4:00 PM - 4:15 PM
[SVC31-19] Monitoring of sulfur dioxide flux by using the TROPOMI sensor mounted on Sentinel-5p satellite and JMA Local Analysis, and volcanic activity of Nishinoshima island
Keywords:sulfur dioxide flux, TROPOMI, Nishinoshima, JMA Local Analysis
It is indispensable to watch the magma activity through the sulfur dioxide flux for volcanic monitoring, whether during eruption or not eruption (Kazahaya and Mori, 2016). It is more efficient to watch sulfur dioxide by satellite observations than ground-based observations, for large-scale eruptions or island volcano eruptions.
TROPOMI sensor onboard Sentinel-5 Precursor (Veefkind et al., 2012), launched as a polar orbiting satellite by the European Space Agency, has taken an image of the slant column molar density (SCD) of sulfur dioxide every day since 2018. Meanwhile regarding the method of understanding the advective diffusion of sulfur dioxide, Pardini et al. (2018) carried out research and development and Queißer et al. (2019) have applied this method to the TROPOMI data and published a study on the sulfur dioxide emission activity of Etna volcano.
In this study, we tried to estimate the sulfur dioxide emission rate by using the meteorological local analysis (LA) of Japan Meteorological Agency, which is detailed around Japan, based on the quasi method of Pardini et al. (2018). We traced back the hourly trajectory of grids with SCD of more than 0.0025 mol/m2 at an altitude of more than 1 km using the LA back-trajectory analysis, and estimated the emission rate per day assuming that grids returned around Nishinoshima was the sulfur dioxide emitted from Nishinoshima. Although the ratio of the total grids that did not return to Nishinoshima was around 40 % on average, the ratio of the total moles of grids that did not return was 3 %, indicating that most of the SO2 grids have been captured by this analysis. In addition, the capture rate from this analysis was even lower beyond seven hours from the initial time (shooting time). The reason for this is presumed to be the expansion of the initial value error. In addition, the reason for the decrease in the SCD of the trapped grids around Nishinoshima is presumed to be that sulfur dioxide diffuses over time and the number of detectable grids decreases. Therefore, the calculation of the emission rate was taken as an average for seven hours from the initial time.
We calculated the sulfur dioxide emission rate of Nishinoshima using this method. Sulfur dioxide began to be detected around July 2022, and the emission rate increased in late September, exceeded 10,000 tons per day in early October, and then declined. As of January 2023, it remains at 1,000 tons per day. The total sulfur dioxide release from the current eruptive activity (since July 2022) is 110,000 tons, much larger than the 5,000 tons from the previous August 2021 eruptive activity. However, it is much smaller than the 850,000 tons of 2019-2020 eruptive activity. During the period from 2014 to 2018, when large amounts of lava erupted and shaped present-day Nishinoshima, sulfur dioxide emission rates were less than 1,000 tons per day, according to shipboard observations (Takagi, 2018). From the above, it is possible that the large amount of sulfur dioxide generation system that was established in 2019 is still being maintained.
TROPOMI sensor onboard Sentinel-5 Precursor (Veefkind et al., 2012), launched as a polar orbiting satellite by the European Space Agency, has taken an image of the slant column molar density (SCD) of sulfur dioxide every day since 2018. Meanwhile regarding the method of understanding the advective diffusion of sulfur dioxide, Pardini et al. (2018) carried out research and development and Queißer et al. (2019) have applied this method to the TROPOMI data and published a study on the sulfur dioxide emission activity of Etna volcano.
In this study, we tried to estimate the sulfur dioxide emission rate by using the meteorological local analysis (LA) of Japan Meteorological Agency, which is detailed around Japan, based on the quasi method of Pardini et al. (2018). We traced back the hourly trajectory of grids with SCD of more than 0.0025 mol/m2 at an altitude of more than 1 km using the LA back-trajectory analysis, and estimated the emission rate per day assuming that grids returned around Nishinoshima was the sulfur dioxide emitted from Nishinoshima. Although the ratio of the total grids that did not return to Nishinoshima was around 40 % on average, the ratio of the total moles of grids that did not return was 3 %, indicating that most of the SO2 grids have been captured by this analysis. In addition, the capture rate from this analysis was even lower beyond seven hours from the initial time (shooting time). The reason for this is presumed to be the expansion of the initial value error. In addition, the reason for the decrease in the SCD of the trapped grids around Nishinoshima is presumed to be that sulfur dioxide diffuses over time and the number of detectable grids decreases. Therefore, the calculation of the emission rate was taken as an average for seven hours from the initial time.
We calculated the sulfur dioxide emission rate of Nishinoshima using this method. Sulfur dioxide began to be detected around July 2022, and the emission rate increased in late September, exceeded 10,000 tons per day in early October, and then declined. As of January 2023, it remains at 1,000 tons per day. The total sulfur dioxide release from the current eruptive activity (since July 2022) is 110,000 tons, much larger than the 5,000 tons from the previous August 2021 eruptive activity. However, it is much smaller than the 850,000 tons of 2019-2020 eruptive activity. During the period from 2014 to 2018, when large amounts of lava erupted and shaped present-day Nishinoshima, sulfur dioxide emission rates were less than 1,000 tons per day, according to shipboard observations (Takagi, 2018). From the above, it is possible that the large amount of sulfur dioxide generation system that was established in 2019 is still being maintained.