A new doppler radar to boost the weather forecasting system in the cyclone prone eastern coast will be commissioned in Gopalpur in Odisha next month. It will be the sixth such radar on the country’s east coast. The others are located in Chennai, Kolkata, Machilipatnam, Visakhapatnam and Paradip. The move to set up additional radar assumes significance as the eastern coast is prone to cyclones and better forecast will help authorities in taking timely action. Kochi, Bhuj, Mumbai and Karaikal on the western coast have doppler radars, while the equipment is being set up in Goa

Doppler radar is an observational tool for monitoring and predicting severe weather events such as thunder storms, hailstorms, cyclones and tornados within a radius of 300 km. It not only gives information about precipitation but also about wind velocity.

CROSS REFERENCES

A special type of Radar, called Doppler radar , uses the Doppler effect to ascertain wind velocity in heavy thundershowers, tornadoes, and hurricanes; a type of radar that uses the Doppler shift to measure the speed and direction of a target, as a moving object, storm, or tornado. Doppler radar is defined as a tracking system that uses the Doppler effect to determine the change in the frequency, movement and location of sounds, objects, waves of light, storms and other weather elements.

In a rotating storm such as a hurricane or tornado, the maximum sustained wind speed can be found by measuring the difference in frequency of echoes returned from approaching rain droplets and receding rain droplets. A more primitive form of Doppler radar is used by law enforcement personnel to enforce traffic speed limits.
weatherman uses Doppler radar at a local TV news station to forecast storms.

a policeman use Doppler radar to evaluate the speed of an oncoming vehicle.

an astronomer would use Doppler radar to measure the speed of a moving star.

There are many everyday examples of the Doppler effect –

the changing pitch of police and ambulance sirens, or train whistles and racing car engines as they pass by.

In every case, there is an audible change in pitch as the source approaches and then passes an observer.

The frequency and wavelength of an electromagnetic field are affected by relative motion. This is known as the Doppler effect . Only the radial (approaching or receding) component of motion produces this phenomenon. The Doppler effect also occurs with acoustic waves. The Doppler effect is observed whenever the source of waves is moving with respect to an observer. The Doppler effect can be described as the effect produced by a moving source of waves in which there is an apparent upward shift in frequency for observers towards whom the source is approaching and an apparent downward shift in frequency for observers from whom the source is receding.

The Doppler effect can be observed for any type of wave – water wave, sound wave, light wave, etc. We are most familiar with the Doppler effect because of our experiences with sound waves. Perhaps you recall an instance in which a police car or emergency vehicle was traveling towards you on the highway. As the car approached with its siren blasting, the pitch of the siren sound (a measure of the siren’s frequency) was high; and then suddenly after the car passed by, the pitch of the siren sound was low. That was the Doppler effect – an apparent shift in frequency for a sound wave produced by a moving source. This effect is called the ‘Doppler effect’ after Christian Andreas Doppler, an Austrian mathematician who discovered that the frequency of sound waves changes if the source of sound and the observer are moving relative to each other.

The Doppler effect is significant in low-earth-orbit (LEO) satellite systems. All LEO satellites are constantly moving relative to each other and to points on the surface. This causes variations in the frequencies and wavelengths of received signals. In geostationary satellite systems, Doppler effect is not a factor unless the end user is on board a spacecraft or high-speed aircraft.

If the source of an EM field is approaching an observer, the frequency increases and the wavelength decreases. If the source is receding, the frequency decreases and the wavelength increases.
Electromagnetic Radiation:

                              Energy radiated in the form of a wave as a result of the motion of electric charges. A moving charge gives rise to a magnetic field, and if the motion is changing (accelerated), then the magnetic field varies and in turn produces an electric field. These interacting electric and magnetic fields are at right angles to one another and also to the direction of propagation of the energy. Thus, an electromagnetic wave is a transverse wave.

The theory of electromagnetic radiation was developed by James Clerk Maxwell and published in 1865. He showed that the speed of propagation of electromagnetic radiation should be identical with that of light, about 186,000 mi (300,000 km) per sec. Subsequent experiments by Heinrich Hertz verified Maxwell’s prediction through the discovery of radio waves, also known as hertzian waves.

Light is a type of electromagnetic radiation, occupying only a small portion of the possible spectrum of this energy. The various types of electromagnetic radiation differ only in wavelength and frequency; they are alike in all other respects. In order of decreasing wavelength and increasing frequency, various types of electromagnetic radiation include: electric waves, radio waves (including AM, FM, TV, and shortwaves), microwaves, infrared radiation, visible light, ultraviolet radiation, X rays, and gamma radiation.

The number of cycles per unit of time is called the frequency. Frequency is the number of occurrences of a repeating event per unit time.

The wavelength is the distance in space required to complete a full cycle of a frequency.The distance between one peak of a wave to the next corresponding peak, or between any two adjacentcorresponding points, defined as the speed of a wave divided by its frequency.

The wavelength of a sound is the inverse of its frequency. lower frequencies have longer wavelengths. We are able to hear lower frequencies around a corner because the longer wavelengths refractor bend more easily around objects than do shorter ones.

The word Cyclone is derived from the Greek word Cyclos meaning the coils of a snake. It was coined by Henry Peddington because the tropical storms in the Bay of Bengal and the Arabian Sea appear like coiled serpents of the sea. Cyclones are caused by atmospheric disturbances around a low-pressure area distinguished by swift and often destructive air circulation. Cyclones are usually accompanied by violent storms and bad weather. The air circulates inward in an anticlockwise direction in the Northern hemisphere and clockwise in the Southern hemisphere.

Cyclones are given many names in different regions of the world – They are known as typhoons in the China Sea and Pacific Ocean; hurricanes in the West Indian islands in the Caribbean Sea and Atlantic Ocean; tornados in the Guinea lands of West Africa and southern USA.; willy-willies in north-western Australia and tropical cyclones in the Indian Ocean.