Doppler Weather Radars

Doppler Weather Radars

Subject :Geography

Section : Atmosphere

What is RADAR?

• RADAR is the expansion for Radio, Detection and Ranging.
• Its basic components are a transmitter, receiver, antenna, power supply system, signal processing and high computing devices.
• It works on the principle of electromagnetic waves sent out by the transmitter.
  • The same wave that strikes an object/dense medium is reflected back to the receiver.
  • The distance up to the object is determined based on the speed of the electromagnetic wave, and the time to travel to the object and back.
• There are at least ten types of radars.
• Ground Penetrating Radar:
  • It studies the Earth’s crust up to 9-metre in depth.
  • It is being used by the Defence Geoinformatics Research Establishment (DGRE) at Joshimath.
• InSAR (Interferometric Synthetic Aperture Radar)
  • It makes high-density measurements over large areas by using radar signals from Earth-orbiting satellites and measures changes in land surface.
  • It is also being used in Joshimath and other parts of Uttarakhand.

Doppler radar:

• A Doppler Radar is a specialised radar that uses the Doppler effect to produce velocity data about objects at a distance.
  • When the source and the signal are in relative motion to each other, there is a change in the frequency observed by the observer. This is called the Doppler effect.
  • If they are moving closer, the frequency increases and vice versa.
• A Doppler Weather Radar (DWR) works on the Doppler principle.
  • It is designed to improve precision in long-range weather forecasting and surveillance using a parabolic dish antenna and a foam sandwich spherical radome.
• 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. 

Why DWR is considered superior to other radars?

• Unlike others, a DWR has the ability to detect air motion, wind, speed of wind, rains, temperature, thunderstorms, hail, squalls, lightning, cyclones and cloud movements and volumetric analysis of cloud and reflectivity index, among others.
• It costs approximately ₹10-20 crore per unit.
• The National Ocean and Atmospheric Administration (NOAA) of the US uses 148 of them.
• The Indian Army and Air Force have deployed the Indian Doppler Radar (INDRA) for the detection of aircraft and other objects in the air.

DWR in India:

• Currently India have 37 DWRs.
• Most of them are in plain areas, hilly areas and coastal terrain require more.
• The major advantages of DWRs are, they:
  • cover the entire country
  • give the most precise detection of weather parameters including dynamic weather events turbulence, cyclones, thunderstorms or lightning.
  • alone do the volumetric analysis of clouds that help in the quantification of rain forecasts and cyclonic intensity and precipitation; and
  • precisely detect in real-time normal or routine events
  • Lightening forecast, 3 to 5 days in advance.