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[MIS16-01] Observations of Volcanic Eruption Columns with Different Types of Weather Radars
Keywords:X-band marine radar, Ku-band rapid scanning Doppler radar, X-band polarimetric radar
Utilizing these different types of radar data, we perform detailed analysis of eruption columns. The marine radar succeeded in detecting eruptions and at the same time detecting falling pyroclastic particles (Fig. 1). The radar also reveals the fine structure of an ascending eruption column at 1.25-second intervals. While the marine radar observes volcanic ash columns with the wider azimuth angel resolution 22° due to its fan beam antenna, Ka-band Doppler radar can observe the targets with finer azimuthal resolution using RHI scanning of the parabolic antenna. The Ka-band radar RHI observations also reveal the upward speed of the ash echo top at 2-minute intervals. While both the marine radar and the Ku-band Doppler radar measure eruption column vertically at a fixed azimuthal direction, the Ku-band Doppler radar measures all azimuth and elevation angles every 1 minute. Using this scanning strategy, we can clarify the temporal change of the eruption column during its downwind movement: the radar reflectivity factor of the upper part of the eruption column becomes high 5-minute after the eruption, which is probably due to the aggregation process in water clouds (Fig. 2). The operational X-band MP radar collects 20 tilts PPI scan data at 5-minute interval. We can construct three-dimensional data of ash clouds with time and spatial interpolation method. Then we can obtain the wide-area ash fall distributions.
In conclusion, as mentioned above, different types of weather radars are now available for studying volcanic eruption columns and their applications to disaster prevention are promising.