Abstract
Since 2015, collaborative research conducted by Indonesian and Japan scientists has initiated the installation of small X-band Multi-Parameter (X-MP) radars to mitigate the occurrence of rainfall-induced lahar in three active volcanoes in Indonesia and Japan: Merapi, Sinabung, and Sakurajima. This paper discusses the technical aspects of data acquisition, processing, and performance of the X-MP radar at the Merapi and Sakurajima volcanoes by comparing the estimated rainfall intensity acquired by the radar to three empirical radar-rainfall algorithms. The algorithms are based on radar reflectivity factor (ZHH), specific differential phase shift (KDP), and differential reflectivity (ZDR). A new method of Constant Altitude Plan Position Indicator (CAPPI) interpolation by linear regression is also proposed for a more efficient computation. The first algorithm by Marshall-Palmer, which relies on ZHH, gave the lowest average and maximum rainfall values compared with the other algorithms for all rainfall event cases. On the other hand, the other two algorithms, which involve the MP of radar by Bringi and Chandrasekar and Park et al., gave closer rainfall intensity values with the estimated rainfall intensity acquired by the X-MP radar. These three rain rates give a closer temporal fluctuation when they are compared to the rain gauge-based rainfall intensity.
Highlights
One of the deadliest hazards in volcanic regions is rainfall-induced lahar
Both radars are dual-polarimetry radars that give multi-parameters, which is believed to improve the accuracy of quantitative precipitation estimate (QPE)
It is apparent that the rain map data provided by the X-band Multi-Parameter (X-MP) radar at Mt
Summary
One of the deadliest hazards in volcanic regions is rainfall-induced lahar. Published under licence by IOP Publishing Ltd doi:10.1088/1755-1315/437/1/012040 highlighted the importance of higher spatial and temporal resolution rain data for higher precision in lahar risk monitoring and prediction [1], [2]. The challenging aspect of rainfall monitoring in volcanic areas lies in two main problems. Lahar usually occurs in a small area (less than 1 km) and is inaccessible. The rain gauge network for rainfall measurement usually covers the downstream area, while the initiation of lahar usually happens in the upstream area. For the Merapi volcano, lahar usually occurs at elevations higher than 1200 m above sea level (asl) [3]. For the Sakurajima volcano, it usually occurs at elevations of greater than 400 m asl [4]
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