Gravity wave observation and ray tracing in the Arctic upper atmosphere
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University of New Brunswick
Gravity waves (GWs) are ubiquitous throughout Earth’s atmosphere. Yet, their inadequate representation in global models is a source of uncertainty in accurately evolving the state of the atmosphere. It is therefore imperative to improve our understanding of their spectra and origins. In this study, GWs are observed in the mesosphere and lower thermosphere (MLT) via their perturbations to airglow layers above Eureka, Canada (80◦N, 86◦W). GW observations from all-sky imaging and high-precision wind measurements with the E-Region Wind Interferometer (ERWIN) are conducted at the Polar Environmental and Atmospheric Research Laboratory (PEARL) to allow extraction of wave parameters. Ray tracing is performed on observed waves to diagnose potential sources using the Gravity Wave Regional or Global Ray Tracer (GROGRAT), developed by Marks and Eckermann. Background atmosphere datasets are retrieved from the extended Canadian Middle Atmosphere Model (CMAM) for tracing the waves. Topography is identified as a likely leading mechanism for small-scale secondary wave (horizontal wavelength < 100 km) generation above Ellesmere Island during the 2008-2009 wintertimes. A case study of a large-scale GW on Nov. 20, 2008 revealed probable origins linked to a strong low pressure system and jet stream over Eastern Canada. The paper concludes with an analysis exploring the sensitivity of GROGRAT-derived ray trajectories to launch parameters and contrasting backgrounds.