Seminario: Submesoscale coastal surface circulation studies using high-frequency radars
Start: 23/01/2020 10:00 - End: 23/01/2020 11:00Place: Sala de seminarios, IMEDEA
Submesoscale coastal surface circulation studies using high-frequency radars
Speaker: Sung Yong Kim, Ph.D., Prof. (Korea Advanced Institute of Science and Technology -KAIST-)
Summary: This talk presents various aspects of coastal surface circulation based on multiyear
observations of high-frequency radar-derived surface currents off the U.S. West
coast. The dynamics of the surface currents are governed by tides, winds, Coriolis force,
low-frequency pressure gradients (less than 0.4 cycles per day (cpd)), and nonlinear
interactions of those forces. Alongshore surface currents show poleward propagating signals
with phase speeds of O(10) and O(100 to 300) km day−1 and time scales of 2 to 3 weeks.
The signals with slow phase speed are only observed in southern California. It is
hypothesized that they are scattered and reflected by shoreline curvature and bathymetry
change and do not penetrate north of Point Conception. The seasonal transition of
alongshore surface circulation forced by upwelling-favorable winds and their relaxation is
captured in fine detail. Submesoscale eddies, identified using flow geometry, have Rossby
numbers of 0.1 to 3, diameters in the range of 10 to 60 km, and persistence for 2 to 12 days.
The HFR surface currents resolve coastal surface ocean variability continuously across
scales from submesoscale to mesoscale (O(1) km to O(1000) km). Their spectra decay with
k−2 at high wave number (less than 100 km) in agreement with theoretical submesoscale
spectra below the observational limits of present-day satellite altimeters. In addition, the
diagnostic characterizations of recent submesoscale observations of surface currents and
chlorophyll concentrations are discussed.
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