The development of an inversion technique to extract vertical current profiles from X-band radar observations

TitleThe development of an inversion technique to extract vertical current profiles from X-band radar observations
Publication TypeJournal Article
Year of Publication2016
AuthorsCampana J., Terrill E.J, de Paolo T.
JournalJournal of Atmospheric and Oceanic Technology
Volume33
Pagination2015-2028
Date Published2016/09
Type of ArticleArticle
ISBN Number0739-0572
Accession NumberWOS:000384535300014
Keywordscurrent shear; high-frequency radar; image sequences; multifrequency hf radar; ocean; sea-surface; surface currents; upper; variability; waves
Abstract

The influence of wave-current interactions on time series of marine X-band radar backscatter maps at the mouth of the Columbia River (MCR) near Astoria, Oregon, is examined. The energetic wave environment at the MCR, coupled with the strong tidally forced currents, provides a unique test environment to explore the limitations in accurately determining the magnitude and vertical structure of upper-ocean currents from wavefield measurements. Direct observation in time and space of the wave-induced radar backscatter and supporting acoustic Doppler current profiler (ADCP) current measurements provide a rich dataset for investigating how currents shift the observed wave dispersion relationship. First, current extraction techniques that assume a specific current-depth profile are tested against ADCP measurements. These constrained solutions prove to have inaccuracies because the models do not properly account for vertical shear. A forward solution using measured current profiles to predict the wavenumber-Doppler shift relationship for the range of ocean waves sensed by the radar is introduced. This approach confirms the ocean wavefield is affected by underlying vertical current shear. Finally, a new inversion method is developed to extract current profiles from the wavenumber-dependent Doppler shift observations. The success of the inversion model is shown to be sensitive to the range of wavenumbers spanned by observed Doppler shifts, with skill exceeding 0.8 when wavenumbers span more than 0.1 radm 21. This agreement when observations successfully capture the broadband wavefield suggests the X-band backscatter is a viable means of remotely estimating current shear.

DOI10.1175/jtech-d-15-0145.1
Short TitleJ. Atmos. Ocean. Technol.
Student Publication: 
No