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OCG HF Radar
To improve our understanding of the workings of the coastal ocean for a variety of environmental applications, including hurricane storm surge along the West Coast of Florida, the University of South Florida’s College of Marine Science (USF/CMS) established a real-time Coastal Ocean Monitoring Prediction System (COMPS) for the West Florida Shelf region. COMPS program observing assets consist of arrays of offshore buoys and coastal stations for surface meteorology and in-water measurement of temperature, salinity, currents, and sea level; along with several High Frequency (HF) Radar sites for offshore surface-current velocity field measurements. Commercially available CODAR and WERA HF Radar systems have been in operation for nearly eight years in this challenging region of limited beach availability/access, low wave energy, severe weather, and frequent lightning activity. Along with the coastal ocean observations is a coordinated program of coastal ocean modeling.
Quantitatively predicting Florida's coastal ocean water properties is dependent on the merging of quality observations with models. The underpinnings are the coastal ocean circulation since the currents are what deliver nutrients from the deep-ocean and the estuaries to the shelf, thereby fueling primary productivity and initiating the complex biological and chemical interactions resulting in the shelf ecology. Commercial and recreational fisheries depend on this as do blooms of harmful red-tide algae. Similarly, safe and efficient maritime commerce depends on our ability to specify currents, sea level, and sea state on the basis of the ocean and atmosphere interactions. Inundation by hurricane storm surge is also matter of great public concern.
High frequency (HF) radars provide a means for mapping fields of surface velocity vectors by using the Doppler shift in frequency for radio frequency waves scattered off of surface gravity waves. From these returns a set of radial velocity components is calculated, and given two independent systems, deployed at two different locations along the shoreline, these radial velocity components may be combined to give a field of surface velocity vectors.
Two types of systems are available: either direction finding with a compact antenna system or beam forming with a linear antenna array. Direction finding HF-radars, such as the commercially available CODAR, uses a single transmit antenna and a single receive antenna. The transmissions are Omni directional, and the receive antenna senses returns along radial directions at fixed angular and radial distances.
Phased array HF-radar, such as the commercially available WERA, uses a 4 antenna transmit array and a 12-16 antenna receive array positioned at close intervals along the beach, to record the backscattered radio wave signals. By virtue of the increased number of antennas, it can operate both in a via direction finding and directional beam forming mode.
Existing USF/CMS Combined CODAR and WERA HF Network
COMPS presently operates four long range CODAR systems [Redington Shores, Venice, Naples, and Marathon, Florida], as well as two WERA systems [Ft De Soto, Venice] on the West Florida Shelf (WFS). The USF CODAR HF-radar systems operate at 4.90 MHz and the WERA HF-radar systems operate between 12.23 – 13.20 MHz. The actual WERA transmit frequency and bandwidth is determined by first sweeping the entire operational band prior to each acquisition via WERA’s “Listen before Talk Mode” software to determine the region of lowest noise level and corresponding bandwidth. Hourly data from each site is pulled via scripting to a central processing station located at USF/CMS in St. Petersburg, Florida, where the data is processed and web served.
Redington Shore (RdSr) Site CODAR Notes: The Long Range CODAR site is located at 18200 Gulf Boulevard, Redington Shores, Florida (27° 49.937' N, 82° 50.032' W) within the Pinellas County, Florida Redington Shores Beach Access Park. Offshore sea surface current speed and direction radial data is provided hourly via a dedicated cellular modem to USF/CMS. This site became operational on 9/24/03.
Venice (Veni) Site CODAR Notes: The site is located at 1200 South Harbor Drive, Venice, FL (27° 04.655' N, 82° 27.096' W) at the U.S. Coast Guard Auxiliary Station number 86. Offshore sea surface current speed and direction radial data is provided hourly via a dedicated cellular modem to USF/CMS. This site became operational on 4/27/04.
