5:15 PM - 7:15 PM
[MTT38-P07] Mobile observation of the Sakurajima eruption cloud when PPI observation was added
Keywords:Mobile observation of the Sakurajima eruption, Marine RADAR, PPI
Preface
The general eruption cloud observation of the volcano is conducted in three-dimensional meteorological radar, and pencil beam is used. When the meteorological radar is observed in a spiral, observing time from five minutes to around ten minutes is taken, but it can be expected that the marine radar observes the motion of the volcanic smoke in the period when it is had a shorter than meteorological radar because fan beam can observe turn in the high speed for 2.5 seconds. In addition, gravity is around 20 kg and slightly solid one, and the marine radar is suitable for mobile observation. From 2018 including observation of the eruption cloud of Sakurajima mainly Sakurajima observatory (SVO: RHI (Range Height Indicator) observation was continued in Sakurajima volcano observatory) and Kurokami .
Detail could measure vertical direction of the eruption cloud in the RHI observation, but because the horizontal direction of movement was hard to be caught, the horizontal displacement of the volcanic smoke could be grasped by adding PPI (Plan Position Indicator) observation to Kurokami, or PPI observation was investigated and got the record which eruption cloud horizontally moved.
Method
PPI observation was added to Kurokami on May 14, 2024, and horizontal displacement of the eruption cloud was observed. RHI observes MinamiDake in marine radar in western SVO of Sakurajima that has been already established and Kurokami of the east side.
Beam angle is 11° on the plane from a plane in the PPI observation. Because the MinamiDake summit (13°) is not reached. 25° was made with the jig which added elevation angle to antenna, and it was 36° - 14° from a plane and came to be able to observe beam width (-3dB) over MinamiDake. The use frequency band of the marine radar is X-band, Horizontal beam width 1.2°, Vertical beam width 22°, The antenna length 195cm (6ft), Radar for the PPI of Kurokami is solid state radar, Radar for the RHI is magnetron radar. And marine radar of SVO is RHI observation in solid state radar.
Result
The center of the image is Kurokami, Mountain slope of Sakurajima appears in the top, and MinamiDake crater becomes the shadow on the mountain slope left side. In the case of antenna elevation angle 0 °, the beam width for upper parts becomes 11°. Because an elevation angle to face MinamiDake from Kurokami is 13°, the intensity of the mountain slope image becomes strong. Therefore, the result that an elevation angle of the antenna was raised by 25°, and rise and fall way beam width became 14° - 36°.
Elevation angle 25° becomes small the image area of the hillside at elevation angle 0° and 25°. When a strong part of the signal strength is read in path of MinamiDake, it is expected by Kurokami that eruption cloud can be observed well because 7.7dB - 3.9dB (standard deviation 2.0-3.4) is lower than 0 ° as for elevation angle 25 ° on the average.
There was three times of eruption more than 2,000m on July 23 from May 14, 2024 of the observation period, and it was eruption at 2024/7/14 18:19 that PPI observation showed effect most.
There was an echo in the crater just after eruption in the PPI observation result, and eruption cloud drifted to the NE way afterwards, and eruption cloud drifted from crater to around 8km through north of Kurokami.
Summary
Marine radar was set up in SVO and Kurokami to observe a change of the eruption cloud vertical direction in marine radar, and RHI was observed. It was examined that PPI observation was added to demand a current direction of the eruption cloud not to understand in the RHI observation. From Kurokami in to MinamiDake and distance of equivalent 4km, as for the RHI and the horizontal plane beam of the PPI, 22° of the RHI is 1,536m, 1.2° of the PPI is 84m. Resolution of the PPI was good and was able to catch the way which flowed of the eruption cloud. The effect that ground clutter of the mountain slope reduced when an elevation angle of the PPI was made 25 ° from 0 ° was confirmed.
Acknowledgement
This research received the furtherance of the Ministry of Education, Culture, Sports, Science and Technology "next-generation volcano research, personnel development general project" (task 22K03760) and Institute for Kyoto University disaster prevention public collaboration received the furtherance of "the radar multi-sensing research of the extreme phenomenon".
