Mesopheric Winds from Lidar Observations of Atmospheric Sodium

摘要

Laser radar observations of the atmospheric sodium layer made by various groups of workers during the past decade show that the layer exhibits considerable time varying structure. Horizontally spaced measurements of this structure, and use of the results of these observations to derive horizontal velocities in the height range 82 to 99 km are described. The measurements were made with a steerable lidar operating at a fixed zenith angle of 20.9 deg and pointed at each of three azimuths in turn, the complete sequence taking five minutes. The azimuths were chosen such that the intersections of the lidar beam with the sodium layer formed a triangle with approximately 60 km sides. The velocities calculated from the derived time shifts were found to vary with height in an oscillatory manner, with amplitude increasing with height. The E-W component showed a vertical wavelength of approximately 10 km, the N-S component a wavelength of 5 km, and the magnitude of the velocity varied between 6 and 146 m/sec.