Clear-Air Echoes: A Study of Radar Signals in Cloud-Free Atmospheres

One phenomenon of interest is clear-air echo observed by weather radar from a region of the atmosphere with no apparent meteorological scatterers such as clouds or precipitation. Since the deployment of the weather radar (CINRAD) after World War II, a huge area of clear-air echo is observed every night during the flood season. It is generally accepted that two mechanisms, turbulence scattering mechanisms caused by turbulent inhomogeneities and biological scatterers exemplified by insects and birds, dominate the scattering process of clear-air echoes (Chen et al., 2015).

Reference:

Chen, H., Li, Y., Guo, W., Zhang, Y., & Chen, H. (2015). Characteristics of clear-air echoes observed by S-band radar in Shenzhen, China. Journal of Atmospheric and Solar-Terrestrial Physics, 122, 112-120. https://doi.org/10.1016/j.jastp.2014.12.004