Keywords:volcanic ash plume, weather radar
At Shimmoe-dake, eruptions occured in October 2017, and at Kusatsu-Shirane in January, 2018. During the Shimmoe-dake eruptions, we sometimes failed to monitor the volcanic ash plume in cloudy or rainy days. As for the Kusatsu-Shirane case, Mt. Moto-Shirane wasn't targeted by cameras around Kusatsu-Shirane in the first place. In such circumstances, weather radar is effective for monitoring active volcanoes. However, there are two big problems with this method with conventional weather radars. One is an error of radar echo height against actual volcanic ash plume height. The other is inability in quantitative ash amount estimation inside volcanic ash plume. The former can be improved by ray tracing with numerically calculated refractivity of Local Analysis (LA) made by JMA. In order to solve the latter problem, we have to use advanced weather radar such as polarimetric radar, and furthermore, a large amount of data will be needed. In this presentation, the results of radar analysis and future prospects for the method will be presented.