Using Himawari-8, estimation of SO2 cloud altitude at Aso volcano eruption, on October 8, 2016

Abstract

It is vital to detect volcanic plumes as soon as possible for volcanic hazard mitigation such as aviation safety and the life of residents. Himawari-8, the Japan Meteorological Agency's (JMA's) geostationary meteorological satellite, has high spatial resolution and sixteen observation bands including the 8.6 μm band to detect sulfur dioxide (SO 2 ). Therefore, Ash RGB composite images (RED: brightness temperature (BT) difference between 12.4 and 10.4 μm, GREEN: BT difference between 10.4 and 8.6 μm, BLUE: 10.4 μm) discriminate SO 2 clouds and volcanic ash clouds from meteorological clouds. Since the Himawari-8 has also high temporal resolution, the real-time monitoring of ash and SO 2 clouds is of great use. A phreatomagmatic eruption of Aso volcano in Kyushu, Japan, occurred at 01:46 JST on October 8, 2016. For this eruption, the Ash RGB could detect SO 2 cloud from Aso volcano immediately after the eruption and track it even 12 h after. In this case, the Ash RGB images every 2.5 min could clearly detect the SO 2 cloud that conventional images such as infrared and split window could not detect sufficiently. Furthermore, we could estimate the height of the SO 2 cloud by comparing the Ash RGB images and simulations of the JMA Global Atmospheric Transport Model with a variety of height parameters. As a result of comparison, the top and bottom height of the SO 2 cloud emitted from the eruption was estimated as 7 and 13-14 km, respectively. Assuming the plume height was 13-14 km and eruption duration was 160-220 s (as estimated by seismic observation), the total emission mass of volcanic ash from the eruption was estimated as 6.1-11.8 × 10 8 kg, which is relatively consistent with 6.0-6.5 × 10 8 kg from field survey. Keywords

Aso volcano eruption on October 8, 2016, observed by weather radars

“…This result implies that the radar echo top altitude by JMA may be overestimated. In addition, the median value is lower than 13-14 km ASL, the top altitude of SO 2 cloud estimated by Himawari-8 Ash RGB and the JMA Global Atmospheric Transport Model by Ishii et al (2018). However, the result of our method is almost equal to 39,000 feet (11.9 km) ASL, which was derived by Himawari-8 infrared bands (Tokyo VAAC 2016).…”

Monitoring the Agung (Indonesia) Ash Plume of November 2017 by Means of Infrared Himawari 8 Data

“…An example is reported in Figure 7a, displaying the ash RGB product of 25 November at 22:00 UTC (see the RST ASH map of the same day and hour reported in ). The figure shows that volcanic ash, which should appear in pinkish color (see [25,27]), was difficult to be distinguished from the background (see region magnified at the top right side of the image). As can be seen from Figure 7b, modifying the Red component, i.e., analyzing the BT 11.2 − BT 10.4 spectral difference in place of BT 12.4 − BT 10.4 , the ash plume was more recognizable but at the expense of an increase of misleading features, which were mostly associated to meteorological clouds (e.g., see pink areas outside the region marked in black).…”

“…The improved features of the AHI instrument, in terms of spectral, spatial and temporal resolution, should guarantee a more efficient monitoring of rapidly changing weather/environmental phenomena in comparison with imagers of the previous MTSAT series [18]. In particular, the AHI infrared bands 7 (3.74-3.96 µ m), 11 (8.44-8. Although a number of studies up to now have been performed exploiting Himawari-8 observations (e.g., [21][22][23][24]), only a few of them focused on volcanic ash (e.g., [25,26]). Some authors In this work, we investigate the ash events of 25-28 November 2017 from space by implementing the well-established RST ASH algorithm [14][15][16], which was previously tested over the Asiatic region using infrared MTSAT-1R/2 (Multi-Functional Transport Satellite-1R/2) observations [17], for the first time on Himawari-8 data.…”

“…The improved features of the AHI instrument, in terms of spectral, spatial and temporal resolution, should guarantee a more efficient monitoring of rapidly changing weather/environmental phenomena in comparison with imagers of the previous MTSAT series [18]. In particular, the AHI infrared bands 7 (3.74-3.96 µm), 11 (8.44-8 Although a number of studies up to now have been performed exploiting Himawari-8 observations (e.g., [21][22][23][24]), only a few of them focused on volcanic ash (e.g., [25,26]). Some authors have used, for instance, a qualitative ash RGB product designed by the JMA (Japan Meteorological Agency) [27] to discriminate ash and SO2 plumes from meteorological clouds, emphasizing the advantages of using data from Himawari-8 for monitoring those features in a timely manner [25].…”

Special issue “Advancement of our knowledge on Aso volcano: current activity and background”

“…It was shown that these techniques can be effective to monitor the degassing activity of the volcanoes. Ishii et al (2018) used the Ash RGB images from Himawari-8 to detect and track SO 2 cloud from a phreatomagmatic eruption of Aso volcano on October 8, 2016. The Ash RGB is a composite image of three observation bands of Himawari-8 (RED: brightness temperature difference between 12.4 and 10.4 μm, GREEN: brightness temperature difference between 10.4 and 8.6 μm, and BLUE: 10.4 μm), and can discriminate SO 2 clouds and volcanic ash clouds from meteorological clouds.…”