What is the working principle of cloud radar?

Cloud radar emits pulsed radio waves into space through a highly directional antenna, and interacts with the atmosphere during the propagation. The scattering effect of raindrops, cloud droplets, ice crystals and snowflakes on electromagnetic waves is used to detect the concentration, distribution, movement and evolution of precipitation or large water droplets in the atmosphere and understand the structure and characteristics of weather systems.

working range

It is mainly used to detect the height of cloud top and cloud bottom. If there are more than one cloud in the sky, the height of each layer can be measured. Because cloud particles are smaller than precipitation particles, the working wavelength of cloud radar is shorter. Cloud radar can only detect middle and high-level clouds with less clouds. For low-level clouds with high water content, such as cumulonimbus clouds and hail, the beam of cloud radar is difficult to penetrate and can only be detected by rain radar.

data processing

Measurement of target azimuth and elevation: The measurement of target azimuth and elevation depends on the directivity of antenna. The antenna of weather radar has strong directivity, which can concentrate the energy of detection pulse and emit it in a certain direction. Similarly, it can only receive echo signals from the same direction. Therefore, only by aiming the antenna at the target can the echo signal of the target be received. According to this principle, when the target is found, the azimuth and elevation of the antenna are the azimuth and elevation of the target relative to the radar.

Measurement of target characteristics: the scattering of radar electromagnetic waves by meteorological targets is the basis for radar to detect the atmosphere.

Precipitation echo: Scattering of clouds and precipitation particles. According to the phase and geometry, the radar echo power is generated by all meteorological targets in the effective illumination volume.

Clear sky echo: echo is detected in a cloudless area or a cloud area composed of extremely small particles in the atmosphere. There are two kinds of meteorological conditions: one is that there is an area with uneven refractive index in the atmosphere, that is, the turbulent atmosphere causes the scattering of radar waves; Second, there is a region with a large vertical gradient of refractive index in the stratified atmosphere, that is, the atmosphere causes specular reflection of radar waves.