India now has 47 Doppler Weather Radars covering 87% of the country’s area, aiding in real-time tracking of extreme weather events like cyclones, heavy rainfall, and snowfall. 

About Doppler Radars

• Doppler radars are radar systems that use the Doppler effect to measure the speed and direction of moving objects like rain droplets and wind.
• They transmit radio waves and analyse the frequency shift in the reflected signal to detect motion.

How Doppler Weather Radars Work?

• Transmission of radio waves: The radar emits short pulses of microwave radio waves into the atmosphere.
• Scattering by precipitation: Raindrops, snow, or hail reflect part of the signal back to the radar as echoes.
• Doppler effect: If these targets are moving, the frequency of the returned signal changes (higher if moving toward, lower if moving away).
• Velocity calculation: The radar measures this frequency shift to determine wind speed and direction within storms.
• Distance & intensity: Time delay of the echo gives distance, while signal strength indicates rainfall intensity.
• Data display: Information is processed into colour-coded maps showing precipitation and storm movement.

Advantages of Doppler Radar

• Unlike conventional radars, DWRs can also detect movement of weather targets.
• They track the phase shift (change in wave pattern) between transmitted and received signals.
• This allows calculation of speed and direction of rain or storm movement—toward or away from the radar.

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Types of Doppler Radars Used in India

• In India, DWR of varying frequencies — S-band, C-band and X-band — are commonly used by the IMD to track the movement of weather systems and cloud bands, and gauge rainfall
• They normally have a coverage area of about 500 km.
• Band Coverage & Use Case: 
• • S-band Long-range weather monitoring
  • C-band Cyclone tracking and rainfall measurement
  • X-band Detects thunderstorms, lightning, and local storms

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