ALBERT

Description: 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 (CIPS) instrument on the NASA AIM satellite. Albedo data comprising consecutive PMC scenes were used to tomographically reconstruct a 3D layer using the Partially Constrained Algebraic Reconstruction Technique (PCART) algorithm and a previously developed “fanning” technique [ Hart et al. , 2012]. For this pilot study, a large region (760 x 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 2D 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 [ Chandran et al. , 2009; Taylor et al. , 2011]. These tomographic analyses have enabled a broad range of new investigations. For example, a clear spatial anti-correlation 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 inter-annual characteristics and variations.