Context: The Union Ministry of Earth Sciences has approved an X-band radar to be installed in Kerala's Wayanad district, which was hit by devastating floods and landslides killing more than 200 people in July 2024.
How do radars work?
- Radar is short for ‘radio detection and ranging’. The device uses radio waves to determine the distance, velocity, and physical characteristics of objects around the device. A transmitter emits a signal aimed at an object whose characteristics are to be ascertained (in meteorology, this could be a cloud). A part of the emitted signal is echoed by the object back to the device, where a receiver tracks and analyses it.
- One of the important kinds of radars is Weather radar or a Doppler radar.
- The Doppler effect is the change in frequency of sound waves as their source moves towards and away from a listener.
- In meteorology, Doppler radars can reveal how fast a cloud is moving and in which direction based on how the cloud’s relative motion changes the frequency of the radiation striking it.
- Modern Doppler radars can monitor weather conditions and anticipate new wind patterns, the formation of storms, etc.
What is an X-band radar?
- Doppler radar relies on Rayleigh scattering, when the scatterer is much smaller than the wavelength of the radiation. A radar trying to ‘see’ smaller particles like rain droplets or fog will need to use radiation of lower wavelengths, like in the X-band.
- An X-band radar is radar that emits radiation in the X-band of the electromagnetic spectrum: 8-12 GHz, corresponding to wavelengths of around 2-4 cm (this is in the microwave part of the spectrum.)
- Due to operating at a smaller wavelength, X-band radars are more sensitive and can detect smaller particles compared to other radar bands. The smaller wavelengths allow the radar to produce images of higher resolution.
- However, the greater the frequency of any radiation, the faster it will be attenuated. So, X-band radars have a relatively shorter range.
- X-band radars are typically used for studies about cloud development and light precipitation due to their abilities to detect tiny water particles and snow.
- Significance: In Wayanad, the new radar is expected to be able to monitor the movements of particles, such as soil, to inform landslide warnings. The device will also perform high temporal sampling, i.e., rapidly sample its environs, allowing it to spot particle movements happening in shorter spans of time.
S-band radars vs. X-band radars:
There are two types of radars that are frequently used: S-band and X-band.
1. S-band radar:
- Operating frequency: 2-4 GHz.
- Speciality: Long-range detection.
- Benefits: Capable of operating accurately even in severe weather conditions (heavy precipitation and cloud cover), making it useful for civilian and military aircraft navigation.
- Applications:
- Used for maritime surveillance as it provides long-range coverage. E.g., Used by naval warships for precise tracking of threats, both aerial and surface, at greater distances.
- Used in weather forecasting due to their ability to operate in adverse weather.
2. X-band Radar:
- Operating frequency: 8-12 GHz.
- Speciality:
- Higher-resolution short-range imaging for target identification.
- Detection of smaller objects because X-band radars (operating on smaller wavelengths) have high sensitivity.
- Benefits: They have compact size and thus can be installed on mobile platforms.
- Limitations:
- More susceptible to be impacted by weather conditions due to their smaller wavelengths. (atmospheric conditions like rain can reduce their range)
- Have relatively shorter range than S-radars.
- Applications:
- Used in short-range weather forecasting and for monitoring localised weather phenomenon, like, heavy rainfall, thunderstorms, weather patterns, cyclones etc.
- X-band technology is also used for civil, military, and government settings for tasks such as:
- Weather Monitoring (localised weather phenomenon)
- Air Traffic Control (high resolution imaging helps in the identification/distinguishing and tracking of aircrafts)
- Maritime Vessel Traffic Control
- Vehicle Speed Detection for Law Enforcement
- Missile guidance systems (can track small, fast-moving targets with precision).
How many radars does India have?
- The India Meteorological Department (IMD) started using radar for weather applications in the early 1950s. The first indigenously designed and manufactured X-band storm detection radar was installed in 1970 in New Delhi. In 1996, IMD replaced 10 outdated X-band radars with digital X-band radars. In its X-band radar network, India has both wind-finding and storm-detecting radars, and some with dual capabilities.
- The country also uses S-band radars (2-4 GHz) for long-range detection. The first S-band cyclone detection radar was installed in Visakhapatnam in 1970 and the first locally made variant was commissioned in Mumbai in 1980.
- In September 2024, the Ministry of Earth Sciences said India is set to have 56 additional Doppler radars in a few years. On September 11, the Union Cabinet cleared the ₹2,000-crore ‘Mission Mausam’ to upgrade meteorological infrastructure in the country. This includes installing up to 60 meteorological radars until 2026 under the Mission’s first phase.
- The government has started the process to procure and install 10 X-band Doppler radars to improve weather forecasting in the northeast States and in Himachal Pradesh’s Lahaul and Spiti district.