Comparison of tomographic neutral density retrieval with climatological and general circulation models

Abstract:

A new technique for deriving neutral density from the inversion of ultraviolet dayglow measurements has been developed to interpret measurements made by Special Sensor Ultraviolet Limb Imager (SSULI). The tomographic inversion methodology and initial results are presented in a companion presentation (see Dymond et al. [2020]). A comparison of some initial results with both a climatological and a general circulation model is presented here. First, the reconstructed neutral density profiles are compared to climatological predictions from the recently updated NRLMSIS 2.0 model. Second, SSULI-derived density profiles are compared to the National Center for Atmospheric Research (NCAR) thermosphere-ionosphere-mesosphere-electrodynamics general circulation model (TIME-GCM) nudged with reanalysis data from the Navy Global Environmental Model, high-altitude (NAVGEM-HA). Day-to-day variability is not meant to be captured by climatological models like NRLMSIS, so reasonably large discrepancies are expected. Comparisons with a physics-based model like TIME-GCM constrained by a large dataset like NAVGEM-HA are expected to compare more closely with the reconstructed densities, however the similarities and differences between all three will be discussed.