Simultaneous Observations of Cloud and Precipitation Particles with Vertically Pointing X-Band and Ka-Band Radars

The backscattered energy received at a radar from a cloud is proportional to several parameters which include peak power, antenna constants, and ¿-4, where ¿ is the radar wavelength. The wavelengths of weather radars vary from centimeters to millimeters. In theory, all such radars should be able to detect both cloud and precipitation particles but, because of practical limitation on antenna size and power output, only the shortest wavelength weather radars are sensitive to the full range of sizes covered by these particles (0.01 mm to over 5 mm in dimensions) which can produce echoes ranging over 160 dB. Simultaneous observations of cloud and precipitation systems with X-band (3-cm wavelength) and Ka-band (0.86-cm wavelength) radars provide the needed realizable dynamic range. Simultaneous measurements of this type are described and are shown to reveal the locations within clouds where precipitation is developing and the growth of precipitation with fall distance, as well as providing continuous measurements of cloud top heights. The inadequacy of X-band radars to measure cloud top heights is demonstrated.