Doppler Weather Radar (DWR)

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    In News 

    • Recently, the Union Minister of State (Independent Charge) Science & Technology inaugurated the latest upgraded state-of-the-art Doppler Weather Radar (DWR) & Indigenous GPS based Pilot Sonde at Indian Meteorological Office in Jammu.

    Significance of the move

    • The  X-Band Doppler Weather Radar will help in providing real-time monitoring and reporting of weather events affecting the Jammu region.
    • It will be helpful in providing weather forecasts in different sectors including agriculture and tourism forecasts especially for the pilgrims of Mata Vaishno Devi.

    What is Doppler Weather Radar (DWR)?

    • It is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance.
    • 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 equipment to measure rainfall intensity, wind shear and velocity and locate a storm centre and the direction of a tornado or gust front.
    • It provides advanced information, enhancing the lead-time so essential for saving lives and property, in the event of natural disaster associated with severe weather. 
    • Division of  Doppler Radars and their applications: Doppler radar can be divided into several different categories according to the wavelength which are L, S, C, X, K.

     

                                               Image Courtesy:engineeringsadvice.com

    • L Band Radars: Operate on a wavelength of 15-30 cm and a frequency of 1-2 GHz.
      • Mostly used for clear air turbulence studies.
    • S-band radars: They 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. 
      • The drawback to this band of radar is that it requires a large antenna dish and a large motor to power it.
    • C band radars: They operate on a wavelength of 4-8 cm and a frequency of 4-8 GHz. Because of the wavelength and frequency, the dish size does not need to be very large. 
      • This makes C band radars affordable for TV stations. The signal is more easily attenuated, so this type of radar is best used for short-range weather observation.
    • X-band radars: They operate on a wavelength of 2.5-4 cm and a frequency of 8-12 GHz. Because of the smaller wavelength, the X band radar is more sensitive and can detect smaller particles.
      • It is used to detect thunderstorms and lightning.
    • K band radars: They 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 vapour. This band is similar to the X band but is just more sensitive.

    About Doppler effect

    • Doppler Effect refers to the change in wave frequency during the relative motion between a wave source and its observer. 
    • It was discovered by Christian Johann Doppler who described it as the process of increase or decrease of starlight that depends on the relative movement of the star.
    • Doppler Effect works on both light and sound objects

    Radars (Radio Detection and Ranging)

    • It is a device that uses electromagnetic waves in the microwaves region to detect location (range & direction), altitude, intensity and movement of moving and non-moving objects.
    • It has its own source of illumination (a transmitter) for locating targets. 

     

                                                  Image Courtesy: Britannica

    Source: PIB