Table 2. Summary of SO2 flux measurements. Uncertainties on flux measurements are asymmetrical and therefore quoted as ± [upper/lower bounds].
| Date (UTC) | Mean time (UTC) |
Measurement duration, min (number of scans) |
Mean plume speed (m s−1) |
Mean SO2 flux (tons day−1) |
± SD (1σ) |
Notes on plume condition |
| UV camera | ||||||
| 20 May 2019 | 23:30 | 120 | 9.0 ± 1.9 | 7660 ± 541/2838 | 1930 | Very clear, entire plume captured |
| 21 May 2019 | 06:20 | 160 | 5.0 ± 0.8 | 5710 ± 404/2118 | 1100 | Very clear, plume partially obscured by flank |
| 22 May 2019 | 06:22 | 44 | 16.6 ± 4.6 | 5880 ± 416/2181 | 1900 | Plume slightly covered by cloud |
| 23 May 2019 | 06:52 | 34 | 16.8 ± 5.1 | 4900 ± 346/1816 | 1100 | Plume partially covered by cloud |
| 26 May 2019 | 05:52 | 65 | 10.9 ± 5.6 | 5360 ± 379/1986 | 3180 | Plume partially covered by cloud |
| Average | 5900 ± 423/2215 | |||||
| Average (clear plume only) |
6420 ± 458/2400 | |||||
| ScanDOAS | ||||||
| 22 May 2019 | 00:23 | (43) | 1.5 ± 0.2 | 5180 ± 1966/564 | 3900 | Only plumes with complete coverage and close proximity to scanner azimuth were selected to minimize uncertainty in wind direction |
| 24 May 2019 | 00:57 | (72) | 1.8 ± 0.5 | 3770 ± 1362/360 | 1461 | |
| 26 May 2019 | 02:36 | (84) | 1.4 ± 0.3 | 4590 ± 1638/423 | 1340 | |
| 27 May 2019 | 00:58 | (30) | 3033 ± 2038/1024 | 1190 | ||
| Boat traverse (MobileDOAS) | ||||||
| 20 May 2019 | 02:43 | (30) | 3 | 4440 ± 2607/1479 | NA | |
| 20 May 2019 | 08:14 | (30) | 3 | 2590 ± 1521/868 | NA | |
| UAS traverse (MobileDOAS) | ||||||
| 26 May 2019 | 23:00 | (10) | 6 | 5200 ± 657/179 | NA | |
| Average (all DOAS) | 4115 ± 1777/814 | |||||