Simultaneous Detection and Comparison for a Ka-band MM-Wavelength Cloud Radar with an X-band Polarimetric Radar

A series of campaigns of simultaneous detection are conducted for evaluating detecting capability of a Ka-band mm-wavelength cloud radar, of which attenuation in a variety of clouds or light rain events are focally analyzed and discussed. This cloud radar belongs to the Institute of Heavy Rain (IHR), China Meteorological Administration, Wuhan and was employed in 2010. During July 2010, several cases such as non precipitation clouds and light rainfall events, which occurred in a coastal region of the South China Sea, were simultaneously detected by the cloud radar and a X-band polarimetric radar located together at the same site. Through comparing and analyzing the dataset of the radars, some performances about detecting capability of the mm-wavelength cloud radar are evaluated. In convective cloud cases, which include both cumulus and cumulonimbus, the two radars are consistent with detection in the spatial distributions of echo intensity and Doppler radial velocity, but there are obvious differences in linear depolarimetric ratio (LDR) and Doppler spectral width. The similar result is obtained in analysis of correlation for the measurements mentioned above by diagnosing scatter diagrams of the radar measurements at the same location in the cloud echo. Compared to the X-band polarimetric radar, the attenuation in convective cloud of the mm-wavelength radar is significant. In a Cb cloud case, the attenuation of the cloud radar becomes more severe and its echo intensity is less 5 to 20dBZ than that of the X-band radar within 10-20km away from the radar station. On the other hand, the reflectivity, which detected by cloud radar, in cloud marginal area close to the radar station is greater than that of X-band radar. In non precipitation cloud cases the cloud radar detects not only similar spatial characteristic of measurements with the X-band radar, but also it has higher sensitivity for backscatter power of cloud droplet and data resolution in time and space. Within effective detecting range of the cloud radar, it is capable to identify various kinds of cirrus (Ci, Cs,Cc) and their profiling characteristics in these cases. Furthermore, the attenuation of the mm-wavelength radar in several types of non precipitation clouds is estimated in quantity by utilizing radio sounding data and the X-band radar data. In conclusion, the Ka-band mm-wavelength cloud radar of IHR is capable to reliably detect non precipitation and light rain clouds and its attenuation in cloud should be processed carefully, especially in convective cloud case.