16:00 〜 16:15
[AAS09-08] 衛星観測と前方流跡線解析を用いた火山ガス放出率推定
キーワード：火山ガス、二酸化硫黄 SO2、流跡線、数値予報モデル、Sentinel-5P TROPOMI
1. Introduction
To understand volcanic emissions of sulfur dioxide (SO2) from large-scale eruptions and marine volcanoes, we have been developing a method to estimate emission rates by combining the distribution of SO2 column concentrations obtained from the TROPOMI sensor on the Sentinel-5p satellite with forward trajectory analysis based on numerically simulated wind field data.
In this paper, we report the results of our attempt to estimate the temporal variation of the emission rate for the SO2 plume from Nishinoshima Island, which was observed by the Sentinel-5p satellite on June 28, 2020.
2. Numerical experiments
A numerical simulation was conducted using the Japan Meteorological Agency's Non-Hydrostatic Model (JMA-NHM) to generate wind field data to be referenced in the forward trajectory analysis. Tracer particles were emitted from Nishinoshima Island in the simulated wind field, taking into account uncertainties in the altitude of the SO2 emission source and the horizontal diffusion coefficient. The emission rate was estimated based on the calculation results that best reproduced the observed SO2 distribution in the four evaluation regions, which are sandwiched between concentric circles of 50-100 km, 100-150 km, 150-200 km, and 200-250 km radius centered on Nishinoshima Island. In general, the closer the evaluation region is to the emission point, the later the emission time corresponds to, and the farther away from the point, the earlier the emission time corresponds to. Here, as the representative emission time, we adopted the average time when the tracer particles in each evaluation region were emitted from the crater.
3. Results and Discussion
As a result, the emission rates at 04:24, 06:36, 08:42, and 10:24 AM (JST) on June 28 were estimated to be 4895, 5392, 4696, and 3102 tons/day, respectively. This temporal change is roughly consistent with the estimation by the alternative method that uses backward trajectory analysis combined with the SO2 column concentration obtained by the TROPOMI sensor (Queißer et al., 2019; Takagi and Shimbori, 2023 ). In our study, the release rates were determined at intervals of about two hours. The relationship between the estimation time interval and the spatial scale of an evaluation region will vary depending on the horizontal wind speed.
Acknowledgments
This work was partially supported by JSPS Grant-in-Aid for Scientific Research 23K03512.
References
Queißer, M., M. Burton,, N. Theys,, et al., 2019: TROPOMI enables high resolution SO2 flux observations from Mt. Etna, Italy, and beyond. Sci Rep 9, 957. https://doi.org/10.1038/s41598-018-37807-w
Takagi, A. and T. Shimbori, 2023: 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. JpGU2023, SVC31-19. https://confit.atlas.jp/guide/event/jpgu2023/subject/SVC31-19/detail
To understand volcanic emissions of sulfur dioxide (SO2) from large-scale eruptions and marine volcanoes, we have been developing a method to estimate emission rates by combining the distribution of SO2 column concentrations obtained from the TROPOMI sensor on the Sentinel-5p satellite with forward trajectory analysis based on numerically simulated wind field data.
In this paper, we report the results of our attempt to estimate the temporal variation of the emission rate for the SO2 plume from Nishinoshima Island, which was observed by the Sentinel-5p satellite on June 28, 2020.
2. Numerical experiments
A numerical simulation was conducted using the Japan Meteorological Agency's Non-Hydrostatic Model (JMA-NHM) to generate wind field data to be referenced in the forward trajectory analysis. Tracer particles were emitted from Nishinoshima Island in the simulated wind field, taking into account uncertainties in the altitude of the SO2 emission source and the horizontal diffusion coefficient. The emission rate was estimated based on the calculation results that best reproduced the observed SO2 distribution in the four evaluation regions, which are sandwiched between concentric circles of 50-100 km, 100-150 km, 150-200 km, and 200-250 km radius centered on Nishinoshima Island. In general, the closer the evaluation region is to the emission point, the later the emission time corresponds to, and the farther away from the point, the earlier the emission time corresponds to. Here, as the representative emission time, we adopted the average time when the tracer particles in each evaluation region were emitted from the crater.
3. Results and Discussion
As a result, the emission rates at 04:24, 06:36, 08:42, and 10:24 AM (JST) on June 28 were estimated to be 4895, 5392, 4696, and 3102 tons/day, respectively. This temporal change is roughly consistent with the estimation by the alternative method that uses backward trajectory analysis combined with the SO2 column concentration obtained by the TROPOMI sensor (Queißer et al., 2019; Takagi and Shimbori, 2023 ). In our study, the release rates were determined at intervals of about two hours. The relationship between the estimation time interval and the spatial scale of an evaluation region will vary depending on the horizontal wind speed.
Acknowledgments
This work was partially supported by JSPS Grant-in-Aid for Scientific Research 23K03512.
References
Queißer, M., M. Burton,, N. Theys,, et al., 2019: TROPOMI enables high resolution SO2 flux observations from Mt. Etna, Italy, and beyond. Sci Rep 9, 957. https://doi.org/10.1038/s41598-018-37807-w
Takagi, A. and T. Shimbori, 2023: 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. JpGU2023, SVC31-19. https://confit.atlas.jp/guide/event/jpgu2023/subject/SVC31-19/detail