Simultaneous, common‐volume lidar observations and theoretical studies of correlations among Fe/Na layers and temperatures in the mesosphere and lower thermosphere at Boulder Table Mountain (40°N, 105°W), Colorado

Abstract

AbstractSimultaneous and common‐volume observations of Fe density, Na density, and temperatures in the mesosphere and lower thermosphere were made for 12 nights with an Fe Boltzmann lidar and a Na Doppler lidar at the Table Mountain Lidar Facility (40.13°N, 105.24°W) near Boulder, Colorado, in August and September 2010. We derive the correlations among temporal variations of Fe/Na densities and temperatures, eliminating the covariance bias via computing the cross correlations between Fe (Na) density and Na (Fe) temperature perturbations. The Fe‐Na density correlation is positive below the Fe layer peak and above the Na peak where the Fe/Na density gradients have the same signs but becomes negative in between the Fe and Na peaks where the gradients are opposite. The large correlation between temperature and density fluctuations is positive on the layer bottomside but negative on the topside with the transitions occurring near the layer peaks. The relative Fe/Na variances reach minimum near the layer peaks but rapidly increase and exceed the relative temperature variance significantly toward edges. These observations can be largely reproduced by theoretically modeling the metal layer responses to the wave‐induced perturbations only through dynamic processes with a Gaussian stationary density distribution. These results suggest that the dynamic effects (mainly the vertical displacement) induced by gravity waves or tides dominate the observed short‐term density and temperature variations over a night. We explain the Fe/Na gradient difference observed at the bottomside via the chemical “shelf” around 80 km for reactive chemicals and the Fe/Na layer height difference.