Figure 1.
Earth observing geostationary satellite platforms. (a) MSG-3 at 0° longitude (true-colour image). (b) INSAT at 82° E longitude (single band visible). (c) Himawari-8 at 140° E longitude (true-colour image). (d) GOES-17 at 137.2° W longitude (true-colour image). (e) GOES-16 at 0° longitude (true-colour image). (f) EPIC/DSCOVR at the L1 lagrange point (true-colour) also showing the far side of the moon during a transit. Data courtesy of the meteorological agencies: Eumetsat (EU), NMSC (Government of India), JMA/JAXA (Japan), NASA and NOAA (USA).
Figure 1.
Earth observing geostationary satellite platforms. (a) MSG-3 at 0° longitude (true-colour image). (b) INSAT at 82° E longitude (single band visible). (c) Himawari-8 at 140° E longitude (true-colour image). (d) GOES-17 at 137.2° W longitude (true-colour image). (e) GOES-16 at 0° longitude (true-colour image). (f) EPIC/DSCOVR at the L1 lagrange point (true-colour) also showing the far side of the moon during a transit. Data courtesy of the meteorological agencies: Eumetsat (EU), NMSC (Government of India), JMA/JAXA (Japan), NASA and NOAA (USA).
Figure 2.
Radiative transfer problem. The inset plot (top-right) shows the definitions of the angles and .
Figure 2.
Radiative transfer problem. The inset plot (top-right) shows the definitions of the angles and .
Figure 3.
Radiative transfer problem for a cloud embedded in a transparent atmosphere and viewed directly from above by a satellite-borne infrared instrument.
Figure 3.
Radiative transfer problem for a cloud embedded in a transparent atmosphere and viewed directly from above by a satellite-borne infrared instrument.
Figure 4.
Illustration of the relation between the retrieved quantities r, the effective particle radius, the optical depth and brightness temperatures. The black dots are data points. The nearly vertical lines are isolines of optical depth (green) and the curves correspond to different effective radii.
Figure 4.
Illustration of the relation between the retrieved quantities r, the effective particle radius, the optical depth and brightness temperatures. The black dots are data points. The nearly vertical lines are isolines of optical depth (green) and the curves correspond to different effective radii.
Figure 5.
Temperature difference distributions without (black dots) and with (red dots) a water vapour correction for four different volcanic clouds using AVHRR data. and are AVHRR channel 4 (11 m) and 5 (12 m) brightness temperatures and correspond to and nomenclature used here.
Figure 5.
Temperature difference distributions without (black dots) and with (red dots) a water vapour correction for four different volcanic clouds using AVHRR data. and are AVHRR channel 4 (11 m) and 5 (12 m) brightness temperatures and correspond to and nomenclature used here.
Figure 6.
SEVIRI ash mass concentrations (g m) for an eruption of Puyehue–Cordón Caulle volcano, southern Chile in June, 2011.
Figure 6.
SEVIRI ash mass concentrations (g m) for an eruption of Puyehue–Cordón Caulle volcano, southern Chile in June, 2011.
Figure 7.
Ash detection based on brightness temperature difference thresholds (). (a) = −0.5 K, (b) = −0.2 K, (c) = 0.0 K, (d) = +0.2 K, (e) = +0.5 K. (f) The variation of the number of pixels classified as ash (in %) as a function of .
Figure 7.
Ash detection based on brightness temperature difference thresholds (). (a) = −0.5 K, (b) = −0.2 K, (c) = 0.0 K, (d) = +0.2 K, (e) = +0.5 K. (f) The variation of the number of pixels classified as ash (in %) as a function of .
Figure 8.
Illustration of the information content in each of the IR MODIS channels for a volcanic cloud from the eruption of Anatahan volcano, Northern Mariana Islands in July 2003.
Figure 8.
Illustration of the information content in each of the IR MODIS channels for a volcanic cloud from the eruption of Anatahan volcano, Northern Mariana Islands in July 2003.
Figure 9.
(left-panel) Nadir AATSR brightness temperature difference (brightness temperature difference BTD = m) image. Pixels with BTD < 0 K are coloured in shades of yellow to red. Images such as these are extremely useful for assessing the spatial extent and boundaries of ash clouds, but do not provide information on altitude. (right-panel) Forward view (∼55°) obtained at the same time as the nadir view and scaled the same way. Note that the spatial extent of the ash is a little larger and the sensitivity is better, due to the more oblique view.
Figure 9.
(left-panel) Nadir AATSR brightness temperature difference (brightness temperature difference BTD = m) image. Pixels with BTD < 0 K are coloured in shades of yellow to red. Images such as these are extremely useful for assessing the spatial extent and boundaries of ash clouds, but do not provide information on altitude. (right-panel) Forward view (∼55°) obtained at the same time as the nadir view and scaled the same way. Note that the spatial extent of the ash is a little larger and the sensitivity is better, due to the more oblique view.
Figure 10.
