Doppler effect

Why in news?

• The India Meteorological Department (IMD) will install seven new doppler radars in Maharashtra, including Mumbai, this year.

What is Doppler effect?

• The Doppler effect or Doppler shift is the change in frequency of a wave in relation to an observer who is moving relative to the wave source.
• A common example of Doppler shift is the change of pitch heard when a vehicle sounding a horn approaches and recedes from an observer.

About Doppler radars:

• A Doppler radar is a specialized radar that uses the Doppler effect to produce velocity data about objects at a distance.
•  It does this by bouncing a microwave signal off a desired target and analyzing how the object's motion has altered the frequency of the returned signal.
• This variation gives direct and highly accurate measurements of the radial component of a target's velocity relative to the radar.
• 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.
• The radars guide meteorologists, particularly in times of extreme weather events like cyclones and associated heavy rainfall.
• 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.
• India’s east coast, which is frequently affected by the cyclones formed in the Bay of Bengal, has radars operational at eight locations — Kolkata, Paradip, Gopalpur, Vishakhapatnam, Machilipatanam, Sriharikota, Karaikal and Chennai.
• Along the west coast, there are radars at Thiruvananthapuram, Kochi, Goa and Mumbai. Other radars are operating from Srinagar, Patiala, Kufri, Delhi, Mukteshwar, Jaipur, Bhuj, Lucknow, Patna, Mohanbar, Agartala, Sohra, Bhopal, Hyderabad and Nagpur.
• The radars can oversee an area of up to 500 km, with effective range of up to 250 km.
• The modernization and upgrade of existing radars are ongoing and the IMD plans to have a network of 55 doppler radars.

Prelims Question

Consider the following statements regarding Doppler Radar:
1.They are highly useful for weather forecasting.
2.United States and China are the only countries with Doppler radar technology.
Which of the statements given above is/are correct?
(a)1 only
(b)2 only
(c)Both 1 and 2
(d)Neither 1 nor 2

Answer to the Prelims Question