Observing Atmospheric Gravity Waves from the Space Station
Small-scale atmospheric gravity waves (GWs), which are formed due to topography (i.e. mountains), convection, or strong wind jets, transport energy and momentum across long distances with wavelengths from tens to hundreds of km. GWs propagate until they reach instability, break, and generate turbulence on the scale of 10 km to diffusion length scales (below 1 m). GWs drive high altitude weather phenomena with deviations in atmospheric density and turbulence that accelerate stratospheric winds, producing the mean circulation, Quasi Biennial Oscillation (QBO), and breakdown of the polar vortex. Therefore, to develop a comprehensive understanding of the behavior of the upper atmosphere, it is vital to observe and understand these upper atmospheric gravity waves. However, gravity waves, and the turbulence they produce, are difficult to observe from the ground and are currently not well characterized.
Four different instruments able to observe GWs are scheduled to launch in mid-2023 to join the suite of instruments on the International Space Station (ISS). The Atmospheric Waves Experiment (AWE) measures the airglow temperature at a 20 km by 7 km horizontal resolution. The Experiment for Characterizing Lower Ionosphere & Production of Sporadic-E (ECLIPSE) measures both horizontal and vertical profiles of electron and ion density between 60 km to 400 km altitude. The Variable Voltage Ion Protection Experiment (VVIPRE) measures the vertical profile of electron and ion density at a 30 km resolution. The Stellar Occultation Hypertemporal Imaging Payload (SOHIP) measures atmospheric refraction soundings from 10 km to 60 km altitudes at 10 m vertical resolution via stellar occultation. With a high vertical resolution, SOHIP measures turbulence via stellar scintillation in addition to vertical GW via stellar refraction.
In this work, we investigate whether measurements from these four different satellite-based instruments can be combined to observe GWs propagating from the troposphere to ionosphere. We will show a case study with simulated measurements of convective GWs from each of the instruments. The lower atmospheric simulation models a strong convective system forming GWs with the Weather Research & Forecasting (WRF) model from the surface to 60 km altitude. The upper atmospheric simulation models the medium-scale traveling ionospheric disturbances with the SAMI3 numerical model (Sami3 is Also a Model of the Ionosphere) based on lower atmospheric boundary conditions from a strong convective storm.
The simulated data is sampled based on the instrument viewing geometries from the ISS, and the spatial and temporal resolution are based on the instrument operating parameters and the ISS orbit. Additionally, the instruments measure different properties of the atmosphere. While SOHIP and AWE observe temperature, ECLIPSE and VVIPRE observe ion density. Therefore, each instrument has a different sensitivity to GWs, which must be considered when performing data fusion and assimilation into models.
We will discuss the feasibility of observing upper atmosphere disturbances with these new satellite observations. The diverse spatial resolution, quantities measured, and viewing geometries among the four instruments can provide a more complete understanding of GWs than one measurement alone.
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This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. LLNL-ABS-849302