall cover the full range of altitudes from surface to thermosphere, at significantly higher spatial resolutions than available from GEO satellites, with improved retrievals through synergistic data techniques. The disaggregation of instruments onto several spacecraft simplifies the production flow, as well as allowing more flexibility in calibration maneuvers such as lunar scans and cross-calibrations. The full range of measurements shall include horizontal wind speeds, 3D temperature soundings, humidity, precipitation, sea surface temperature, cloud characterization, aerosol size distributions, and atmospheric chemistry.

The Doppler Wind and Temperature Sounder (DWTS) is novel sensor concept for measuring global winds and temperatures from cloud-top to the thermosphere. This will significantly improve medium- and long-range weather forecasts and enable more advanced tracking of severe storms. The approach uses the inherent high spectral resolution from gas filter correlation radiometry to simultaneously measure the Doppler shift and linewidth of limb emission spectra as viewed from low-Earth orbit. DWTS images the limb through low-pressure gas cells containing CO2, NO and NO2. We describe here how very accurate vector winds and kinetic temperatures can be inferred from these observations. Profiles of temperature and wind can be measured day and night continuously from 15 to over 250 km at intervals of 10 km along-track with less than 2% uncertainty. A constellation of 6-12 DWTS instruments on small satellites would provide unprecedented observations of global atmospheric dynamics from the lower stratosphere into the middle thermosphere, greatly improving weather and storm forecasting. We present the current status and plans to realize this important mission. &nbsp

第2回極域科学; 会場・会期: 2011年11月14日（月）-18日（金）: 国立極地研究所2階大会議室および国立国語研究所２階講堂