Mapping atmospheric gravity wave activity with limb-viewing microwave radiometer (UARS MLS)

The Upper Atmosphere Research Satellite Microwave Limb Sounder (UARS MLS) has three double-sideband radiometers measuring atmospheric O ₂, O₃, ClO, and H₂O features near 63, 183 and 205 GHz. The 63-GHz radiometer has 15 spectral channels with channel 8 centered at the center of O₂ lines and channels 1/15 at ±200MHz from the center. In the normal operation MLS stepscans atmospheric limb from 90km to the surface in 65 seconds with -2 second integration time on each measurement. The limb radiances become saturated as the antenna views tangent heights near the surface. Showing little dependence on pointing, the saturated radiance basically measures atmospheric temperature of the saturation layer. Radiance fluctuations, therefore, can be reported as temperature fluctuations at that layer plus instrument noise. This paper describes various variance analysis techniques that have been applied to MLS radiances and provides some interpretation of observed features in terms of temperature weighting function, sampling pattern and wave propagation