Large-scale gravity wave perturbations in the mesopause region above Northern Hemisphere midlatitudes during autumnal equinox: a joint study by the USU Na lidar and Whole Atmosphere Community Climate Model

Abstract. To investigate gravity wave (GW) perturbations in the midlatitude mesopause region during boreal equinox, 433 h of continuous Na lidar full diurnal cycle temperature measurements in September between 2011 and 2015 are utilized to derive the monthly profiles of GW-induced temperature variance, T ′ 2 , and the potential energy density (PED). Operating at Utah State University (42° N, 112° W), these lidar measurements reveal severe GW dissipation near 90 km, where both parameters drop to their minima (∼ 20 K 2 and ∼ 50 m 2 s −2 , respectively). The study also shows that GWs with periods of 3–5 h dominate the midlatitude mesopause region during the summer–winter transition. To derive the precise temperature perturbations a new tide removal algorithm suitable for all ground-based observations is developed to de-trend the lidar temperature measurements and to isolate GW-induced perturbations. It removes the tidal perturbations completely and provides the most accurate GW perturbations for the ground-based observations. This algorithm is validated by comparing the true GW perturbations in the latest mesoscale-resolving Whole Atmosphere Community Climate Model (WACCM) with those derived from the WACCM local outputs by applying this newly developed tidal removal algorithm.