Updated: May 17, 2021 10:06:28 pm
Even as Cyclone Taukate brushed past the Mumbai coast and resulted in strong winds and torrential rain, the India Meteorological Department’s (IMD) lone Doppler radar in the city — which surveys weather patterns, and forecasts — was out of commission since it stopped working from Sunday evening.
This is the third time since 2017 that the Doppler radar has been non-functional when a cyclone has brushed past the Mumbai coast.
An IMD official said, “The Doppler radar is not working owing to technical problems. Engineers are looking into it.” However, the official did not know when the radar would be functional.
The radar, installed in 2010 at the Regional Meteorological Centre in Colaba in South Mumbai, can carry out weather surveillance up to 450-500 km radius from its location. Doppler radar is crucial for gauging the intensity of rainfall and impact area in the city in real time.
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Surface rainfall intensity (SRI), a feature of the radar, helps to measure the speed of approaching clouds, height, the time in which the clouds will bring rain to the city, the amount of rainfall the approaching clouds hold and predict the precipitation accumulation, which will help the BMC issue specific warnings about areas that may flood.
A Doppler radar is also efficient in tracking clouds that cause thunderstorms. Real-time forecasting helps give accurate information on areas where it may rain heavily.
In its absence, satellite pictures and wind profile are used by IMD to give a forecast.
“A Doppler radar not working will not have an impact on the forecast of the cyclone path, and weather models working on it. However, to forecast the impact of that cyclone on a big city like Mumbai, a Doppler radar is more effective. We need Doppler radar for real-time monitoring and the impact of such weather systems,” said Akshay Deoras, independent meteorologist and PhD researcher at the department of meteorology, University of Reading, UK.
The idea to install a Doppler radar was mooted after the city received 994 mm of rainfall on July 26, 2005, leading to large-scale death and devastation.
The radar, which cost Rs 10 crore, was installed in October 2010, but owing to technical glitches it was not functional till 2012.
The Doppler radar was down a day before Severe Cyclonic Storm ‘Nisarga’ brushed past Mumbai on June 2 last year. During June and July 2019, when the city witnessed extremely heavy rain, the Doppler radar was dysfunctional on both days due to technical difficulties. It was also shut on December 4, 2017, when Cyclone Ockhi brushed past the Mumbai coast.
IMD is expecting to install a C-Band radar, which has surveillance up to 250-350 km, at Dindoshi in Goregaon, by the end of this year. IMD has also planned four X-Band radars, which have a surveillance radius of 100 km, to be strategically set up in different locations in the city to have spatial coverage of hyperlocal weather changes. The X band radars can better detect convective clouds and thunderclouds, which brought rain in July 2005.
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