Simultaneous Observations of Clouds and Precipitation using C-Band and Ka-Band Radar

The synergy of radars with different wavelength can provide additional information on the physics of clouds and precipitation. While C-band weather radars are not sensitive enough for small ice and water particles, almost no attenuation of the waves is observed for weak to medium precipitation. On the other hand, Ka-band cloud radars are sensitive enough to detect small ice and water particles. However, attenuation limits the ability to perform measurements in rain.

Synchronous RHI scans were performed with DLR’s dual-polarization C-band radar POLDIRAD and a Mira-36 Ka-band cloud radar operated at the University of Munich. The two radars are separated by a distance of about 23 km and have an overlapping measurement range of about 30 km.

Despite of a calibration offset both reflectivity measurements agree quite well in the reflectivity range between -10 to 10 dBz. For lower reflectivity values the measurements with the C-band radar are limited to short ranges. At reflectivity values above 15 dBz attenuation effects at Ka-band are visible. Interestingly in ice clouds the overlapping region of both radars is large and the C-band radar has a high detection efficiency in ice clouds. This gives evidence on the presence of larger ice particles were the backscatter is sufficient high enough due to the D^6 dependence.

For the presentation we will evaluate further microphysical properties using reflectivity differences caused by Rayleigh and Mie scatter as well as attenuation effects observed at Ka-band. Since the C-band radar has full polarization agility and the cloud radar can measure linear depolarization ratio LDR further diversification of cloud and precipitation is possible.