MODIS/Aqua true-colour image acquired at 13:40 UT on 15 May 2010. Possible ash layers are indicated on the image.
Figure 10.
MODIS/Aqua true-colour image acquired at 13:40 UT on 15 May 2010. Possible ash layers are indicated on the image.
Figure 11.
Brightness temperature (11
m) vs. BTD plot for the images shown in
Figure 9. Note that for the forward view, the forward 11
m and 12
m data have been used. Pixels with BTD < 0 K are indicated in red (forward) and green (nadir).
Figure 11.
Brightness temperature (11
m) vs. BTD plot for the images shown in
Figure 9. Note that for the forward view, the forward 11
m and 12
m data have been used. Pixels with BTD < 0 K are indicated in red (forward) and green (nadir).
Figure 12.
Sea and land surface temperature radiometer (SLSTR) stereo pair for an eruption of Mt Etna, Sicily on 27 December 2018 at 09:25 UT. The images are placed so that a third image can be formed by staring at the pair and going slightly “cross-eyed”. Elevated clouds will appear to stand out from the image.
Figure 12.
Sea and land surface temperature radiometer (SLSTR) stereo pair for an eruption of Mt Etna, Sicily on 27 December 2018 at 09:25 UT. The images are placed so that a third image can be formed by staring at the pair and going slightly “cross-eyed”. Elevated clouds will appear to stand out from the image.
Figure 13.
AATSR height retrieval. (a) BTD image showing location of the AATSR orbit path, ash clouds and contrails. (b) AATSR quantitative height retrieval. (c) AATSR stereo pair using the 1.6 m channels. (d) Caliop validation data and AIRS ash detection showing the approximate path of the Caliop sub-satellite point. (e) FLEXPART modelling for the same ash cloud. (f) Location of the north Atlantic tracks (NAT). These are typically at altitudes of 29,000–41,000 ft (∼8.8–12.5 km).
Figure 13.
AATSR height retrieval. (a) BTD image showing location of the AATSR orbit path, ash clouds and contrails. (b) AATSR quantitative height retrieval. (c) AATSR stereo pair using the 1.6 m channels. (d) Caliop validation data and AIRS ash detection showing the approximate path of the Caliop sub-satellite point. (e) FLEXPART modelling for the same ash cloud. (f) Location of the north Atlantic tracks (NAT). These are typically at altitudes of 29,000–41,000 ft (∼8.8–12.5 km).
Figure 14.
Brightness temperature image at 11 m. The scale ranges from 230 K (white) to 300 K (black).
Figure 14.
Brightness temperature image at 11 m. The scale ranges from 230 K (white) to 300 K (black).
Figure 15.
Brightness temperature image at 12 m. The scale ranges from 230 K (white) to 300 K (black).
Figure 15.
Brightness temperature image at 12 m. The scale ranges from 230 K (white) to 300 K (black).
Figure 16.
Brightness temperature difference image at 11–12 m. The scale ranges from −3 K (black) to 3 K (white). Ash clouds appear black in these images.
Figure 16.
Brightness temperature difference image at 11–12 m. The scale ranges from −3 K (black) to 3 K (white). Ash clouds appear black in these images.
Figure 17.
Cloud identification scheme (CID) image with colours identifying which tests have been flagged for each pixel. Pixels coloured red are ones that are finally identified as containing ash. Note that some pixels over the land are wrongly identified as ash. The colour legend may be found in
Figure 18.
Figure 17.
Cloud identification scheme (CID) image with colours identifying which tests have been flagged for each pixel. Pixels coloured red are ones that are finally identified as containing ash. Note that some pixels over the land are wrongly identified as ash. The colour legend may be found in
Figure 18.
Figure 18.
Histogram of CID pixels identified by each of the tests. The percentages represent pixels identified by the test out of the total image pixels (759278). The sum of the percentages exceeds 100% because different tests are satisfied by the same pixels.
Figure 18.
Histogram of CID pixels identified by each of the tests. The percentages represent pixels identified by the test out of the total image pixels (759278). The sum of the percentages exceeds 100% because different tests are satisfied by the same pixels.
Figure 19.
Temporal development of the Sinabung eruption cloud. (a) Ash signal appears as a ring around an opaque centre. (b) Ash cloud grows. (c) Ice appears on the eastern edge of the eruption cloud. (d) Ice-rich and ash-rich portions separate. (e) Trajectories of the most negative (ash) and most positive (ice) brightness temperature pixels at different times. (f) HYSPLIT dispersion model trajectories for emissions starting at three different altitudes.
Figure 19.
Temporal development of the Sinabung eruption cloud. (a) Ash signal appears as a ring around an opaque centre. (b) Ash cloud grows. (c) Ice appears on the eastern edge of the eruption cloud. (d) Ice-rich and ash-rich portions separate. (e) Trajectories of the most negative (ash) and most positive (ice) brightness temperature pixels at different times. (f) HYSPLIT dispersion model trajectories for emissions starting at three different altitudes.
Figure 20.