Naples (Napl) Site CODAR Notes: The site is located at 1301 Gulf Shore Boulevard N, Naples, FL (26° 09.729' N, 81° 48.632' W) within the City of Naples' Loudermilk Park. Offshore sea surface current speed and direction radial data is provided hourly via a dedicated cellular modem to USF/CMS. Initial operation commenced on 12/22/04 with final operation 4/20/05.
Ft De Soto Park/Tierra Verde Site WERA Notes: The 12 RX antenna WERA site is located at the North Beach Pavilion at Ft DeSoto Park (27° 38.16' N, 82° 44.30' W). Offshore sea surfacecurrent speed and direction radial data is provided hourly via a dedicated cellular modem to USF/CMS. This site became operational on 6/05/10.
Venice Site WERA Notes: TThe 12 RX antenna WERA site is Co-located along with the USF CODAR site at the U.S. Coast Guard Auxiliary Station number 86. Offshore sea surface current speed and direction radial data is provided hourly via a dedicated cellular modem to USF/CMS. This site became operational on 6/13/10.
Marathon (MARA) Site CODAR Notes: The site is located at 56200 Overseas Highway, Marathon, FL 33050 (24° 44.417' N, 80° 59.000' W) within Curry Hammock State Park, Monroe County. Offshore sea surface current speed and direction radial data is provided hourly via a dedicated cellular modem to USF/CMS. This site became operational on 12/20/2019.
Ongoing Discussion/Future Plans
Continuous HF Radar operation on the WFS has had its challenges. After several years of continuous system operation, it became becoming apparent that 5 MHz may not be the optimal choice as an HF Radar operational frequency for the WFS considering its low current/wave climate, frequent lightning related ambient noise effects, and increased traffic in and around the 5 MHz band. For that reason, the operational frequency of the WERA HF Radar sites was set at nominally at 12.7 MHz, with the site locations chosen to be within our existing CODAR HF Radar footprint as shown in Figure 1. This established an HF Radar test-bed, focused on the region between Venice and the mouth of Tampa Bay in which we routinely relative performance between different measurement systems at different frequencies, each overlooking an array of in situ water column velocity measurements by COMPS buoy-mounted ADCPs.
In response to a National Academies of Sciences, Engineering, Medicine (NASEM) Gulf Research Program (GRP) goal to increase the understanding and prediction of the Gulf of Mexico Loop Current System (GOM LCS), three additional HF Radar CODAR SeaSonde Ocean Surface Current Measurement systems are being installed covering the Straits of Florida region from the Florida Keys to Cuba along with data integration into our existing COMPS/Ocean Circulation Laboratory (OCL) HF Radar network. The requirement for these additional HF Radar systems stem from knowledge gaps in understanding the controls on the GOM LCS and the need for real-time surface current data for assimilation in numerical circulation models of the of the GOM and its inflow and outflow regions between Mexico and Cuba and between Florida and Cuba, respectively. These three HF Radar sites will be located at Fort Jefferson/Dry Tortugas National Park, Key West, Florida and Marathon, Florida with the two Florida Keys locations overlooking the Straits of Florida. The Marathon HF Radar site became operational on 12/20/2019 with the remaining two lower keys sites awaiting final permits prior to installation.
The COMPS observing and modeling system has benefited from funding over a variety of sources, beginning with the USGS at its inception, continuing with MMS, ONR and NOAA support, along with that from the State of Florida through USF.
Operational and Maintenance funding for the West Florida Coast HF Radar sites has been provided through various NOAA programs including the NOAA IOOS SECOORA program and the USF/CMS. WERA equipment additions were made possible through USF internal R&D funds. Site operations occur through collaborative efforts between the COMPS program and Pinellas County, Florida, the City of Naples, Florida, and the U.S. Coast Guard Auxiliary Station Number 86 in Venice, Florida.
Funding for the lower Florida Keys HF Radar sites is provided via a NASEM/GRP competitively awarded grant with operation for the Marathon HF Radar site through a collaborative effort between the COMPS program and Curry Hammock State Park. Local project support for the Marathon site was provided by the Keys Marine Laboratory, Arlington Electric South, Inc. and Keys Community Construction, LLC.