Mesospheric Inversion Layers at Chatanika, Alaska (65°N, 147°W): Rayleigh lidar observations and analysis

Abstract

AbstractRayleigh lidar observations at Poker Flat Research Range, Chatanika, Alaska (65°N, 147°W), have yielded density and temperature measurements from 40 km to 80 km. These measurements have been made under clear skies at night between November 1997 and May 2009. We have identified and characterized 79 Mesospheric Inversion Layers (MILs) in the 40–70 km altitude region on 56 of 117 nights of observations between August and May. These 79 MILs have an average amplitude of 13 K, peak altitude of 61 km, topside lapse rate of 6 K/km, depth or thickness of 3 km, base altitude of 58 km, bottomside gradient of 5 K/km, and downward vertical velocity of 0.1 km/h based on the 2 h temperature profiles. MILs occur with a nightly occurrence rate of 48%, more frequently than previously reported at Arctic sites, but less frequently than at lower latitude sites. MILs are embedded in the larger planetary wave structure. MILs are found to occur most commonly in January as has been reported from lower latitude sites. We find that the planetary wave‐1 amplitudes are a factor 1.3 larger at an altitude of 5.0–6.5 scale heights (~32–39 km) on days when MILs are observed than when they are not observed. The planetary wave‐2 amplitudes are not significantly different when MILs are present and absent. We find that Eliassen‐Palm flux divergences at an altitude of 7–8 scale height (~45–52 km) are a factor 2.0 larger on nights when MILs are observed than when they are not observed. We also find that gravity wave potential energy densities are a factor 1.3 larger on nights when MILs are observed than on nights when they are not observed.