Observations of mesospheric wind velocities: 1. Gravity wave horizontal scales and phase velocities determined from spaced wind observations

Horizontal scales and phase velocities of upper middle atmosphere (60–110 km) gravity waves determined from preliminary analysis of spaced wind observations obtained with a dual bistatic radar (Gravnet), based on and operated together with the Saskatoon MF radar are presented. In the observed period range of 10–100 min, horizontal scales increase from values of ∼44 km at 10 min to ∼211 km at 100 min, while observed phase speeds decrease from values of ∼72 m/s at 10 min to ∼34 m/s at 100 min. Typical rms perturbation velocities are ∼5 m/s. Calculation of intrinsic wave parameters indicates that in the intrinsic period range of 10–100 min, horizontal scales increase from values of ∼68 km at 10 min to ∼119 km at 100 min, with intrinsic phase speeds of ∼93 m/s at 10 min and ∼20 m/s at 100 min. The corresponding values of vertical wavelength are 30 km and 6 km, respectively.