The Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX)

The Mesosphere-Lower Thermosphere Turbulence Experiment (MTeX), is designed is to contribute to answering one of the key questions in solar-terrestrial science: How do meteorological processes control the impact of solar processes on the Earth's atmosphere? The goal of MTeX is to answer the specific question: What is the contribution of wave-generated turbulence to energetics and mixing in the mesosphere and lower thermosphere (MLT) in the presence of persistent regions of stability and instability? During recent Arctic winters, satellite observations have revealed significant transport of nitrogen oxides (produced by energetic particle precipitation) downward from the thermosphere into the mesosphere, stratosphere and ozone layer. These events have been associated with sudden stratospheric warming events (SSWs) where strong downward transport is observed in the recovery phase of the SSW. However, simulations with current coupled chemistry circulation models indicate that the observed transport cannot be explained by mean flow advection alone. Simulation of the observed transport of nitrogen oxides requires diffusive transport from the thermosphere where the magnitude of the diffusive transport is on order of the mean flow transport. Turbulence is both characterized and measured in terms of energy dissipation rates (used in circulation studies) and eddy diffusion coefficients (used in chemical transport studies). Variability over several orders of magnitude has been reported in turbulence measurements due to both the variety of background conditions present and methods used. High-resolution fluid dynamic simulations continue to raise questions about the physical and statistical assumptions used in determining turbulent characteristics. We propose to make repeated measurements of turbulence in the presence of a Mesospheric Inversion Layer (MIL) in January-February 2015 at Poker Flat Research Range, Chatanika, Alaska. The MIL (~70-90 km) and gravity wave activity in the stratosphere mesosphere and lower thermosphere (~40-90 km) will be monitored by a ground-based Rayleigh lidar. MILs are characterized by a inversion layer with increased stability overlaid by an unstable region with near adiabatic lapse rate. Once the MIL forms, a rocket-borne payload with a neutral sensor (CONE instrument) and plasma sensor suite (Langmuir and impedance probes) will be launched. MILs persist for periods of several hours, and a second payload will be launched about an hour after the first about one gravity-wave period later. The investigation is designed to provide high-resolution (m resolution) in-situ measurements of turbulence fluctuations in the altitude regions of enhanced stability and instability, and ground-based measurements of the stability and instability environment and wave activity (km and 10's of min). The observations will be used to create simulation scenarios that will quantify the eddy dissipation rates and diffusivity associated with the wave-generated turbulence.