What is a weather radar chart?

About weather radar and radar charts

Basic overview Radar specially used for atmospheric detection. It is an active microwave atmospheric remote sensing equipment. High-altitude wind radar used in conjunction with radiosondes is only a specialized device for positioning displacement balloons and is generally not considered such a radar. Weather radar is one of the main detection tools used to warn and forecast medium- and small-scale weather systems (such as typhoons and heavy rain clouds). Conventional radar devices are generally composed of directional antennas, transmitters, receivers, antenna controllers, displays and camera devices, electronic computers and image transmission. Weather radar uses a wide range of radio wavelengths, from 1 centimeter to 1000 centimeters. They are often divided into different bands to represent the main functions of the radar. The commonly used wavelengths of 1, 3, 5, 10 and 20 cm in weather radar respectively correspond to K band (wavelength 0.75 ~ 2.4 cm), X band (wavelength 2.4 ~ 3.75 cm), C band (wavelength 3.75 ~ 7.5 cm) , S band (wavelength 7.5 ~ 15 cm) and L band (wavelength 15 ~ 30 cm), the wavelength range of UHF and VHF radar is 10 ~ 100 cm and 100 ~ 1000 cm respectively. The performance of radar in detecting atmospheric targets is closely related to its operating wavelength. Considering the scattering and absorption of radio waves by cloud and rain particles, various wave bands have only a certain range of application. K-band radar is commonly used to detect various clouds that do not produce precipitation. X, C and S-band radars are used to detect precipitation. The S-band is most suitable for detecting heavy rain and hail. Highly sensitive UHF and VHF radars can detect the troposphere. - Clear air flow field in the stratosphere-middle level.

Weather radar emits pulse radio waves into space through a highly directional antenna, which interacts with the atmosphere in various ways during propagation. Such as the scattering and absorption of radar emitted waves by water vapor condensates (clouds, fog and precipitation) in the atmosphere; the depolarization effect of non-spherical particles on the scattering of circularly polarized waves, the uneven structure of air refractive index of radio waves and lightning discharges The formed ionized medium scatters the incident wave, the stable stratified atmosphere partially reflects the incident wave; and the movement of the scattering target within the scattering volume causes the Doppler effect on the incident wave, etc. Weather radar echo can not only determine the macroscopic characteristics such as spatial position, shape, scale, movement and development changes of the detection target, but also determine various physical characteristics of the target based on the amplitude, phase, frequency and polarization of the echo signal. For example, water content in clouds, precipitation intensity, wind field, vertical airflow velocity, atmospheric turbulence, precipitation particle spectrum, cloud and precipitation particle phase states, and lightning, etc. In addition, the law of the refractive index changing with altitude caused by changes in tropospheric atmospheric temperature and humidity can also be used to calculate the vertical gradient of the refractive index from the detected vertical distribution of temperature and humidity in the troposphere, and through analysis The conditions for radio wave propagation can predict the radar detection range, and the stratification of atmospheric temperature and humidity can also be inferred based on anomalies in the radar detection range (such as superrefraction).

Classification: Radars without Doppler performance are called incoherent radars or conventional weather radars, and radars with Doppler performance are called coherent radars or Doppler radars. The main weather radars are: ① Cloud measuring radar. It is a radar used to detect the height, thickness and physical characteristics of clouds without precipitation. Its commonly used wavelengths are 1.25 cm or 0.86 cm. ? ②? Weather radar. It is a radar used to detect the occurrence, development and movement of precipitation, and to warn and track precipitation weather systems. ? ③? Circular polarization radar. General weather radars emit horizontally polarized waves or vertically polarized waves, while circularly polarized radars emit circularly polarized waves. When radar emits circularly polarized waves, the echo of spherical raindrops will be circularly polarized waves rotating in the opposite direction. Non-spherical large particles (such as hail) will cause depolarization of circularly polarized waves. Non-spherical hail can be used to detect circularly polarized waves. With the depolarization echo characteristics, circular polarization radar can be used to identify the presence of hail in the storm. ? ④? FM continuous wave radar. It is a radar that detects the boundary layer of the atmosphere. It has extremely high distance resolution and sensitivity and is mainly used to measure the fluctuations, wind and turbulence of the clear-sky atmosphere in the boundary layer (see Atmospheric Boundary Layer). ? ⑤? Weather Doppler radar. Radar that uses the Doppler effect to measure the radial velocity of cloud and precipitation particles relative to the radar. ? ⑥? VHF and UHF Doppler radar. Utilizes the uneven structure of the refractive index of the troposphere and stratosphere and the scattering of free electrons in the middle atmosphere to detect the horizontal wind profile, vertical airflow profile, atmospheric turbulence parameters, atmospheric stable stratification and Radar for atmospheric fluctuations, etc. ? Among the radars studied and tested, there are also dual-wavelength radar and airborne Doppler radar. Since the 1970s, the new development of synthetic aperture radar, which uses a small moving antenna to be equivalent to a large antenna composed of many stationary small antennas, will certainly accelerate the future development of airborne Doppler radar. Airborne Doppler radar is highly maneuverable and can be used to obtain high-resolution Doppler velocity profiles of convective storms.

You can detect the proximity of dangerous weather as soon as possible and take preventive measures in a timely manner