Radar observations and dynamics of the polar summer mesosphere
Abstract
The lowest temperatures and the highest clouds on Earth, complex ion chemistry, large amplitude waves, and intense radar scatter make the summer polar mesosphere a fascinating atmospheric region. Two aspects of the region related to radar echoing and detection are addressed: the role of the Stokes drift in measurements of the seasonal circulation, and the extension of the electron density variance spectrum to length scales smaller than those of the driving turbulence. Although the mass flux rate at the summer polar mesopause must be about 1 cm/s upward to be consistent with the temperature, radars measure 20 to 30 cm/s downward. This surprising result was verified with four years of radar data. After discussing the Stokes drift in detail, the calculation is generalized to include a wave spectrum. The results indicate that the Stokes drift is not large enough to explain the radar measurements. As an alternative, it is suggested that the radar is detecting the fall speed of charge aerosols. Structuring of the polar summer mesospheric electron density at scales shorter than the inner scale of turbulence is necessary to explain the intensity of VHF radar echoes.
- Publication:
-
Ph.D. Thesis
- Pub Date:
- 1991
- Bibcode:
- 1991PhDT........24H
- Keywords:
-
- Atmospheric Chemistry;
- Atmospheric Stratification;
- Electron Density (Concentration);
- Ionic Reactions;
- Mesosphere;
- Radar Scattering;
- Summer;
- Aerosols;
- Mesopause;
- Polar Regions;
- Radar Data;
- Radar Detection;
- Radar Echoes;
- Spectra;
- Turbulence;
- Very High Frequencies;
- Geophysics