Assessment of HF Radar for Significant Wave Height

Determination

Desmond Power

VP, Remote Sensing, C-CORE

Agenda

• Study Rationale

• Technology Overview

• Technology Assessment for CNLOPB

• Proposed ‘Go Forward’

Study Rationale

• Sikorsky S-92A rated to Sea State 6 (4-6m)

• No flights above SS6

• Sea state measurements available at rigs and on-shore

• No sea state measurement between platforms and shore

– Networks of wave buoys are rather impractical considering the required areal coverage

– Is there an alternative technology?

HF Radar Technology

• Crombie observed peaks in HF radio wave echoes in 1955

– Observed Doppler shift in the radar echo

– Concluded it was from ocean gravity waves

• Studies in the 1970s showed relationship between radio signal backscatter and characteristics of gravity wave

• Surface currents, surface winds and surface waves could be derived

Study Objectives

• Investigate HF radar technology for measuring wave heights

• Demonstrate that technology works

– Can it work over the extended range required, >300km?

– Can it measure Sea State 6 and beyond?

• Use existing facility to baseline the capability

– What is the system configuration?

– What are the power levels?

– Where should the system be installed?

– What type of information can be supplied?

HF Radar Technology Overview

The Signal

(from University of Hamburg)

Doppler Spectrum

Doppler Frequency

No

rmal

ize

d P

ow

er S

pe

ctra

l De

nsi

ty

HF Radars are known for Current Mapping Capability

C-CORE Research (Howell and Walsh, 1993) from Canadian Atlantic Storms Program (CASP, 1986)

Cape Race, Cape Bonavista DND Radars

200 meter contour

HF ROSA

• High Frequency Radar Ocean Surface Applications

• Objective: Real time knowledge of ocean surface conditions

• Argentia test site looks into Placentia Bay

• Project Partners – MUN Faculty of

Engineering

– MUN Physics and Physical Oceanography

– Northern Radar Inc

HF ROSA 2012 Field Program Placentia Bay

HF ROSA 2012 Field Program Placentia Bay

Transmit Antenna Array

Receive Antenna Array

Currents from HF ROSA

Waves from HF ROSA

Technology Assessment

Sample WERA/Northern Radar Radar Spectra from Placentia Bay

11.7 km 59.7 km

Waves from HF ROSA

Buoy Measured Waves: 2.53 m

Buoy Measured Waves: 1.28 m

Significant wave heights from the radar are within about ±0.25 m of the buoy readings

Radar is here

Maximum Range Analysis

• 13.385 MHz

– 10 Watts

– SWH = 2.3 m

– Range = 60 km

– Measured Second Order has 10 dB SNR

• Can radar measure Sea State 6?

• What is radar range at Sea State 6?

• Use 7.7 metres as benchmark (~30% above SS6)

Maximum Range Analysis

• 13.385 MHz

– 100 Watts

– 7.7 m waves

– Modeled Second Order has 10 dB SNR

• 150 km when winds are along the radar look

• 110 km when winds are across the radar look

• 10 MHz

– 100 Watts

– 7.7 m waves

– Modeled Second Order has 10 dB SNR

• 170 km when winds are along the radar look

• 120 km when winds are across the radar look

Coverage for 150km Radars

~150 km

~150 km

HF Oceanographic Radar

• Recommend operating in 10 MHz Frequency Range

• Antennas

– Receive antenna ~6m high guyed monopole

– Array of 12 elements

– Shore based 165 m long

– Production platform based ~100 m (7 elements), mounted underneath topsides

• 100 Watt transmitter

Coastline Concept

TX Array

RX Array

Platform Concept

Phase 2 Objectives

• Install a single dedicated shore-based HF Radar facility

• Facilitate access to data in near-real-time

• Operate facility for one year

• Demonstrate the performance of the radar – Does it give the information you need

• Reliably

• Timely

• Accurately

– Is this better than what we had?

– Does this system introduce other problems?

• Interface with industry to integrate wave height data

• Make recommendations for a system that covers the full flight path from shore to platforms (Phase 3)

Prospective Site – Bear Cove Point

Prospective Site – White Hills