- Количество слайдов: 14
High Frequency Radars: Wind, Waves and Currents Oh My! L. K. Shay 1, J. Martinez-Pedraja 1, B. K. Haus 1 , Brad Parks 1, Peter Vertes 1, Lew Gramer 2, and J. Brewster 1 1 Division of Meteorology and Physical Oceanography, RSMAS 2 Ocean 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
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 Key Systems 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 2 nd -order to 1 st-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 WERA System / Crandon Park →
Performance and EFS Measurement Grid Frances and Wilma-Longest Down Time - Domain and Distribution of Good Data
Florida Current Variability 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.
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 Directions Wind Speeds
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.