AWIPS-2 HF Radar Sea-Surface Current Product By Ross Van Til Contributions by: Nicole Kurkowski, OS&T Dr. Pablo Santos, WFO Miami Dr. Jack Harlan, NOAA IOOS Dr. Brian Haus, U of Miami

Learning Objectives Understand basics of how HF coastal radars retrieve sea-surface current data Grasp the areal coverage HFRs provide Characterize the spatial and temporal resolution of sea-surface current data provided in AWIPS-2 Classify the types of currents represented in the data Summarize operational applications

Performance Objectives Access sea-surface current data in AWIPS-2 Manipulate the AWIPS display to optimally view/interpret the data Use data appropriately to enhance marine products and services

What is HF Radar Operates in high-frequency radio portion of EM spectrum Wavelengths in the m range

Types of HF Radar  Compact antenna/Direction Finding (CODAR) 95% of US HFRs Range of up to 200 km Broad beam Antennae occupy small amount of space

Types of HF Radar  Phased-array/Beam forming (OSCR,WERA) Range of km Narrow beam Better temporal, spatial resolution Capable of resolving complex current fields Can better measure waves

How HF Radar Works

What HF Radars Provide Sea-Surface Currents (speed and direction)  Range = 1 to 200 km  Spatial resolution = 0.2 to 6 km  Temporal resolution = 10 to 60 min  Velocity accuracy = 5 to 10 cm/s  Directional accuracy = 10 degrees  Depth of measurement = 1-2 m Surface wind direction and speed can also be measured Some types (OSCR, WERA) can also measure wave height, period, and wave directional spectra

Surface Currents and Wave Forecasting Following Current

Surface Currents and Wave Forecasting Opposing Current

HF Radar Network 11 IOOS Regional Associations serve the entire US Coastline, including the Great Lakes, Caribbean, and Pacific Territories

CONUS HF Radar Coverage

OCONUS HF Radar Coverage

Sea-Surface Current Data in AWIPS-2

Accessing the Data in AWIPS-2

Preferred Data Combination?

Sampling Current Speed

AWIPS-2 Data Loop

AWIPS-2 Data Characteristics Temporal Resolution = hourly One hour average centered on hour Spatial Resolution varies from 1km to 6km Data is spatially averaged Data that does not pass a QC check will not be displayed (may see holes in data) Areal Coverage = good portion of contiguous US and some OCONUS

Daytime vs. Nightime % good data

Other Considerations Range/coverage reduced in areas of strong winds and high waves Interference from distant sources can occur Need “deep” water

Oceanic Currents

Tidal Currents

Wind-Driven Currents

Operational Applications Wave Forecasting Surface currents can significantly alter wave properties (steepness/height)  Opposing current increases steepness/height  Following current decreases steepness/height Surface currents can effect on wave growth rate Compare to RTOFS current data which is input to Nearshore Wave Prediction System (NWPS)

Other Operational Applications Rip current prediction Trajectory analysis for oil spill and search and rescue situations Water quality monitoring Harmful Algal Bloom Forecasts Fisheries and Ecosystem Management

Summary Mature technology for measuring ocean current velocities over large coastal areas Numerous important applications Hourly, near-real-time Spatial resolution in AWIPS-2 = 1-6 km Up to 200 km range Performs better during daytime

References and Data Sources on Web IOOS HF Radar Page: NDBC Real-Time Data: CORDC Site (real-time data and much more)