Ocean buoys aren’t glamorous, seemingly doing little more than bobbing about on the waves. However, they play a vital part in collecting data about what is happening in and above the oceans. That information is needed for weather forecasting and climate modelling as well as by scientists seeking to better understand ocean processes.
Although satellites provide global coverage of the oceans, the errors in such measurement are usually high, points out P.N. Vinayachandran, an oceanographer at the Indian Institute of Science in Bangalore. Ocean buoys, when available, supply much more accurate data that is invaluable. Besides, buoys can be equipped to make measurements below the ocean surface, which satellites cannot do.
The National Institute of Ocean Technology (NIOT) in Chennai has been indigenising different sorts of ocean buoys. It designs these buoys, undertakes their final integration and testing, deploys them out in the ocean and then maintains them in working condition.
The Met. ocean buoys carry sensors that measure atmospheric parameters (such as wind speed and atmospheric pressure) as well as key ocean data (like sea surface temperature and speed and direction of ocean currents). There are buoys that are equipped to make measurements below the ocean surface to a depth of 500 metres. Tsunami buoys can, as their name suggests, pick up signs of an oncoming tsunami well before those giant waves reach shore. The data from these buoys is relayed back via satellite links.
Indigenising the buoys is not just about lowering their cost, according to the Institute’s director, M.A. Atmanand. “With our own design, we can customise them to meet specific requirements and do not have to rely on anyone else for troubleshooting problems that arise.”
Last year, the NIOT tested a drifting buoy that it had developed. Unlike other buoys that are tethered to the ocean bottom, this floating platform is carried along by ocean currents and makes measurements at regular intervals as it travels.
Data about ocean currents is at present very sparse, noted Dr. Vinayachandran. Satellites cannot detect these currents, and drifting buoys offer a way of making the necessary measurements.
In last year’s trial in the Bay of Bengal, the NIOT could set its buoy to measure sea surface temperature every minute and transmit the average temperature for the previous 15 minutes. The buoy also transmitted its position every hour, worked out using the Global Positioning System (GPS) satellite navigation system. All this data was relayed back to shore over the Insat-3C satellite.
A commercially available drifting buoy, which too was deployed alongside, supplied sea surface temperature and position data only four to five times in a day.
The higher frequency of measurements made by the indigenous buoy showed peaks in sea surface temperature that might otherwise been missed.
With more frequent position data, smaller swirls in the oceans could be detected, according to a paper published by NIOT scientists in Current Science recently.