L. K. Shay1, J. Martinez-Pedraja1, B. K. Haus1 , Brad Parks1, Peter Vertes1, Lew Gramer2, and J. Brewster1

1Division of Meteorology and Physical Oceanography, RSMAS2Ocean Chemistry Division, AOML-NOAA

Goal: To improve our understanding of surface processes and their linkages to atmospheric and oceanic boundary layer processes.

http://isotherm.rsmas.miami.edu/~nick

High Frequency Radars: Wind, Waves and CurrentsOh My!

Introductory Remarks:

HF radar capabilities in mapping surface current regimes with submesoscale variability over short time and space scales.

WEllen RAdars (WERA) in phased array mode with cells of about 1 km over a range of ~80 to 90 km (Research Phase).

In support of SEA-COOS, Monitoring Phase provides radial and surface cur rent vector fields at 2 km intervals each hour.

WERAs are now deployed at Key Largo, Key Biscayne, Virginia Key (12.5 MHz) and Dania Beach.

Goal: Mapping currents, waves (significant wave height, wave period, directional wave spectra ) and surface winds in the coastal ocean in real time.

Hangovers in Recent HF Radar Deployments

Objective: Extend the radar footprint of the High Frequency (HF) Radars deployed in South Florida using Wellen Radar (WERA) technology sponsored by the Southeast Atlantic Coastal Ocean Observing System.

John U Lloyd State Park and US Navy SFTF. Virginia KeySystems return data near real-time.

Unexpected Delays:1. Permits from Local and State Entities;2. Vendor Shipment of new systems; and,3. Communications at NOVA (SFTF) and VK sites.

Four systems reporting data to RSMAS in near real time that include radial currents (combine to form vector fields), significant wave height (wave period),wind speed and direction, and directional wave spectra (Seaview software recently Installed in Nov 2008).

Radar Power (Doppler) Spectrum: Bragg Backscatter (Neptune Radar Ltd, Pisces)

Wind (short wave) direction measured from magnitude difference between the two blue peaks. Here wind is blowing towards the radar.

Hs can be derived from scaled ratio of 2nd -order to 1st-

order peaks from a single

radar site.

Full directional spectra obtained from Iterative inversion

of Doppler spectra to match surface

Wave spectrum. Doppler spectra must be

observed from two overlapping stations (Wyatt 1990)

Specifications of Radar

Resolution of Current Velocity versus Averaging Time@ different centre frequencies

0

5

10

15

20

25

30

2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 32

Time in Minutes

Re

so

luti

on

in

cm

/se

c

fo = 5 MHz

10 MHz

15 MHz

20 MHz

30 MHz

WERA System / Crandon Park →

Range of 1-st order beam versus Frequency

y = 1354,5x-0,9781

R2 = 0,867

0,00

25,00

50,00

75,00

100,00

125,00

150,00

175,00

200,00

225,00

250,00

0,00 5,00 10,00 15,00 20,00 25,00 30,00 35,00 40,00 45,00 50,00

Frequency in MHz

Beam

form

ed

Ran

ge i

n k

m

08th of May 2006Tests with different WERA installations all with linear array (12 or 16 antennas)

WERA Range (km) 80-120 Resolution (km) 1.200 Depth of Measurement (m) 0.75 Type FMCW Accuracy Current Speed (cm s-1) 5 Vector Direction (o) 3 Operating Frequency (MHz) 16.4 Receive Antennae 16 Frequency Scanning (KHz) 250 Peak Power (W) 30 Average Power (W) 30 Baseline Distance (km) 55

Table 1: WERA Operating parameters in SE Florida.

Performance and EFS Measurement Grid

Frances and Wilma-Longest Down Time - Domain and Distribution of Good Data

FC axis exceeds 3 knots!

FC core exceeds 40-km in cross-shelf direction.

FC cyclonic shear zone with strong gradient.

Mesoscale meander of FC axis.

FC extends more than 40 km from the shelf.

FC flow generally weaker with a narrower core.

FC cyclonic shear with weak gradient.

Florida Current Variability

Submesoscale Vorticies (Jan 05):

Signal to Noise Ratio’s-Four Sites

Domains from all four HF radar sites

WERA (blue) and 14-m (black)ADCP Record: Submesoscale Event 2

Dec 04 – Feb 05

Wind Directions and Speed Comparisons at Fowey Rocks During Jeanne:24-25 Sept 2004

Wind Speeds Wind Directions

Directional Wave Spectra During Jeanne (04)(Processed by Seaview Remote Sensing Systems-UK

SECOORA/GCOOS Gap Analysis: HF Radar Network For IOOS

Summary of Progress from ~6 Years of Measurements:

COOS - All working together to achieve a common goal of improving ocean observing in the state (complementary strengths).

State support extended footprint northward, need to• Improve signals at VK and DB; • Time intervals-WERA is FMCW system (256, 512, 1024…)

represented 2.2, 4.4, 9 min... samples;• Improve Hs and wave spectra algorithms (compare to wave buoy

measurements-2048 samples);• Linkages to marine surface winds and waves-response to

understand surface winds;• Wind-driven surface velocity pushes water toward the coast which

causes the water to rise to evaluate storm surge models; and,• Radar sites must be hardened to withstand hurricane conditions

with its own power and built-in redundancy.