Horizontal wave number spectra of density and temperature perturbations in the mesosphere measured during the 4 August flight of ANLC‐93

Abstract

On 4 August 1993 during ANLC‐93 the NCAR Electra completed a round‐trip flight west from Edmonton, Alberta to the Pacific Ocean. The University of Illinois Na lidar and Utah State Michelson interferometer observations were used to study the vertical wave number (m) and zonal wave number (k) spectra of relative atmospheric density, Na abundance, OH emission intensity, and rotational temperature perturbations. The spectral indices of the m‐ and k‐spectra inferred from the lidar data are smaller than those reported by Hosteller and Gardner [1994] over the mid‐Pacific but similar to those reported by Kwon et al. [1990] over the Rocky Mountains and Great Plains. These differences may be a consequence of different gravity wave source characteristics over the Rocky Mountains compared to the equatorial mid‐Pacific region where convection is strong and orographic forcing is absent. The Na abundance spectrum closely follows a power‐law over the range from k = 2π/(1000 km) to 2π/(3 km). This observation contradicts simple gravity wave theory which predicts that the abundance spectrum should fall rapidly to zero at wave numbers larger than ∼2π/(25 km).