RF Wireless World

Weather radar system

It is a technology used to detect and monitor precipitation. It can also be used to study and predict weather patterns and phenomena. It is used to determine climatic conditions such as wind speed, cloud formations, sea water tides and so on by meteorologists and weather forecasters.

Similar to the other radars, this type of radar also transmits radio frequency waves or microwave. It determines various parameters based on received scattered pulse wave. Targets here can be trees, clouds, raindrops, snowflakes, bumblebees, hailstones and so on. Many modern weather radars use doppler effect to measure motion (i.e. speed and direction) of the precipitation particles. It is this radar which helps pilot fly the aircraft in the thick dark cloud and poor visibility conditions. The weather radar system usually transmits radio wave of about 3000MHz frequency (About 10cm wavelength). It transmits short pulses at this frequency at the rate of 1000 pulses per second.

Weather radar working principle

Let us understand weather radar diagram, its components and working principle. It consists of transmitter, receiver, antenna system, feedhorn and radome.
•  Transmitter consists of RF signal generation modules viz. modulator, RF upconverter and power amplifier.
•  Receiver consists of RF signal analysis modules viz. LNA, RF downconverter, demodulator and display.
•  Antenna is used to transmit the signal into the air and capture the RF signal from the air.
•  Feedhorn focus the received signal into the receiver part and also directs the signal from the transmitter part to the antenna for transmission in the air.
•  Radome is used to protect antenna and other subsystems from high speed winds.
•  Data processing is carried out on the received signals to create series of images called radar echoes or reflectivity maps.
•  Meteorologists analyze the radar data to interpret various weather phenomena such as rain, hail, snow and other severe conditions such as thunderstorms and tornadoes.

Weather radar scanning techniques

The scanning techniques allow meteorologists and research teams to observe different aspects of the atmosphere such as precipitation intensity, movement and structure.

For meteorology application radar uses scanning techniques such as PPI and RHI.
➨Plan Position Indicator (PPI): In this type, radar keeps elevation angle fixed and varies azimuth angle. If radar rotates about 360 degree, it is referred as surveillance scan. If it rotates less than 360 degree, it is referred as sector scan.
➨Range Height Indicator (RHI) : In this type, radar keeps its azimuth fixed and varies elevation. It is rotated towards the sky. Data for different elevation angles are collected for some time and later will be analyzed.
➨Volume Scan : In this scan technique, weather radar system combines multiple PPI and RHI scans at different elevation angles to create 3D view of the atmosphere.
➨Surveillance scan : It involves regular PPI scans at different elevation angles to track movement and intensity of precipitation across wide area.
➨Doppler scan : Doppler radar measures velocity of precipitation particles by analyzing frequency shift of radar waves reflected off moving objects.
➨Dual polarization scan : The radar emits both horizontal and vertical polarized waves. It helps meteorologists in determining particle shape, size and type.
➨Sector scan : Instead of scanning full 360 degree, the radar focuses on specific sector.
➨Adaptive Scan : It can adapt scanning strategies based on evolving weather conditions.

Benefits of weather radar

Following are the advantages or benefits of weather radar system.
➨It can accurately detect presence and intensity of various types of precipitation.
➨It is instrumental in identifying and tracking severe weather phenomena.
➨It provides real time information about movement and evolution of storms.
➨It can estimate amount of rainfall occurring in specific area or region.
➨It plays significant role to observe and model water cycle of the Earth.
➨It provides useful information about wind shear, turbulence and other weather conditions. This is useful at airports for aircraft during takeoff, landing and during flight operations.
➨It aids in emergency management and in coordinating disaster response efforts.
➨It helps communities to stay informed about changing weather conditions and potential hazards.

Conclusion : Overall, weather radar systems is very useful in monitoring, understanding and predicting weather patterns and severe weather events. It helps meteorologists, emergency responders and general public to make timely actions or decisions as per real time weather conditions.

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