The earth's turbopause and mesopause are both at around 100 KM altitude and mark a transition from gravity wave (GW) propagation and small-scale turbulence in the weakly stratified upper mesosphere to…

This federal contract award, valued at $1,315,462, was granted to Clemson University's Division of Research by the National Aeronautics and Space Administration (NASA) Shared Services Center. The contract is for a research grant to better understand the dynamics of the upper mesosphere and lower thermosphere regions, particularly focused on the transition from gravity wave propagation to turbulence near the turbopause around 100 km altitude. The project aims to use sounding rocket experiments, ground-based observations, and numerical modeling to investigate the vertical vorticity, divergence, and turbulent structures associated with nonlinear gravity wave interactions in this critical atmospheric region. This research aligns with NASA's Heliophysics Science Goal 1 to explore physical processes in the space environment. The contract does not utilize a set-aside designation and has an ultimate completion date of April 1, 2026.

The earth's turbopause and mesopause are both at around 100 KM altitude and mark a transition from gravity wave (GW) propagation and small-scale turbulence in the weakly stratified upper mesosphere to the strong winds and extreme wind shears in the highly stratified lower thermosphere. Observations of kinetic energy wavenumber spectra and latest GW-resolving gcms show evidence for a universal spectral regime at mesoscales (10-500 KM), often with a transition in the spectral power law around 200 KM. Gcms should be able reproduce this spectral regime and the associated downward energy cascade, including physically consistent diffusion schemes, for modeling momentum, heat and constituent transport across the mesopause into the thermosphere and ionosphere, which is critical for understanding space weather. However, there is a severe lack of detailed observations of mesoscale dynamics near the turbopause. Our science goal is to better understand nonlinear GW interactions in the upper mesosphere and lower thermosphere and the formation of vortices and stratified turbulence. Science question 1: can we identify vertical vorticity at mesoscales (10-200 KM) associated with the nonlinear interaction and dissipation of GWS, particularly, within a stratified background? What are the quantitative proportions of horizontal divergence and vertical vorticity in this process? Science question 2: what are the structures at sub-mesoscales (1-10 KM) associated with nonlinear GW interaction? What is the spatial distribution of isotropic and stratified turbulence at these scales? These questions will help to address the NASA heliophysics science goal 1 "explore the physical processes in the space environment from the sun to the earth and throughout the solar system", and more specifically, the heliophysics roadmap objective "understand the role of turbulence and waves in the transport of mass, momentum, and energy (F5)" as part to "solve the fundamental mysteries of heliophysics (f)". Our methodology is based upon a sounding rocket experiment comprising two salvoes with each two rockets launched from andoya space center, norway in winter. One rocket in each salvo will deploy 16 TMA ampules for horizontally and vertically distributed wind and vorticity measurements and also carry ionization gauges to measure neutral temperatures and density fluctuations. The other rocket will deploy TMA trails for wind measurements and observing the evolution of turbulent structure the primary science region is between 80 and 120 KM. The ampule subpayloads are based on technology developed for the azure and c-REX missions, but IT is the first time that they would be employed in an experiment focused on turbopause neutral dynamics. The launches will be supported by state-of-the-art ground-based techniques. We propose to use the amtm to image temperatures, GWS and small-scale activity in the OH layer near 87 KM. Strong GW activity in the common volume with the rocket measurements would trigger the launch sequence for each salvo. The mmaria meteor radars in northern norway will provide detailed wind maps between 80 and 100 KM that allow the observation of divergence and vorticity at mesoscales. Alomar rayleigh doppler lidar will provide wind and temperature profiles up to 80 KM and monitor background GW and tidal activity. We propose to achieve closure by combining observational data with numerical modeling of nonlinear gravity wave dynamics from the mesopause to thearound the mesopause and turbopause. Time-dependent background profiles of wind and temperature will provide basis for simulating gravity wave propagation, instability, secondary wave and turbulence generation, and resulting vorticity and divergence fields from sub-kilometer to 100-KM scales. Numerical results will include simulations of airglow and tracer species density perturbations, to enable comparisons with observed small-scale structures and elucidate dynamics.