Vertical Rain Attenuation Characteristics of Ka- and Ku-band observed by the 400-MHz Wind Profiler

The 400-MHz wind profiler (400-MHz WPR) is able to observe simultaneously the atmospheric turbulence echo and the echo from precipitation. Therefore, by analyzing the echo power spectrum of the received signal, the raindrop size distribution can be estimated for which the effects of wind speed, the intensity of atmospheric turbulence, and background winds have been removed. Several methods have been proposed to estimate raindrop size distribution (DSD) from the UHF/VHF Wind Profiler data. The DSD below the melting layer observed by the 400-MHz WPR is basically retrieved by a non-parametric method. In order to evaluate and improve the accuracy of rainfall intensity from space-borne radars (TRMM/PR and GPM/DPR), it is important to estimate the rain attenuation, namely the k-Z relationship (k is the specific attenuation, Z is the radar reflectivity) correctly. Intensive field observations for subtropical precipitation using 400-MHz WPR, COBRA (C-band polarimetric radar), and 2D-Video distrometer (2DVD) were carried out during the month of June in 2007, 2008, and 2009 at Okinawa island, Japan. These instruments are part of the Okinawa Sub-tropical Environment Remote Sensing Center, operated by the National Institute of Information and Communication Technology (NICT). During field observations, there were several rain events. Using these vertical raindrop size distributions, the extinction cross section and the back scattering cross section can be processed by the Mie scattering theory. Then, the specific attenuation (k) and the radar reflectivity (Z) for Ka- and Ku-band are estimated. The vertical variations and characteristics (depending on rain type) of rain attenuation for Ka- and Ku-band can be analyzed. The GPM/DPR and TRMM/PR algorithm can be also evaluated using these results.