New Doppler Units, to strengthen radar network:IMD

• India Meteorological Department (IMD) announced that it will install seven new doppler radars in Maharashtra, in 2021.
• With the radar observations, updated every 10 minutes, forecasters can follow the development of weather systems as well as their varying intensities, and accordingly predict weather events and their impact.

• Doppler radars of varying frequencies — S-band, C-band and X-band — are commonly used by the IMD to detect and track the movement of weather systems, cloud bands and gauge rainfall over its coverage area of about 500 km.

Significance:

• The radars guide meteorologists, particularly in times of extreme weather events like cyclones and associated heavy rainfall and can predict weather events and their impact.

• In January 2021, the Union Minister for Earth Sciences commissioned two of the ten indigenously built X-Band Doppler Weather Radars (DWR) to closely monitor the weather changes over the Himalayas.

Radar (Radio Detection and Ranging):

• It 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.

Doppler Radar:

• It is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance.

• Doppler effect: 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.

• Doppler Weather Radar (DWR): 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.

• 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.

• Types Of Doppler Radars :

• Doppler radar can be divided into several different categories according to the wavelength which are L,S,C,X,K.

• X-band radar:

• It operates 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.
• Four X-band and one C-band radar will be deployed over Mumbai in 2021.

• C-band radars:
• It operates 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.
• The signal is more easily attenuated, so this type of radar is best used for short range weather observation.
• It guides at the time of cyclone tracking.

• S band radars:
• It operates 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.