Doppler Weather Radar

Context

Extremely severe Cyclone Amphan very likely to move north-northeastwards across northwest Bay of Bengal and cross West Bengal – Bangladesh coasts between Digha (West Bengal) and Hatiya Islands (Bangladesh) close to Sundarbans during Afternoon to Evening hours of 20th May 2020 with maximum sustained wind speed of 155-165 kmph gusting to 185 kmph.

The system is now being continuously tracked by the Doppler Weather Radar (DWR) at Vishakhapatnam (Andhra Pradesh), Paradip (Odisha) and Gopalpur (Odisha).

About Doppler Weather Radar

What is Radar?

Radar (Radio Detection and Ranging) is a device which uses electromagnetic waves in the microwaves region to detect location (range & direction), altitude, intensity and movement of moving and non-moving objects.

What is Doppler Principle?

When the source and the signal are in relative motion to each other there is a change in the frequency observed by the observer. If they are moving closer frequency increases and vice versa.

What is Doppler Radar?

Doppler radar is a specific radar that uses the Doppler principle to produce relative motion data about objects at a distance.

Indian Doppler Radar:

Also known as INDRA series of 2D Radars and developed by DRDO for the use of Airforce and the Army. Some have been even exported to Sri Lanka.

INDRA-1: Is low-level target detection mobile surveillance radar.

INDRA 2: Is a modified version of INDRA radar for ground controlled interception of targets. It uses pulse compression to detect low flying aircraft.

Application of Doppler Radars:

• Aviation,
• Sounding satellites
• Meteorology
• Radar guns
• Radiology and healthcare
• Nursing or clinic purpose
• Bistatic radar (surface-to-air missile)

Doppler Weather Radar (DWR) by ISRO

• For improving weather forecasting services.
• The DWR will help in rainfall estimation and detect thunderstorm, cyclones and other severe weather events within a radius of 400 km.
• DWR has the equipment to measure rainfall intensity, wind shear and velocity and locate a storm centre and the direction of a tornado or gust front.
• Based on Doppler principle the radar is designed to improve precision in long-range weather forecasting and surveillance using a parabolic dish antenna and a foam sandwich spherical radome.

Polarimetric Doppler Weather Radar

• India’sfirst Indigenously developed Polarimetric Doppler Weather Radar (DWR) installed at Cherrapunjee, to Nation on May 27, 2016 remotely from Polo ground in Shillong, Meghalaya.
• The DWR has been designed and developed by Radar Development Area, ISRO Telemetry Tracking and Command Network (ISTRAC), ISRO and manufactured by Bharat Electronics Limited (BEL), Bengaluru.
• The North East, a land of beauty and adventure, has been hit by several natural calamities in the recent past, on account of heavy rain and landslides. This Weather Radar System will enable better weather forecasts, especially for the North Eastern region. This should help in minimising the threat posed by extreme weather conditions
• The polarimetric capability of the Radar will significantly improve the accuracy of rainfall estimation leading to accurate and timely flash flood warnings.
• The DWR, being the first S-band (operating at 2.7 - 2.9 GHz) dual polarimetric Doppler Weather Radar can detect Weather phenomenon upto 500 km.
• This system installed at a place that receives the highest rainfall in Planet Earth, shall open up tremendous research opportunities in the areas of monsoon dynamics, Cloud Physics, impact of orography in precipitation process, precipitation characterisation, thunderstorm and hailstorm genesis and evolution, etc.
• The data from the DWR is also expected to support a host of operational programmers of IMD and NESAC/ISRO. The near real time precipitation estimates from the DWR shall improve the Flood Early Warning System (FLEWS), being developed by NESAC for NE states.
• It will also enable IMD and NESAC to take up operational activities on thunderstorm now-casting and hail now-casting for NE states.