Getting a feel for HF coastal radar

Transcription

1 Monitoring enhancement Getting a feel for HF coastal radar Pia Andersson Philip Axe

2 In the early days The influence of ocean waves on HF radar backscatter was reported by Crombie in He examined the backscatter of a MHz signal, and noticed the peak energy in the reflected signal was constant at 0.38 Hz. He proposed that this dominant reflected component was probably due to back scattering of the radar signal by water waves. The Backscatter is caused by Bragg scattering. 1974, Stewart and Joy reported on using HF radar for measurements of ocean currents.

3 Main systems on the market Codar Wera Pisces Japanese system Different combinations of system

4 Where in operation? JAMES COOK UNIVERSITY JCU Headquarters TURQUOISE COAST TURQ ROT ROTTNEST Phased Array WERA CAPRICO RN Bunker COFFS GROUP HARBOUR SOUTH AUSTRALIAN GULFS SAG CBG COF BONNEY COAST BONC Crossed Loop SeaSonde There are two radar stabons at each site UNIVERSITY of TASMANIA UTAS

5 What can HF radar provide us with? Currents, waves, ship tracking, wind High resolution in space and time, near real time H. Roarty, Rutgers University

6 Translated into usefulness Areal near real time current observations are likely to promote research and development related to fish larvae / nutrients / bacteria transports, in/outflow, the spread of alien species, improve oceanographic models and lead to the better understanding of ocean and coastal sea processes.

7 Translated into usefulness Data are needed for safe and efficient ship routing in narrow areas of high traffic such as in the northern Kattegat, Danish Straits, Bornholm Strait and the Gulf of Finland. Access to high quality, spatially resolved current information is critical both for effective oil spill containment and greatly increases the chances for successful outcomes of search and rescue operations. Combining data from models and observations will reduce the search area in rescue operations and make planning and combat of oil spill operations more efficient.

8 Up: Instantaneous screen shot from MarineTraffic.com. Down: illegal oil discharges observed, HELCOM MARIS Baltic shipping density observed by HELCOM AIS during one week in Busiest routes highlighted in yellow (HELCOM, 2009)

9 Example of a successful application of BADIS, to recover a small sports boat in the eastern Skagerrak adrift for up to 22 hours.

10 Needs / Shortcomings No nation wide real inclusion of currents measured in monitoring programs today It is difficult to resolve the complex currents in the Skagerrak / Kattegat with (un-validated) large scale models. The typical length scale (first order Rossby radius) is about 5 km. As a result, eddies, meanders and other chaotic features in surface currents are small. It is both difficult to observe them with buoys and ships, and difficult to describe their position and development accurately in models.

11 Ups and downs with HF radar Tradeoffs: due to links between range, resolution and bandwidth. Ex: 1 km grid cell => max 50km range. Downs: Not off the shelf system, high technical and signal processing expertise needed, expensive systems, bandwidth limitations, restricted access to costal sites, tuning of system towards mainly one of the different interest areas (curr, wave, ships), surface measurements, outer sea or coast angle, low salinity= poor data recovery. Ups: coverage in time and space, near real time, collaborations, many end users, cost per datapoint is low, land based is good!

12 Mal Heron, Photos by permission: The Townsville Bulletin ACORN Land-based is good

13 SMHI aim Swedish Environmental Protection Agency commissioned a workshop 2010 organized by SMHI with the aim: Nordic cooperation in the field of oceanographic (coastal) radar with the ultimate aim of establishing a Nordic network covering (initially) the shared waters of the Skagerrak and Kattegat. The other area of interest are selected focal areas with higher resolution Cooperation is now proceeding with support from HaV Other Countries with expressed will to cooperate are Germany & Poland. There are a few coming funding possibilities within BONUS and FP7 Besides national and international cooperation, SMHI aims for high standard, useful and efficient monitoring programs, data availability, assimilation and validated models

14 Summary / Motivation of including this talk today? Currents mentioned in MSFD (evaluations to be made within the MSFD assessments) & if we are to couple measurements & models in future monitoring programs we need validation and assimilation and better hydrographic models (coupled to BGC models). Support to ecosystem management Achieving the goal of Good Environmental Status requires detailed knowledge of the pressures on the region, including the nutrient (and toxic substance) inputs from adjacent sea areas. Estimates of nutrient loading from different sea areas should be improved, by using measured data and validated three dimensional coupled ecosystem models. Using observed currents to constrain and validate the models would increase the reliability of the (nutrient) flux estimates. A better understanding of the drift of harmful algal blooms, or the larvae of invasive species would also facilitate regional ecosystem management. The ability to trace and predict the spread of harmful organisms should lead to improved early warning of potential problems and may help shellfish producers optimize harvesting. In the case of land-based fish farms, this may even allow managers to close water intakes in good time to avoid contamination. Thank you for your time