High Frequency Radar Observing Systems in SEACOOS: 2002-2007 Lessons Learned

From 2002-2007, the Southeast Coastal Ocean Observing System (SEACOOS) deployed high frequency (HF) radars to overlook several venues stretching from the West Florida Shelf to the North Carolina Shelf. Based on extensive deliberations within SEACOOS, we decided to assess the two differing types of coastal ocean current radars within the southeast that were on the commercial market. The long-range SeaSondes (SS) were deployed to sense surface currents at hourly intervals and a 6 km resolution along the West Florida Shelf and the North Carolina Shelf. The medium and long-range Wellen Radars (WERA) were deployed along the Florida Straits and along the South Atlantic Bight with spatial resolutions of 1.2 to 3 km sampling at time scales of minutes. A common theme in these deployments was to sense the Loop Current, Florida Current and the Gulf Stream, which transport heat poleward as part of the gyre circulation.Several lessons were learned as part of these deployments, such as the need to protect against lightening strikes and the challenge of providing robust communication links between the remote sites and a central hub to make the data available in near real-time. Since states in the southeast and surrounding the Gulf of Mexico are prone to the passage of hurricanes, surface current and wave measurements during hurricanes are invaluable for improving storm surge and inundation models that are now being coupled to surface waves. In addition, significant wave heights (and directional surface wave spectra) are critical in the model assessment. Data quality and accuracy of the surface current and wave fields remain a central issue to search and rescue and safe maritime operations and to understanding the limitations of these radar systems. As more phased array systems (i.e., WERAs) are deployed for surface current and wave measurements, more attention needs to be placed on the interoperability between the two types of systems to insure the highest quality data possible is available to meet applied and operational goals. To insure the highest quality data possible, a full-time technician and a half-time IT specialist are needed for each installation as well as access to spares to keep these systems running consistently and to make quality observations available in near real-time.

Download Full-text

High-Frequency Radar Mapping of Surface Currents Using WERA

Journal of Atmospheric and Oceanic Technology ◽

10.1175/jtech1985.1 ◽

2007 ◽

Vol 24 (3) ◽

pp. 484-503 ◽

Cited By ~ 53

Author(s):

Lynn K. Shay ◽

Jorge Martinez-Pedraja ◽

Thomas M. Cook ◽

Brian K. Haus ◽

Robert H. Weisberg

Keyword(s):

Time Series ◽

High Frequency ◽

Tidal Currents ◽

Tropical Storm ◽

Surface Velocity ◽

Surface Currents ◽

West Florida Shelf ◽

The West ◽

Florida Shelf ◽

East West

Abstract A dual-station high-frequency Wellen Radar (WERA), transmitting at 16.045 MHz, was deployed along the west Florida shelf in phased array mode during the summer of 2003. A 33-day, continuous time series of radial and vector surface current fields was acquired starting on 23 August ending 25 September 2003. Over a 30-min sample interval, WERA mapped coastal ocean currents over an ≈40 km × 80 km footprint with a 1.2-km horizontal resolution. A total of 1628 snapshots of the vector surface currents was acquired, with only 70 samples (4.3%) missing from the vector time series. Comparisons to subsurface measurements from two moored acoustic Doppler current profilers revealed RMS differences of 1 to 5 cm s−1 for both radial and Cartesian current components. Regression analyses indicated slopes close to unity with small biases between surface and subsurface measurements at 4-m depth in the east–west (u) and north–south (υ) components, respectively. Vector correlation coefficients were 0.9 with complex phases of −3° and 5° at EC4 (20-m isobath) and NA2 (25-m isobath) moorings, respectively. Complex surface circulation patterns were observed that included tidal and wind-driven currents over the west Florida shelf. Tidal current amplitudes were 4 to 5 cm s−1 for the diurnal and semidiurnal constituents. Vertical structure of these tidal currents indicated that the semidiurnal components were predominantly barotropic whereas diurnal tidal currents had more of a baroclinic component. Tidal currents were removed from the observed current time series and were compared to the 10-m adjusted winds at a surface mooring. Based on these time series comparisons, regression slopes were 0.02 to 0.03 in the east–west and north–south directions, respectively. During Tropical Storm Henri’s passage on 5 September 2003, cyclonically rotating surface winds forced surface velocities of more than 35 cm s−1 as Henri made landfall north of Tampa Bay, Florida. These results suggest that the WERA measured the surface velocity well under weak to tropical storm wind conditions.

