The clear sky echo above the mixed layer is mainly composed of

The clear sky echo above the mixed layer is mainly caused by atmospheric refraction and scattering.

In the atmosphere above the mixed layer, due to the low atmospheric density, radio waves are easier to propagate. Due to the influence of atmospheric refraction and scattering, radio waves will bend and scatter during propagation, leading to the appearance of echoes. This echo is called clear sky echo or atmospheric echo. The intensity and shape of clear sky echo can provide information such as atmospheric stratification, humidity and precipitation, so it is of great significance in meteorological radar and other applications. Through the observation and analysis of clear sky echoes, we can better understand and predict the atmospheric changes and weather conditions.