Fig. 5

a The time-averaged (10-days and monthly) SO₂ PBL mass emitted by the passive degassing of Aso volcano estimated by OMPS. b Time series of the plume height (black line, from Fig. 2) and SO₂ flux (orange point). The SO₂ flux data are measured by car traverses by JMA (http://www.data.jma.go.jp/svd/vois/data/fukuoka/rovdm/Asosan_rovdm/gas/gas.html). The error bars correspond to maximum and minimum SO₂ fluxes obtained by multiple traverses. The text “15,000 ton day⁻¹” shown in the upper part corresponds to the SO₂ flux measured on 7 October 2016. c The time-averaged (10-days and monthly) and spatial-averaged cloud fraction of the OMPS data in the volcanic region (red rectangle in Figs. 3 and 4). d Correlation plot of the 10-days averaged SO₂ PBL mass against the fourth power of the maximum plume height for the corresponding period. The plume height values are converted to those above the crater bottom (= plume height in Fig. 2 + 100 m, see text). A number on the right shoulder of each point correspond to the period number shown in Fig. 3. e Correlation plot of the 10-days averaged SO₂ PBL mass against the SO₂ flux for the corresponding period. A number on the right shoulder of each point correspond to the SO₂ flux number shown in Fig. 5b. f–i Daily map of SO₂ VCDs of f TRL on 2 October, g TRL on 6 October, h TRL on 7 October, and i TRU on 8 October 2016. The triangle and the red and blue rectangles in f–i are as same as those in Fig. 3