Download Full-text

Evaluation of Satellite-Derived SST Products in Identifying the Rapid Temperature Drop on the West Florida Shelf Associated With Hurricane Irma

Marine Technology Society Journal ◽

10.4031/mtsj.52.3.7 ◽

2018 ◽

Vol 52 (3) ◽

pp. 43-50 ◽

Cited By ~ 5

Author(s):

Yonggang Liu ◽

Robert H. Weisberg ◽

Jason Law ◽

Boyin Huang

Keyword(s):

Temperature Drop ◽

Coastal Ocean ◽

Sea Surface ◽

West Florida Shelf ◽

The West ◽

Florida Shelf ◽

Time Period ◽

Rapid Temperature ◽

Ocean Observations ◽

Hurricane Irma

AbstractSatellite-derived daily sea surface temperature (SST) products are compared with moored SST observations on the West Florida Shelf during the time period of Hurricane Irma. Most of the SST products compare reasonably well with the moored data at the location of 25-m depth, where SST dropped by about 1°C after the hurricane passage. However, most of the SST products did not show the rapid SST drop at the location of 50-m depth where the surface water was cooled by about 4°C within 1 day in response to the hurricane passage. This finding has important implications to air-sea interaction studies and hurricane simulations, in which SST data play an important role. The limitations of the popular satellite products call for additional coastal ocean observations as well as proper inclusion of the real-time observations in satellite-derived products.

Download Full-text

A coastal ocean observing system and modeling program for the West Florida Shelf

OCEANS '02 MTS/IEEE ◽

10.1109/oceans.2002.1193324 ◽

2003 ◽

Author(s):

R. Weisberg ◽

Ruoying He ◽

M. Luther ◽

J. Walsh ◽

R. Cole ◽

...

Keyword(s):

Coastal Ocean ◽

West Florida Shelf ◽

The West ◽

Florida Shelf ◽

Ocean Observing

Download Full-text

HF Radar Performance in a Low-Energy Environment: CODAR SeaSonde Experience on the West Florida Shelf*

Journal of Atmospheric and Oceanic Technology ◽

10.1175/2010jtecho720.1 ◽

2010 ◽

Vol 27 (10) ◽

pp. 1689-1710 ◽

Cited By ~ 51

Author(s):

Yonggang Liu ◽

Robert H. Weisberg ◽

Clifford R. Merz ◽

Sage Lichtenwalner ◽

Gary J. Kirkpatrick

Keyword(s):

Coastal Ocean ◽

Low Energy ◽

Ocean Dynamics ◽

Hf Radar ◽

Limiting Factors ◽

West Florida Shelf ◽

The West ◽

Florida Shelf ◽

Significant Wave ◽

Energy Environment

Abstract Three long-range (5 MHz) Coastal Ocean Dynamics Application Radar (CODAR) SeaSonde HF radars overlooking an array of as many as eight moored acoustic Doppler current profilers (ADCPs) have operated on the West Florida Shelf since September 2003 for the purpose of observing the coastal ocean currents. HF radar performance on this low-energy (currents and waves) continental shelf is evaluated with respect to data returns, the rms differences between the HF radar and the ADCP radial currents, bearing offsets, and radial velocity uncertainties. Possible environmental factors affecting the HF radar performance are discussed, with the findings that both the low-energy sea state and the unfavorable surface wave directions are the main limiting factors for these HF radar observations of currents on the WFS. Despite the challenge of achieving continuous backscatter from this low-energy environment, when acquired the data quality is good in comparison with the ADCP measurements. The rms differences range from 6 to 10 cm s−1 for hourly and from 3 to 6 cm s−1 for 36-h low-pass-filtered radial currents, respectively. Bearing offsets are in the range from −15° to +9°. Coherent variations of the HF radar and ADCP radial currents are seen across both tidal and subtidal frequency bands. By examining the HF radar radial velocities at low wave energy, it is found that the data returns decrease rapidly for significant wave heights smaller than 1 m, and that the rms differences between the HF radar and ADCP radials are degraded when the significant wave height is smaller than 0.3 m.

Download Full-text