DOPPLER WEATHER RADAR

DOPPLER WEATHER RADAR

WHAT IS A RADAR ?

• RADAR stands for Radio, Detection and Ranging.
• Its basic components are a transmitter, receiver, antenna, power supply system, signal processing and high computing devices.

WORKING OF RADAR

• 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.

TYPES OF RADAR

• There are at least ten types of radars.
• GROUND PENETRATING RADAR : The Ground Penetrating Radar studies the Earth’s crust up to 9­metre in depth and is being used by the Defence Geoinformatics Research Establishment (DGRE) at Joshimath.
• INFEROMETRIC SYNTHNETIC APERTURE RADAR (InSAR) : The InSAR that makes high ­density measurements over large areas by using radar signals from Earth­ orbiting satellites and measures changes in land-surface 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.

DOPPLER WEATHER RADAR (DWR)

• It is designed to improve precision in long ­range weather forecasting and surveillance using a parabolic dish antenna and a foam sandwich spherical radome.
• It has the 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.
• 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.

TYPES OF DOPPLER RADARS

Doppler radar can be divided into different categories depending upon the wavelength such as L, S, C, X, K.

• L band radars operate on a wavelength of 15-30 cm and a frequency of 1-2 GHz. L band radars are mostly used for clear air turbulence studies.
• X band radars: These radars operate on a wavelength of 2.5-4 cm and a frequency of 8-12 GHz. Due to the smaller wavelength, the X band radar is more sensitive and can detect smaller particles.
• K band radars operate on a wavelength of .75-1.2 cm or 1.7-2.5 cm and a corresponding frequency of 27-40 GHz and 12-18 GHz. This band is split down the middle due to a strong absorption line in water vapor. This band is similar to the X band but is just more sensitive. This band also shares space with police radars.
• S band radars operate on a wavelength of 8-15 cm and a frequency of 2-4 GHz. Because of the wavelength and frequency, S band radars are not easily attenuated. This makes them useful for near and far range weather observation.

APPLICATIONS :

• X-band radars can become less effective easily, hence they are used for only very short-range weather observations.
• They are also used for studies on cloud development and other related technologies because they can detect the tiny water particles and also used to detect light precipitation such as snow.

ADVANTAGES OF DWR

• The major advantages of DWRs are they cover the entire country.
• They give the most precise detection of weather parameters including dynamic weather events turbulence, cyclones, thunderstorms or lightning.
• They alone do volumetric analysis of clouds that help in the quantification of rain forecasts and cyclonic intensity and precipitation.
• DWR precisely detect in real ­time normal or routine events.

ARE DOPPLER WEATHER RADAR POPULAR GLOBALLY?

• DWRs are one of the most popular radars.
• The National Ocean and Atmospheric Administration (NOAA) of the US uses 148 of them, which speaks volumes about their efficacy.
• The Indian Army and Air Force have deployed the Indian Doppler Radar (INDRA) for the detection of aircraft and other objects in the air.

INDIA & DOPPLER WEATHER RADAR

• As on January 15, 2023, the country has 37 DWRs.
• The Ministry of Earth Sciences is also preparing to cover the entire Country the Doppler weather radar network by 2025 for more accurate forecasts related to extreme weather events.
• These are mainly spread across the plains. But mountainous and coastal terrain requires more radars, which are being procured.
• By 2024­25, India is expected to have 25 more DWRs taking the total number to 62 radars. That would improve forecast precision.

Syllabus : MAINS GS3-SCIENCE & TECHNOLOGY, SPACE SECTOR