Removing Spurious Low-Frequency Variability in Drifter Velocities

TitleRemoving Spurious Low-Frequency Variability in Drifter Velocities
Publication TypeJournal Article
Year of Publication2013
AuthorsLumpkin R, Grodsky SA, Centurioni L, Rio MH, Carton JA, Lee D
JournalJournal of Atmospheric and Oceanic Technology
Date Published2013/02
Type of ArticleArticle
ISBN Number0739-0572
Accession NumberWOS:000315197500015
Keywordsaltimeter; currents; tropical pacific; undrogued drifters; wind

Satellite-tracked drifting buoys of the Global Drifter Program have drogues, centered at 15-m depth, to minimize direct wind forcing and Stokes drift. Drogue presence has historically been determined from submergence or tether strain records. However, recent studies have revealed that a significant fraction of drifters believed to be drogued have actually lost their drogues, a problem that peaked in the mid-2000s before the majority of drifters in the global array switched from submergence to tether strain sensors. In this study, a methodology is applied to the data to automatically reanalyze drogue presence based on anomalous downwind ageostrophic motion. Results indicate that the downwind slip of undrogued drifters is approximately 50% higher than previously believed. The reanalyzed results no longer exhibit the dramatic and spurious interannual variations seen in the original data. These results, along with information from submergence/tether strain and transmission frequency variations, are now being used to conduct a systematic manual reevaluation of drogue presence for each drifter in the post-1992 dataset.

Short TitleJ. Atmos. Ocean. Technol.
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