Abstract
New remote sensing observations that demonstrate the presence of rip current plumes in X-band radar images are presented. The observations collected on the Outer Banks (Duck, North Carolina) show a regular sequence of low-tide, low-energy, morphologically driven rip currents over a 10-day period. The remote sensing data were corroborated by in situ current measurements that showed depth-averaged rip current velocities were 20e40cm=s whereas significant wave heights were Hs 50:5e1m. Somewhat surprisingly, these low-energy rips have a surface signature that sometimes extends several surf zone widths from shore and persists for periods of several hours, which isin contrastwith recent rip current observations obtained with Lagrangian drifters. These remote sensing observations provide a more synoptic picture of the rip current flow field and allow the identification of several rip events that werenot captured by thein situ sensors and times of alongshoredeflection oftherip flowoutsidethesurfzone.Thesedataalsocontainaripoutbreakeventwherefourseparateripswereimagedovera1-kmstretchofcoast. For potential comparisons of the rip current signature across other radar platforms, an example of a simply calibrated radar image is also given. Finally,insituobservationsoftheverticalstructureoftheripcurrent flowaregiven,andathresholdoffshorewindstress(.0:02m=s 2 )isfoundto preclude the rip current imaging. DOI: 10.1061/(ASCE)WW.1943-5460.0000229. © 2014 American Society of Civil Engineers. Author keywords: Rip currents; Radar; Surf zone; Nearshore hydrodynamics.
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