The principle of weather radar

Weather radars are mostly pulse radars, which emit pulse waves with short duration (.25 ~ 4 microseconds) at a certain repetition frequency, and then receive 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, phase state of precipitation particles, shape and orientation of ice crystal particles (see microwave scattering of clouds and precipitation particles, microwave absorption of clouds and precipitation particles). Therefore, by analyzing and judging the precipitation echo, we can determine all kinds of macroscopic and microphysical characteristics of precipitation. Various theoretical and empirical relations have been established between the echo power of precipitation and precipitation intensity. By 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 measuring precipitation).