Investigating Gravity Waves in Polar Mesospheric Clouds Using Tomographic Reconstructions of AIM Satellite Imagery

Abstract

This research presents the first application of tomographic techniques for investigating gravity wave structures in polar mesospheric clouds (PMCs) imaged by the Cloud Imaging and Particle Size instrument on the NASA AIM satellite. Albedo data comprising consecutive PMC scenes were used to tomographically reconstruct a 3‐D layer using the Partially Constrained Algebraic Reconstruction Technique algorithm and a previously developed “fanning” technique. For this pilot study, a large region (760 × 148 km) of the PMC layer (altitude ~83 km) was sampled with a ~2 km horizontal resolution, and an intensity weighted centroid technique was developed to create novel 2‐D surface maps, characterizing the individual gravity waves as well as their altitude variability. Spectral analysis of seven selected wave events observed during the Northern Hemisphere 2007 PMC season exhibited dominant horizontal wavelengths of ~60–90 km, consistent with previous studies. These tomographic analyses have enabled a broad range of new investigations. For example, a clear spatial anticorrelation was observed between the PMC albedo and wave‐induced altitude changes, with higher‐albedo structures aligning well with wave troughs, while low‐intensity regions aligned with wave crests. This result appears to be consistent with current theories of PMC development in the mesopause region. This new tomographic imaging technique also provides valuable wave amplitude information enabling further mesospheric gravity wave investigations, including quantitative analysis of their hemispheric and interannual characteristics and variations.

Limited angle tomography of mesoscale gravity waves by the infrared limb-sounder GLORIA

“…However, the concept of 3-D tomography with sidewardslooking airborne instruments or sub-limb instruments (Song et al, 2017;Hart et al, 2018) is quite different and, thus, may exhibit different characteristics. In 2-D tomography a volume is reconstructed from rearwardlooking measurements on a moving platform that slice the volume into multiple 2-D images.…”

“…This model was developed to efficiently handle imager instruments and tomographic retrievals. It is based on JURAS-SIC (Hoffmann, 2006), which was previously used as a forward model for the evaluation of several satellite-and airborne remote-sensing experiments (e.g. Eckermann et al, 2006;Hoffmann et al, 2008;Weigel et al, 2010;Kalicinsky et al, 2013;Ungermann et al, 2016).…”

The MATS satellite mission – gravity wave studies by Mesospheric Airglow/Aerosol Tomography and Spectroscopy

“…In the stratosphere, techniques have been developed to overcome these limitations. The AIRS instrument on board the AQUA satellite measures upwelling radiation in a large number of spectral channels, and gravity waves have been retrieved from the upper troposphere to the mid-stratosphere (Hoffmann and Alexander, 2009;Gong et al, 2012). Additional techniques have been developed to maximize horizontal wave information from AIRS, utilizing either across-track nadir scans (Wright et al, 2017) or data from multiple satellite tracks .…”

Answers to the Referee Comment of Dr. Vern Hart on "Limited angle tomography of mesoscale gravity waves by the infrared limb-sounder GLORIA"

“…This model was developed to efficiently handle imager instruments and tomographic retrievals. It is based on JURAS-SIC (Hoffmann, 2006), which was previously used as a forward model for the evaluation of several satellite-and airborne remote-sensing experiments (e.g. Eckermann et al, 2006;Hoffmann et al, 2008;Weigel et al, 2010;Kalicinsky et al, 2013;Ungermann et al, 2016).…”

“…Former studies demonstrated the feasibility of 2-D tomography of rearward-looking satellite instruments for the retrieval of 3-D atmospheric structures such as GWs (Degenstein et al, 2004;Ungermann et al, 2010a;Hultgren et al, 2013). However, the concept of 3-D tomography with sidewardslooking airborne instruments or sub-limb instruments (Song et al, 2017;Hart et al, 2018) is quite different and, thus, may exhibit different characteristics. In 2-D tomography a volume is reconstructed from rearwardlooking measurements on a moving platform that slice the volume into multiple 2-D images.…”