Surface circulation in Block Island Sound and adjacent coastal and shelf regions: A FVCOM-CODAR comparison

Abstract

CODAR-derived surface currents in Block Island Sound over the period of June 2000 throughSeptember 2008 were compared to currents computed using the Northeast Coastal Ocean Forecast System (NECOFS). The measurement uncertainty of CODAR-derived currents, estimated using statistics of a screened nine-year time series of hourly-averaged flow field, ranged from 3-7 cm/s in speed and 4°-14° in direction. The CODAR-derived and model-computed kinetic energy spectrum densities were in good agreement at subtidal frequencies, but the NECOFS-derived currents were larger by about 28% at semi-diurnal and diurnal tidal frequencies. The short-term (hourly to daily) current variability was dominated by the semidiurnal tides (predominantly the M 2 tide), which on average accounted for ~87% of the total kinetic energy. The diurnal tidal and subtidal variability accounted for ~4% and ~9% of the total kinetic energy, respectively. The monthly-averaged difference between the CODAR-derived and model-computed velocities over the study area was 6 cm/s or less in speed and 28° or less in direction over the study period. An EOF analysis for the low-frequency vertically-averaged model current field showed that the water transport in the Block Island Sound region was dominated by modes 1 and 2, which accounted for 89% and 7% of the total variance, respectively. Mode 1 represented a relatively stationary spatial and temporal flow pattern with a magnitude that varied with season. Mode 2 was characterized mainly by a secondary cross-shelf flow and a relatively strong along-shelf flow. Process-oriented model experiments indicated that the relatively stationary flow pattern found in mode 1 was a result of tidal rectification and its magnitude changed with seasonal stratification. Correlation analysis between the flow and wind stress suggested that the cross-shelf water transport and its 3 temporal variability in mode 2 were highly correlated to the surface wind forcing. The mode 2 derived onshore and offshore water transport, and was consistent with wind-driven Ekman theory.The along-shelf water transport over the outer shelf, where a large portion of the water flowed from upstream Nantucket Shoals, was not highly correlated to the surface wind stress.

Simulation of Wave‐Current Interactions Under Hurricane Conditions Using an Unstructured‐Grid Model: Impacts on Ocean Waves

“…Validation of storm-induced currents is also important, because our focus is wave-current interactions and their impacts on ocean waves. The performance of FVCOM in simulating ocean parameters has been investigated by many previous studies (Chen et al, 2013cHuang et al, 2008;Ji et al, 2018;Lai et al, 2015;Li et al, 2014;Qi et al, 2009;Sun et al, 2016a;Wu et al, 2010). In terms of validation for storm-induced currents, we have observations from three ADCP data sets during hurricane Bill.…”

The Effect of Wind Forcing on Modeling Coastal Circulation at a Marine Renewable Test Site

“…From this, wave speed can also be calculated [27][28][29][30]. Total surface current vector maps can be produced from at least two radar stations collecting radial components of the surface water velocity [31]. In this work, total surface currents were used to study effects of wind field resolution on coastal surface flow fields.…”

Estimation of Coastal Currents Using a Soft Computing Method: A Case Study in Galway Bay, Ireland

“…The information in the radio-wave backscatter exploited from the ocean surface is used to infer movement of the near surface layer, including parameters of surface currents, waves and winds [33][34][35][36]. Surface flow fields in the area covered by both radars were combined based on the radial current maps for at least two stations [37,38]. Measurements obtained from the HFR systems are available in near real time.…”