Presentation Information
[AAS14-P05]Precipitation measurement and raindrop size distribution estimation using a portable rainfall sensor
*Yuto Sampei1, Masaru Inatsu2, Shiho Onomura3, Ryuta Sakaguchi1, Kazuki Nanko4, Atsushi Hamada5, Shinta Seto6 (1.Graduate School of Science, Hokkaido University, 2.Faculty of Science, Hokkaido University, 3.Tokyo City University, 4.Tokyo University of Agriculture and Technology, 5.University of Toyama, 6.University of Nagasaki)
A newly developed, low-cost, portable, and low-maintenance rainfall sensor was evaluated through field observation at Nagasaki University, Kyushu, Japan. The observation was performed intermittently from 29 May to 14 October 2025, during which a wide range of precipitation intensities were recorded under the influence of the Baiu front and typhoon passages. The sensor recorded voltage signals reflecting microwave scattering by raindrops on the shield just above the sensor with a sampling rate of 3 kHz. It was found that the high-pass filtered output voltage was highly correlated with rainfall intensity even for an intense rainfall event exceeding 70 mm/h. Moreover, a new inversion method was developed to estimate raindrop size distributions by assuming a gamma distribution. The parameters are optimally determined to fit the statistical properties of voltage fluctuations. The estimated raindrop size distributions were generally consistent with those observed by the reference disdrometer. These results demonstrate that the portable rainfall sensor is capable of measuring even disastrous rainfall and has a potential to estimate raindrop size distributions based on a parametric model.