Copernicus 35 GHz cloud radar
10 Mar 2011



Copernicus is a 35 GHz (9 mm wavelength) cloud radar. It is a fully coherent, dual-polarisation, pulse compression Doppler radar.




It is currently installed on a ground fixed pedestal with a 2.4 m parabolic antenna. The radar complements the 94 GHz (3 mm) "Galileo" cloud radar at the Observatory for observations of cloud microphysics and climatology. The radar provides real-time measurement and display of the full Doppler spectrum, and the moments Z, ZDR, LDR, v, w, phiDP, and KDP. The latest results from Copernicus can be viewed on the Chilbolton weather web.

Millimetre-wave cloud radars exploit the fact that the echo intensity of Rayleigh scatter increases with the inverse-fourth power of the wavelength. These radars normally operate in the windows in the atmospheric absorption spectrum at 35 GHz and 94 GHz.

Operating the two radars in parallel allows dual-wavelength observations. Dual-wavelength cloud radar measurements make it possible to determine the liquid water content and ice water content of clouds, using the dual-wavelength ratio (DWR). The liquid water content (LWC) can be derived by exploiting the fact that attenuation by liquid water in clouds is dependent on frequency.

The shorter-wavelength radar (94 GHz) is sensitive to a small amount of Mie scattering from the largest cloud particles. The 35 GHz backscatter, however, is overwhelmingly due to the Rayleigh mechanism. Therefore, the DWR provides a measure of the size of the scattering particles. Together with measurements of radar reflectivity, this allows ice water content to be derived in cirrus clouds.

Technical specifications of the Copernicus radar

Contact: Jeffery, Judith (STFC,RAL,RALSP)