Remote sensing of discrete stratospheric gravity-wave structure at 4.3-μm from the MSX satellite

Distinctive structure in the 4.3-mu m spectral region has been imaged by the SPIRIT 3 radiometer on the MSX satellite observing the cloud-free atmosphere. We show nadir, high-nadir-angle (NA) sublimb, and limb images which, coupled with radiative transfer analysis, indicate that this structure originates from internal gravity waves (GWs). Such structure occurs in a significant fraction of both below-the-horizon (BTH), or sublimb, and above-the-horizon (ATH), or limb, observations in both MSX 4.3-mu m channels. The structure has different morphology from clouds and has spatial scales appropriate for atmospheric GWs. Calculation of contribution functions (CFs), or weighting functions, for MSX filters and viewing conditions confirms that the BTH GW structure originates from altitudes near 40 km. We believe this is the first high-resolution imaging of atmospheric GWs from space in the mid-wave infrared (MWIR) spectral region. In addition, the technique provides structure imaging capabilities at upper stratospheric altitudes inaccessible to airglow imagery.