A decade of IMOS HF ocean radar surface current data

Observations of coastal ocean surface currents with high spatial and temporal resolution provide a critical tool for understanding physical and ecological processes, and for validating ocean circulation models. Despite this, few observation techniques can provide the necessary data. High-Frequency Radar (HFR) are one of the few systems that can provide both high temporal and spatial resolution of surface currents. HFR relies on Doppler backscatter observations in the HF (radio wave) portion of the electromagnetic spectrum (3-50 MHz) to map near-surface currents on hourly timescales up to several hundred kilometres offshore. The Integrated Marine Observing System (IMOS) Ocean Radar facility has deployed and managed HFR systems around the coastline of Australia since 2010, resulting in more than a decade of freely available real-time and quality-controlled data around Australia. The long-term gridded hourly HFR data compliment more traditional observations such as moorings as the dataset enables investigations of event scale processes (order of kilometres / hours) all the way to longer and wider scales spanning from shallow water to beyond the continental shelf, over more than a decade. This talk will use the dataset to illustrate such processes as the influence of the sea breeze on surface currents, passage of a tropical cyclone, the generation and persistence of sub-mesoscale eddies, and the cross-shelf migration of boundary currents. Examples will be shown for East Australian Current, Bonney coast upwelling, Leeuwin and Capes Current structures from the southwest and Ningaloo regions of Western Australia.