What role does Doppler radar play in improving weather forecasting ability?

During World War II, radar was first used in the military field. They tried to find the enemy plane by the reflection of the radio beam, but their plan was affected by the chaotic reflection caused by the rain. Scientists are very excited to see this chaotic situation. Because they found an instrument that can detect the substances hidden behind the clouds. A few years later, radar became the standard tool for studying storms. Scientists even used radar to discover the relationship between the air circulation above the clouds and the rotation of tornadoes on the ground.

Traditional radar has its limitations. When the storm moves, the reflected wave (microwave echo) of the radar observer will also move, but most of the movement inside the storm will disappear because of the huge white water droplets. But in the 1950s, researchers developed a new type of radar called Doppler radar. It can detect the movement inside the clouds. Now, Doppler radar plays an important role in improving weather forecasting ability, and can predict the development of short-term strong storms.

Radar releases microwaves, which are reflected by substances in the air. When Doppler radar reflects microwave, we can clearly observe the slight change of wave frequency. If a drop of rain hits the radar, the frequency of reflected waves will increase; On the contrary, the farther the water drops are from the radar, the lower the wave frequency will be. This law of wave frequency was discovered by Australian physicist Doppler in 1842. He explained why the whistle sounded so loud when the train approached, and the sound faded when the train left. At first, Doppler radar was very heavy. Computers can't undertake data operations. In the 1970s, tornado researchers used Doppler radar to detect several storms. In the early 1980s, scientists used the Doppler radar group to show the three-dimensional structure of storms and explain the existence of micro-explosions that threatened airplanes.

Doppler radar can also help weather forecasters measure rainfall. The latest radar can also accurately predict floods. Through polarized Doppler radar, researchers can distinguish vertical and horizontal reflected waves one by one. Eliminating strong light stimulation is the same as polarizing sunglasses. Meteorologists determine the size of raindrops according to the comparison between vertical waves and horizontal waves: the proportion of vertical waves and horizontal waves returning also depends on the size of raindrops. Because the raindrops are getting bigger and bigger, they will become flatter and flatter. Scientists can also distinguish big raindrops from hail, because hail is more round than hamburger-shaped raindrops.

Doppler radar is still improving, and discoveries are constantly emerging. Since the late 1980s, storm trackers have been using portable Doppler radar to discover the subtle changes of the wind formed by the original tornado clouds. Since 1996, the tracker has brought the radar into the interior of the hurricane and detected the fascinating wind rotation that previous instruments could not detect. The newly revealed phenomenon remains to be explained.