New method to track cyclone paths unveiled
[NEW DELHI] A prediction method developed by NASA scientists holds promise for filling in information gaps and improving advance warning in cyclone-prone areas.
Prompted by the devastating cyclone Nargis that struck the Myanmar coast in May 2008, killing an estimated 135,000 people, NASA scientists re-examined their data and modelling approaches using Nargis as a test case.
In the case of Nargis, forecasters tracking the cyclone in late April 2008 predicted it would hit Bangladesh but to their surprise it veered east — gaining strength along the way — and struck Myanmar on 2 May.
The NASA scientists retraced the cyclone's path using new three-dimensional satellite images and atmospheric data from the Atmospheric Infrared Sounder (AIRS) instrument on NASA's Aqua satellite. They published their research in Geophysical Research Letters last month (27 March).
AIRS is the most advanced atmospheric sounder — a 'weather balloon' equipped with instruments to measure wind speed, direction, temperature, pressure and moisture content — and can improve a forecast by more accurately locating a cyclone's centre, says Oreste Reale, associate research scientist at the Laboratory for Atmospheres, in the NASA Goddard Space Flight Center.
Most weather forecasting models use AIRS data extracted only from clear-sky regions, as it is difficult to extract satellite data from cloudy areas, he told SciDev.Net.
"It is now possible to use high-quality AIRS data also from cloudy regions. This improves pinpointing a cyclone's position, and assesses their structure earlier," he says.
All AIRS data is freely available and the additional 'cloudy-skies' data can now be integrated with other data sets from earth-observing satellites, ocean buoys, aircraft and land-based sensors that are used to forecast cyclones.
Reale says their new method will be useful for cyclone forecasting in the northern Indian Ocean, even in the Bay of Bengal.
Cyclone paths are difficult to predict in the Bay of Bengal because its small dimensions and shallow, 'funnel' shape cause water to churn up faster and higher, making the cyclone of shorter duration. This gives scientists less time to track them.
Reale says that with the additional data, scientists can "make a forecast for a Nargis arrival on Myanmar up to four days in advance. Without this procedure, we would make a forecast for Nargis landfall just one or two days in advance".
Shishir Dube, professor at the Centre for Atmospheric Sciences at the Indian Institute of Technology — which is working on cyclone forecasts — says that the new method is worth trying for the Indian region.