Regional and diurnal variations of rain attenuation obtained from measurement of raindrop size distribution over indonesia at Ku, Ka and W bands

The measured raindrop size distribution (DSD) and the International Telecommunication Union Radiocommunication Sector (ITU-R) model have been used to elucidate the regional and diurnal variations of rain attenuation in Indonesia, for Ku-band (13.6 GHz), Ka-band (35.6 GHz), and W-band (96 GHz) frequencies. The DSDs were measured by the Parsivel disdrometer at Kototabang (KT; 100.32°E, 0.20°S), Padang (PD; 100:27°E, 0:54°S), Pontianak (PT; 109:37°E, 0:00°S), Manado (MN; 124:92°E, 1:55°N) and Biak (BK; 136:10°E, 1:18°S). In general, PD, KT and PT have lower rain attenuation than those at MN and BK, for the same rainfall rate, due to lower concentration of small-sized drops at these sites as reported by a previous study. Considerable differences between the attenuation obtained from the DSD and the ITU-R model are observed at all locations, in particular for very heavy rainfall (R > 50 mm/h). For R < 50 mm/h, the specific rain attenuation of measured DSD is in fairly good agreement with that obtained from the ITU-R model. The specific rain attenuation obtained from the DSD shows diurnal variation, in agreement with a previous study at KT. The diurnal variation of rain attenuation is dependent on the operating frequency and rainfall rate. At KT and PT, the lowest rain attenuation for Ku-band is observed during 06-12 LT, but during this period the largest attenuation is observed for Ka-and W-bands. These phenomena may be due to the increasing role of small and medium-sized drops by increasing frequency. © 2017, Electromagnetics Academy. All rights reserved.