Momentum and energy fluxes of monochromatic gravity waves observed by an OH imager at Starfire Optical Range, New Mexico

Abstract

The intrinsic characteristics of acoustic gravity waves can be deduced when the wave parameters are measured simultaneously with the winds and temperatures so that Doppler effects can be compensated. During February and April, 1995, five nights of OH imager observations of structure were made at the Starfire Optical Range near Albuquerque, New Mexico, simultaneously with Na wind/temperature lidar. The observed (CO) and intrinsic (CI) phase speeds were deduced for 161 gravity waves from the movement of horizontal structure observed in the images (taken every 2 min) and lidar horizontal wind profiles. The mean of the horizontal wavelengths and horizontal phase speeds for the five nights are λh ∼ 28.8 km, CO = 33.4 m s−1, and CI = 61.4 m s−1. The mean vertical wavelength, intrinsic period, and vertical phase speed are λz ∼ 26.6 km, τI ∼ 7.7 min, and Cz ∼ 61.5 m s−1, respectively. Because of their large vertical phase velocities, these waves can propagate to almost 200‐km altitude before they are damped by molecular diffusion. The mean vertical flux of horizontal momentum (Fm) was 21.9 m2 s−2, and the mean zonal and meridional components were −5.3 and +6.1 m2 s−2, respectively. Monochromatic waves with τI > 1 hour and λz < 20 km were also characterized using the Na lidar wind and temperature profiles [Yang, 1998]. The waves measured simultaneously by the lidar in the same volume of atmosphere observed by the imager had a mean momentum flux of Fm = 13.3 m2 s−2. The mean zonal and meridional momentum fluxes of the combined data sets are −3.2 and +3.6 m2 s−2, respectively.