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Abstract
Abstract. This study investigates the use of a vespagram-based approach as a tool for multi-directional comparison between simulated microbarom soundscapes and infrasound data recorded at ground-based array stations. Data recorded at the IS37 station in northern Norway during 2014–2019 have been processed to generate vespagrams (velocity spectral analysis) for five frequency bands between 0.1 and 0.6 Hz. The back azimuth resolution between the vespagram and the microbarom model is harmonized by smoothing the modeled soundscapes along the back azimuth axis with a kernel corresponding to the frequency-dependent array resolution. An estimate of similarity between the output of the microbarom radiation and propagation model and infrasound observations is then generated based on the image-processing approach of the mean square difference. The analysis reveals that vespagrams can monitor seasonal variations in the microbarom azimuthal distribution, amplitude, and frequency, as well as changes during sudden stratospheric warming events. The vespagram-based approach is computationally inexpensive, can uncover microbarom source variability, and has the potential for near-real-time stratospheric diagnostics and atmospheric model assessment.
Highlights
Microbaroms are infrasound waves with frequencies typically between 0.1 and 0.6 Hz generated by nonlinear interaction between counter-propagating ocean waves
In addition to prospective numerical weather prediction improvements, the suggested vespagram-based approach may be applied in multi-technology studies of atmospheric dynamics, for example initiatives building on the Atmospheric dynamics Research InfraStructure in Europe (ARISE) projects (Blanc et al, 2018, 2019)
3.2 Examination of major sudden stratospheric warmings. This is not the main objective of the current study, we examine the ability of the vespagrams to detect extreme atmospheric events, such as SSWs, and compare the model and the vespa processing for six selected events
Summary
Microbaroms are infrasound waves with frequencies typically between 0.1 and 0.6 Hz generated by nonlinear interaction between counter-propagating ocean waves. For a given frequency band, such vespagrams can be compared in a straightforward manner to microbarom soundscapes modeled for a station location, after applying a smoothing kernel which harmonizes the resolution given by the array response function main lobe and the microbarom model output Both the vespagram and the microbarom model provide power estimates as a function of time and back azimuth. In addition to prospective numerical weather prediction improvements, the suggested vespagram-based approach may be applied in multi-technology studies of atmospheric dynamics, for example initiatives building on the Atmospheric dynamics Research InfraStructure in Europe (ARISE) projects (Blanc et al, 2018, 2019) These aim at harvesting from synergies between ground-based infrasound observations, radar, and lidar systems, as well as airglow and satellite observations to monitor the middle atmosphere (Chunchuzov et al, 2015; Le Pichon et al, 2015; Hupe et al, 2019; Smets et al, 2019; Hibbins et al, 2019; Assink et al, 2019; Le Pichon et al, 2019).
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