The general eruption cloud observation of the volcano is conducted in three-dimensional meteorological radar, and pencil beam is used. When the meteorological radar is observed in a spiral, observing time from five minutes to around ten minutes is taken, but it can be expected that the marine radar observes the motion of the volcanic smoke in the period when it is had a shorter than meteorological radar because fan beam can observe turn in the high speed for 2.5 seconds. In addition, gravity is around 20 kg and slightly solid one, and the marine radar is suitable for mobile observation. From 2018 including observation of the eruption cloud of Sakurajima mainly Sakurajima observatory (SVO: RHI (Range Height Indicator) observation was continued in Sakurajima volcano observatory) and Kurokami .
Detail could measure vertical direction of the eruption cloud in the RHI observation, but because the horizontal direction of movement was hard to be caught, the horizontal displacement of the volcanic smoke could be grasped by adding PPI (Plan Position Indicator) observation to Kurokami, or PPI observation was investigated and got the record which eruption cloud horizontally moved.
Method
PPI observation was added to Kurokami on May 14, 2024, and horizontal displacement of the eruption cloud was observed. RHI observes MinamiDake in marine radar in western SVO of Sakurajima that has been already established and Kurokami of the east side.
Beam angle is 11° on the plane from a plane in the PPI observation. Because the MinamiDake summit (13°) is not reached. 25° was made with the jig which added elevation angle to antenna, and it was 36° - 14° from a plane and came to be able to observe beam width (-3dB) over MinamiDake. The use frequency band of the marine radar is X-band, Horizontal beam width 1.2°, Vertical beam width 22°, The antenna length 195cm (6ft), Radar for the PPI of Kurokami is solid state radar, Radar for the RHI is magnetron radar. And marine radar of SVO is RHI observation in solid state radar.
Result
The center of the image is Kurokami, Mountain slope of Sakurajima appears in the top, and MinamiDake crater becomes the shadow on the mountain slope left side. In the case of antenna elevation angle 0 °, the beam width for upper parts becomes 11°. Because an elevation angle to face MinamiDake from Kurokami is 13°, the intensity of the mountain slope image becomes strong. Therefore, the result that an elevation angle of the antenna was raised by 25°, and rise and fall way beam width became 14° - 36°.
Elevation angle 25° becomes small the image area of the hillside at elevation angle 0° and 25°. When a strong part of the signal strength is read in path of MinamiDake, it is expected by Kurokami that eruption cloud can be observed well because 7.7dB - 3.9dB (standard deviation 2.0-3.4) is lower than 0 ° as for elevation angle 25 ° on the average.
There was three times of eruption more than 2,000m on July 23 from May 14, 2024 of the observation period, and it was eruption at 2024/7/14 18:19 that PPI observation showed effect most.
There was an echo in the crater just after eruption in the PPI observation result, and eruption cloud drifted to the NE way afterwards, and eruption cloud drifted from crater to around 8km through north of Kurokami.
Summary
Marine radar was set up in SVO and Kurokami to observe a change of the eruption cloud vertical direction in marine radar, and RHI was observed. It was examined that PPI observation was added to demand a current direction of the eruption cloud not to understand in the RHI observation. From Kurokami in to MinamiDake and distance of equivalent 4km, as for the RHI and the horizontal plane beam of the PPI, 22° of the RHI is 1,536m, 1.2° of the PPI is 84m. Resolution of the PPI was good and was able to catch the way which flowed of the eruption cloud. The effect that ground clutter of the mountain slope reduced when an elevation angle of the PPI was made 25 ° from 0 ° was confirmed.
Acknowledgement
This research received the furtherance of the Ministry of Education, Culture, Sports, Science and Technology "next-generation volcano research, personnel development general project" (task 22K03760) and Institute for Kyoto University disaster prevention public collaboration received the furtherance of "the radar multi-sensing research of the extreme phenomenon".