IMD moots a smaller Doppler radar in cityhttps://indianexpress.com/article/cities/mumbai/imd-moots-a-smaller-doppler-radar-in-city/

IMD moots a smaller Doppler radar in city

If approved,the new radar would be installed at a height of at least 150 metres from sea level.

The Indian Meteorological Department (IMD) has proposed to the state government that it would install a smaller C-band Doppler Weather Radar (DWR) in or around the city as a solution to the issue of height restrictions on buildings within 10 kilometres of the existing radar.

The proposal was discussed by IMD’s deputy director general K S Hosalikar in a meeting with chief secretary J K Banthia on November 1.

“We suggested installing a smaller C-band Doppler radar in or around Mumbai to the chief secretary. It is at a conceptual stage and no final decision has been taken yet,” Hosalikar said.

The IMD had restricted at 70 metres the height of buildings within 10 kilometres of its existing DWR,which is installed atop a 68m high 18-storey building in Colaba,on the ground that tall buildings around the radar could obstruct its beam and thus hamper correct weather forecast.

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If approved,the new radar would be installed at a height of at least 150 metres from sea level,said an IMD official.

“With the new radar,we can get information that we won’t receive if high-rises come up in the vicinity of the existing radar. Data from the ‘shadow’ regions can be taken from the new radar and so we won’t have to limit the height of the buildings near the Colaba radar,” said S G Kamble,director of DWR,IMD.

“We will consider the heights of buildings that are likely to come up in the next 10 years while deciding on the height at which the new radar is installed. It should be installed at least 30-40 kilometres from Mumbai,if not inside it,” he added.

According to the IMD,the main reason behind choosing a C-band radar was that the weight of its antenna,its heaviest component,is five to six tonnes,which is much lighter than the antenna of the existing S-band antenna (15 tonnes) of the DWR at Colaba.

“A lighter radar will be easier to install on an existing building. If a heavier radar is used,like the S-band one,structural support will have to be given to a building from the base level,” said Kamble.

The new C-band radar would have a range of 300 kilometres and cost around Rs 40 crore,IMD officials said. The cost will include site acquisition,civil work on it and procurement of the radar.

Sites at Powai hill,Aarey Colony and Nava Sheva could be some of the options,said another IMD official.

‘No relocation of existing radar’

Meanwhile,Met department officials have advised the chief secretary against the relocation of the its existing Doppler radar. “We have stressed that shifting the radar will be extremely difficult and should be the last option,” Hosalikar said.

“Shifting the 15-tonne Doppler radar means huge risk of damage to it. It was not installed as a single piece,but was assembled at that (68 metres) height. There are high chances that its components such as the transmitters,UPS as well as the antenna may be damaged severely during dismantling and transit to a new location. We feel the radar may not function after shifting,” Kamble said. “Nowhere in India have we relocated a radar before. We always replace an old one,” he added.

Another reason cited against relocation is the possible structural damage to Colaba’s Archana building,where the existing radar is mounted. The 18-storey residential building had undergone structural modifications to accommodate the radar under the supervision of a garrison engineer from the military engineering services. The pillars and beams on the 16 and 17th floors were restrengthened and similar alterations were made to the building,an

official said.

“Shifting the radar will also cause damage to the Colaba building also as there was work done to strengthen the building to hold the 15-tonne radar. The radar occupies almost two floors,” said Hosalikar.

Officials believe installing the radar at other taller buildings in Colaba region would still pose a similar height-restriction issue because the builders will continue to increase the buildings’ height.

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“We had surveyed many sites before installing the existing radar. Meeting the height as well as technical (frequency,non-interference) was a big challenge. There was mounting pressure from the state government,users and we also needed to install the radar to meet our operational requirements. The building at Colaba seemed appropriate at the time as there was a radar mounted on it already,”

Hosalikar added.

Anjali Lukose

anjali.lukose@expressindia.com