Author(s): Magfira Syarifuddin; Mariko Ogawa; Haruhisa Nakamichi; Satoru Oishi; Masato Iguchi
Linked Author(s): Satoru Oishi
Keywords: X-MP radar; Radar-based rain rate estimate; The heavy rain of July 2018; Kagoshima
Abstract: Japan experienced a breaking-record rainfall event from Western Japan to the Tokai region from 28 June to 8 July 2018. This paper analyzes the peak rainfall of this event on 6-8 July 2018 in Kagoshima by a small-compact X-band Multi-Parameter (MP) radar. The aim of this paper is to know the reliability of the rain rate estimated by the radar during the extreme rainfall event. The estimated rain rate provided by the X -MP radar using an unknown algorithm (Furuno) is compared to three different radar algorithms based on radar reflectivity factor (ZH), specific differential phase shift (KDP), and differential reflectivity (ZDR). The estimated radar-based rain rate at 500m height is then compared to the ground-based rain measured by a rain gauge. The KDP-ZH -based rain algorithm gives the closest values to the unknown Furuno algorithm, which indicates the use of KDP parameter as the rain rate estimator. The spatial information of radar is able to monitor more than 250 mm rain depth, which cannot be obtained by the rain gauge. In general, the point-based comparison between hourly radar-based rain rate and ground-based rain rate shows a similar temporal fluctuation, but in general, most of the values on 7 July 2018 fall below the rain gauge measurement. The estimated Furuno rain rate and the ZHH- KDP -based algorithm gives the closest values to the increase of ground-based rain depth at 1:0.94 and 1:0.89 ratios, respectively, while the ZHH-ZDR -based algorithm has the lowest ratio of 1:0.79.