Turbulence measurements and implications for gravity wave dissipation during the MaCWAVE/MIDAS rocket program

Abstract

Three altitude profiles of turbulent energy dissipation rates measured during the MaCWAVE/MIDAS summer rocket program are presented. All measurements show near continuous turbulent layers from ∼72–90 km altitude. Above 82 km altitude measured dissipation rates are comparable to former results. Below 82 km the MaCWAVE/MIDAS measurements provide the first evidence for turbulence in summer at these altitudes ever obtained. This unusual turbulence activity is accompanied by a reduced altitude of the zonal wind maximum, colder temperatures below 85 km, and enhanced gravity wave amplitudes above ∼75 km. The larger gravity wave amplitudes can be explained by the different local thermal structure through the wave amplitude dependence on the buoyancy frequency. These larger wave amplitudes lead to wave breaking, turbulence production, and forcing of the zonal wind at lower altitudes. Our measurements hence imply that the altitude of the zonal wind maximum is a sensitive indicator for the altitude distribution of turbulence in the upper mesosphere.