Highrises in Mumbai need Met nod

MUMBAI: Developers building skyscrapers over 70 metres high (20 floors) in the island city now face another hurdle to get their plans approved. In perhaps a first in the city, the regional meteorological centre has lopped off the height of two proposed towers by half because they could have interfered with the new Doppler weather radar installed on top of the 18-storey Archana building in Navy Nagar three years ago.

There is no provision in the development control rules that invest the weather department with such powers. But the BMC's high rise panel insists that builders procure a no-objection certificate from the Met department if the proposal falls within a 10-km radius of the radar.

The department had initially pushed for a radius of 25km.

Municipal commissioner S J Kunte said the state government had formed a committee under the chief secretary to iron out this issue, but no decision had been taken so far. But city builders and architects are crying foul, saying in most global cities such weather monitoring systems are installed a couple of hundred kilometres away.

Information procured under the Right to Information Act shows that early this month, the department reduced the height of a proposed Wadala skyscraper from 143 meters (40 floors) to 84.87 meters (24 floors). "The proposed building with a height of 143m will obstruct the radar beam during radar operations,'' the department informed the architect of the building planned at Dosti Complex, Wadala.

Last year, the IMD had reduced the height of an upcoming skyscraper in Girgaum from 172.5m (50 floors) to 73.56m (21 floors). The developer, Orbit Corporation, said it was just an interim clearance and it would challenge the decision.

The deluge which devastated Mumbai in July 2005 forced the authorities to replace the conventional cyclone detection radar with the sophisticated Doppler weather radar. The IMD said its officials had visited many sites, but due to high rise buildings failed to select a proper location. "These buildings obstruct the radar signal beam from detecting clouds and other weather phenomena,'' it said. A site in Aarey Milk Colony, Goregaon (east), was rejected due to high steel towers nearby and no development restrictions. Finally, the Indian Navy permitted the department to set up the radar on a Navy Nagar building.

"The radar project was held up for four to five years because the IMD could not find a suitable site in Mumbai. Now, if construction of new high rise buildings is permitted in south and central Mumbai, the radar operational services will be blocked over a large area,'' R V Sharma, deputy director general of meteorology, has written to the state government.

Doppler radar and its function

The Doppler radar provides additional data related to wind speed and droplet formation by assessing cloud movement and fires images every 10-15 minutes.

A Doppler radar produces velocity data about objects at a distance by beaming a microwave signal towards a desired target and listening for its reflection. It then analyses how the frequency of the returned signal has been altered by the object's motion.

In recent past

After the 26/7 deluge, the need for a Doppler radar was felt in the city to predict heavy spells of rainfall. After a long delay, a China-made radar was brought to the city in 2009.

It was kept unused for six months, after which it was sent back to Delhi as the navy objected to Chinese experts entering the area to install it. After this setback, it was decided to use an indigenously made Doppler. After a delay of five years, an S-band Doppler radar was installed in October, 2010. The IMD tested the radar all throughout 2011 and continued to have some technical problems in operating the radar to its optimum in 2012. This year, almost three years after it was installed, the S-Band Doppler Radar has been giving the city almost impeccable weather forecasts.