Satellite observations of atmospheric variances: A possible indication of gravity waves

The Microwave Limb Sounder (MLS) on the Upper Atmosphere Research Satellite has now produced the first global maps of small-scale variances in the middle atmosphere. Initial analyses are presented here that suggest these variances are due to gravity waves, and the technique used to extract gravity wave information from saturated radiance measurements is described. Observations at 30–80km altitudes show that the variances of horizontal scales less than ∼100km are strongly correlated with upper tropospheric convection, surface topography and stratospheric jetstreams. MLS monthly averages during solstice periods suggest that the normalized variance amplitude grows exponentially with height in the stratosphere, and saturates in the mesosphere as expected from wave breaking and dissipation at these altitudes.

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