1:45 PM - 3:15 PM
[MIS23-P06] Analytical study of volcanic eruptions by using dual polarization radar: 2nd report
Keywords:dual polarization radar, volcanic eruption plume, remote sensing
The Kagoshima Local Meteorological Office is working with the Department of Volcanology Research of the Meteorological Research Institute on an analytical study of volcanic plumes using dual polarization (dual-pol) radar. We will introduce the results (2nd report) of the study.
Currently, volcanic plume observations by the Japan Meteorological Agency (JMA) are mainly based on images from distant cameras. Therefore, it is impossible to observe the height and volume of volcanic plumes when the area near the crater is covered by clouds. However, if weather radar can be used for immediate volcanic plume observation, it will be possible to observe volcanic plumes in such cases as well. It is also expected to improve the initial values used in ashfall forecasts issued by JMA.
In general, it is difficult to distinguish between plumes and rain clouds in rainy condition only with the information obtained from conventional single-pol radar. On the other hand, by using dual-pol radar, it is expected that more information on target particles, i.e., information for discriminating between plumes and rain clouds, can be obtained.
Comparing an explosive eruption on a clear day with an explosive eruption on a cloudy day, we obtained the data suggesting that the fallout was water-induced aggregates of volcanic ash. We also found that immediately after the eruption, the ρhv of the plume was smaller than that of the precipitation echoes. This information would be useful for discriminating a plume echo from surrounding precipitation echoes immediately after an eruption.
In future, more case analyses should be conducted to find out what values the radar parameters of volcanic plumes can take during each weather event.
Currently, volcanic plume observations by the Japan Meteorological Agency (JMA) are mainly based on images from distant cameras. Therefore, it is impossible to observe the height and volume of volcanic plumes when the area near the crater is covered by clouds. However, if weather radar can be used for immediate volcanic plume observation, it will be possible to observe volcanic plumes in such cases as well. It is also expected to improve the initial values used in ashfall forecasts issued by JMA.
In general, it is difficult to distinguish between plumes and rain clouds in rainy condition only with the information obtained from conventional single-pol radar. On the other hand, by using dual-pol radar, it is expected that more information on target particles, i.e., information for discriminating between plumes and rain clouds, can be obtained.
Comparing an explosive eruption on a clear day with an explosive eruption on a cloudy day, we obtained the data suggesting that the fallout was water-induced aggregates of volcanic ash. We also found that immediately after the eruption, the ρhv of the plume was smaller than that of the precipitation echoes. This information would be useful for discriminating a plume echo from surrounding precipitation echoes immediately after an eruption.
In future, more case analyses should be conducted to find out what values the radar parameters of volcanic plumes can take during each weather event.