Military radars were repurposed for meteorological use after WWII, and subsequent upgrades enhanced their precipitation-detecting capabilities. This allows Doppler radars to measure wind speed, making them extraordinarily useful in detecting tornadoes.
Before, meteorologists had to look for visual cues, called a “hook echo,” in order to find tornadoes within storms. Doppler's radar emits pulses of radio waves and listens for any returned signal.
Think about sitting at a light to allow an emergency vehicle to pass, or at a railroad crossing as a train goes by blaring its whistle. This allows meteorologists to differentiate between precipitation types, and even identify ground debris in the air.
The image on the right is called correlation coefficient, and the small circular blue area indicates an area of clear air encircled by objects detected in the air (the green color) and similarly shaped raindrops (shown in red). This is called a “debris ball,” and it's a telltale sign on a dual-pol radar of a tornado on the ground.
However, phased array radar is expected to cost billions of dollars to implement, and with dual-polarization recently launched, it's unlikely to occur until well into the next decade. I've had a lifelong interest in the weather spanning more than 30 years, culminating with the pursuit of a Meteorology degree from Minersville University in Pennsylvania.
You might have seen my work on Digital Trends, PC World, VentureBeat, or even the New York Times website. At Weather Station Advisor, I joined the team to provide you with the best reviews, recommendations and advice to get the most out of your investment.
As I've found out on my own, weather stations aren't cheap, and it's easy to make a costly mistake. Many of us are familiar with the traditional ways of gathering weather data but don't realize the importance of using radar technology in meteorology.
Radar technology has been around for some time, with its origins dating back as far as 1886, when scientist Heinrich Hertz illustrated that radio signals could be reflected off objects. The aim is to explain and illustrate precisely what a weather radar is, its characteristics and the way in which it is used for all meteorological purposes.
A weather radar is an observational piece of equipment for detecting and picturing different forms of precipitation like rain, hail, and snow. It does so by sending out electromagnetic or microwaves and then receiving & analyzing the signals that are reflected back (also called echoes).
You now have a pretty good idea what a weather radar looks like, as the accompanying picture clearly shows. Weather radars come in different sphere sizes and tower heights, depending on their specific purpose, the type of technology used, and the topography of the surrounding terrain.
While rotating, the dish sends out radio (electromagnetic/microwave) waves up to a maximum distance of around 230 km (143 miles). The length of time it takes the echo to return to the sender indicates how far away the precipitation is from the radar.
The strength of the echo, on the other hand, provides a strong suggestion of the type of precipitation encountered (rain, hail, or snow). Although a radar image does not give you a clear and definite forecast, it shows you where the rainfall has been, as well the direction in which it may be moving.
This helps anyone to view the picture to know when the image was created, no matter where in the world or in which timezone they are. The radar beam travels in a straight line, meaning beyond its maximum range, it is unable to detect objects close to the surface of the ground.
As a result of the previous point, the radar may be able to pick up precipitation that is much higher up in the air beyond its optical limit. Sometimes a radar can “falsely” pick up what is perceived to be precipitation, which is in reality flocks of birds, smoke, or swarms of insects.
Radar beams cannot “see'' through and are obstructed by permanent fixtures such as tall buildings and mountains. This is one of the main reasons why weather radars are located in large open areas.
An object moving towards the radar compresses the returning frequency, causing a higher pitch. An object moving away from the radar “stretches” the returning frequency, creating a lower pitch.
In short, a higher frequency means an object (for example, rain) is moving towards the radar. This ability is a very important function of modern weather radars implementing the Doppler effect.
It allows meteorologists to determine the direction a weather system is moving in with a much greater degree of certainty. It is clear to see how important the addition of weather radar systems is to the field of meteorology.
Video Working together, engineers, technicians, and scientists collectively design, develop and operate the advanced technology of radars that are used to study the atmosphere.
Doppler weather radars are remote sensing instruments and are capable of detecting particle type (rain, snow, hail, insects, etc), intensity, and motion. Radars emit microwave energy, a longer wavelength, highlighted in yellow.
Part of this beam of energy bounces back and is measured by the radar, providing information about the object. Radar can measure precipitation size, quantity, speed and direction of movement, within about 100-mile radius of its location.
Radar can be used to help study severe weather events such tornadoes and hurricanes, or long-term climate processes in the atmosphere. Continuously modified and improved, this state-of-the-art radar system now includes dual-wavelength capability.
Polka’s mission is to promote a better understanding of weather and its causes and thereby ultimately provide improved forecasting of severe storms, tornadoes, floods, hail, damaging winds, aircraft icing conditions, and heavy snow. The Near Diaper Cloud Radar (Her) can be mounted to the underside of the wing of the NSF/Near Diaper research aircraft (a modified Gulf stream V jet) and delivers high quality observations of winds, precipitation and other particles.
It was designed and manufactured by a collaborative team of mechanical, electrical, aerospace, and software engineers; research scientists; and instrument makers from EOL. This accidental discovery revolutionized the way we look at the weather and it has helped save countless lives over the past six decades.
Its uses range from watching light rain slowly lumber toward you to tracking the precise location of a tornado tearing through towns hundreds of miles away. HOW IT WORKS Troops on the front lines during World War II discovered that the radar they used to track incoming enemy aircraft also detected precipitation, giving them the ability to keep watch over both storms and airplanes.
The resulting data is displayed on a map using a rainbow scale that typically spans from light blue to dark red and purple, with cooler colors indicating lighter precipitation and warmer colors showing heavy precipitation. Solid batches of oranges, reds, and purples on a radar image usually indicate an intense thunderstorm.
This dual radar beam allows us to see the size and shape of the objects falling through the atmosphere. This is important as it can tell us the difference between rain, hail, snow, sleet, and foreign objects like tornado debris.
When the red and green colors are very close together within a thunderstorm, this is called a rotational couplet, and this is where a tornado is most likely happening. The couplet in the right panel of the radar image above shows the winds swirling around the intense EF-4 tornado that struck Tuscaloosa and Birmingham, Alabama, on April 27, 2011.
This serves as an incredible advance notice to confirm tornadoes when it would have been otherwise impossible because of heavy rain or lack of sunlight. Radar can also spot plumes of smoke from wildfires, swarms of insects, flocks of birds, frontal boundaries (like cold fronts and sea breezes), and even tragedies like the disintegration of the Space Shuttle Columbia over Texas in 2003.
The basics of radars is that a beam of energy, called radio waves, is emitted from an antenna. The larger the object, the greater the amount of energy that is returned to the radar.
In addition, the time it takes for the beam of energy to be transmitted and returned to the radar also provides is with the distance to that object. By their design, Doppler radar systems can provide information regarding the movement of targets as well as their position.
By measuring the shift (or change) in phase between a transmitted pulse and a received echo, the target's movement directly toward or away from the radar is calculated. As an object moves away from your location, sound waves are stretched resulting in a lower frequency.
Doppler's radar pulses have an average transmitted power of about 450,000 watts. By comparison, a typical home microwave oven will generate about 1,000 watts of energy.
In precipitation mode, the radar completes a volume scan every 4-6 minutes depending upon which volume coverage pattern (VCP) is in operation, providing a 3-dimensional look at the atmosphere around the radar site. The “dual-pol” upgrade included new software and a hardware attachment to the radar dish that provides a much more informative two-dimensional picture.