Mumbai: Doppler radar to remain defunct for two months, IMD begins testing new radar

The India Meteorological Department’s (IMD) doppler radar in Colaba is likely to remain defunct for at least the next two months, Dr MN Rajeevan, secretary, ministry of earth sciences, told HT on Friday

The India Meteorological Department’s (IMD) doppler radar in Colaba is likely to remain defunct for at least the next two months, Dr MN Rajeevan, secretary, ministry of earth sciences, told HT on Friday.

HT Image

Meanwhile, IMD on Thursday began operating its new C-band radar in Goregaon, only on an experimental basis for the time being. The radar launch, initially planned for December 2020, has been postponed.

A doppler radar provides long-range weather surveillance, detection and forecast for rainfall, cloud formation, thunderstorms and other weather conditions such as tropical storms. There are different types of doppler radars. The one currently installed near the Regional Meteorological Centre in Colaba is an S-band radar which provides surveillance up to 450-500 kilometres. A C-band radar can provide surveillance up to 250-350 km while surveillance by an X-band radar is up to 100 km.

“Our Colaba radar is in a bit of trouble. We have engaged the Bengaluru-based company that assembled it for repairs, but given the current scenario with Covid and the recent lockdown, it is bound to take some time. It is a very specialised work which has been delayed due to unavailability of resources. It might take two to three months before it is running again,” said Dr Rajeevan on Friday.

Independent meteorologists said this was an unfavourable scenario, particularly during monsoon. “Absence of the S-band radar leaves forecasters pretty much in the dark. A satellite image can help in predicting the movement of larger weather features, but for more specific, real-time and local forecasting, radar is essential,” said Akshay Deoras, an independent meteorologist and PhD student at the University of Reading, England.

Experts said that though the C-band radar may likely be commissioned this month, the past performance of IMD’s Colaba radar does not inspire confidence. The Colaba doppler went defunct just before the arrival of Cyclone Tauktae last month. On December 4, 2017, when Cyclone Ockhi brushed past the Mumbai coast, the radar was not functional. The radar was also not functional on multiple days during extreme rainfall events in June and July 2019, and also on June 1, 2020, about 48 hours before Cyclone Nisarga made landfall in Maharashtra.

“Past performance of the S-band radar has been quite sketchy, and one hopes this will not be the case with the new doppler. Also, it’s important to note that a C-band radar suffers from higher signal attenuation than S-band radars and one cannot be a substitute for the other. We need both to work in tandem to get forecasts of real value,” Deoras explained, expressing concern at the prospect of Mumbai not having a single operational radar for the next two months. “Relying mainly on satellite images, as IMD is currently doing, will not be able to accurately predict intense rainfall of the kind that occurred on June 9. This will have direct consequences for the people of the city,” he added.