The principle of weather radar

Weather radar is mostly pulse radar, which emits pulse waves with short duration (0.25 ~ 4 microseconds) at a certain repetition frequency, and then receives echo pulses scattered by precipitation particles. The scattering and absorption of radar waves by precipitation are related to the characteristics of raindrop spectrum, rainfall intensity, the phase state of precipitation particles and the shape and orientation of ice crystal particles (see microwave scattering of clouds and precipitation particles, microwave absorption of clouds and precipitation particles). Therefore, through the analysis and judgment of precipitation echo, we can determine various macro and micro physical characteristics of precipitation. Various theoretical and empirical relationships have been established between echo power and precipitation intensity. Using these relations, the distribution of precipitation intensity and total precipitation within the radar detection range can be determined according to the echo power (see radar precipitation measurement).