Time-series of: (a) reflectance differences (2.3–1.6 m) and (b) brightness temperature differences (10.2–11.4 m), for two locations in Himawari-8 imagery for the 31 July 2015 Manam eruption. The locations were chosen to be close to the erupting column (white line and dots) and near a meteorological ice cloud (blue line and diamonds) upwind from the erupting volcano. The locations of the sites are shown in the 2.3–1.6 m difference sub-images in (a) taken at 02:00 and 04:00 UT.
Figure 20.
Time-series of: (a) reflectance differences (2.3–1.6 m) and (b) brightness temperature differences (10.2–11.4 m), for two locations in Himawari-8 imagery for the 31 July 2015 Manam eruption. The locations were chosen to be close to the erupting column (white line and dots) and near a meteorological ice cloud (blue line and diamonds) upwind from the erupting volcano. The locations of the sites are shown in the 2.3–1.6 m difference sub-images in (a) taken at 02:00 and 04:00 UT.
Figure 21.
SO total masses showing volcanic activity during 2009 as detected by the AIRS Earth Observation satellite. Note the strong emissions from Sarychev Peak lasting ∼4 weeks.
Figure 21.
SO total masses showing volcanic activity during 2009 as detected by the AIRS Earth Observation satellite. Note the strong emissions from Sarychev Peak lasting ∼4 weeks.
Figure 22.
SO total masses for 2002–2015 derived from AIRS.
Figure 22.
SO total masses for 2002–2015 derived from AIRS.
Figure 23.
AIRS SO retrieval for 16 August 2008 for two granules when strong meridional flow is drawing the SO plume southwards near to the location of the NATs.
Figure 23.
AIRS SO retrieval for 16 August 2008 for two granules when strong meridional flow is drawing the SO plume southwards near to the location of the NATs.
Figure 24.
Caliop browse image showing location of the Kasatochi plume. The black line indicates the position of the tropopause
Figure 24.
Caliop browse image showing location of the Kasatochi plume. The black line indicates the position of the tropopause
Figure 25.
Hemispheric maps of the dispersion of SO and ash, based on infrared derived indices. (a) Kasatochi SO 11 August 2008. (b) Kasatochi SO 16 August 2008. (c) Puyehue-Cordón Caulle ash 7 June 2011. (d) Puyehue–Cordón Caulle ash 11 June 2011.
Figure 25.
Hemispheric maps of the dispersion of SO and ash, based on infrared derived indices. (a) Kasatochi SO 11 August 2008. (b) Kasatochi SO 16 August 2008. (c) Puyehue-Cordón Caulle ash 7 June 2011. (d) Puyehue–Cordón Caulle ash 11 June 2011.
Table 1.
Non-exhaustive list of Earth obervation (EO) near polar-orbiting satellites carrying instruments useful for volcano monitoring from the 1970s to present. There are many other satellite platforms but this table contains the most commonly used. A = Ascending node; D = Descending node. See [
5] for an encyclopaedic description of satellites and systems for observing the Earth.
Table 1.
Non-exhaustive list of Earth obervation (EO) near polar-orbiting satellites carrying instruments useful for volcano monitoring from the 1970s to present. There are many other satellite platforms but this table contains the most commonly used. A = Ascending node; D = Descending node. See [
5] for an encyclopaedic description of satellites and systems for observing the Earth.
Satellite | Local Equatorial | Inclination | Height | Period | Repeat Cycle |
---|
Crossing Time | (Degrees) | (km) | (Minutes) | (Days) |
---|
Landsat-5 | 09:45 | 98.2 | 704 | 99 | 16 |
Landsat-7 | 10:00 | 98.2 | 705 | 99 | 16 |
Landsat-8 | 10:30 | 98.2 | 701–703 | 98.8 | 16 |
NOAA-11 | 13:40(A) | 98.9 | 845–863 | 102.1 | 11 |
NOAA-12 | 19:30(A) | 98.7 | 806–825 | 101.3 | 11 |
NOAA-13 | Failed 11 days after launch |
NOAA-14 | 13:40(A) | 98.9 | 848–861 | 102.1 | 11 |
NOAA-15 | 16:44(A) | 98.7 | 804–818 | 101.3 | 11 |
NOAA-16 | 14:00(A) | 98.74 | 845–860 | 102.1 | 11 |
NOAA-17 | 22:00(A) | 98.52 | 800–817 | 101.1 | 11 |
NOAA-18 | 14:00(A) | 99.1 | 840–862 | 102 | 11 |
NOAA-19 | 13:34(A) | 99.1 | 840–862 | 102 | 11 |
NPP | 13:30(A) | 98.74 | 824 | 101 | 16 |
ERS-1 | 10:30(D) | 98.52 | 782–785 | 100 | 35 |
ERS-2 | 10:30(A) | 98.5 | 780 | 100 | 35 |
ENVISAT | 10:30(A) | 98.5 | 780 | 100 | 35 |
Aqua | 13:30(A) | 98.2 | 705 | 98.8 | 16 |
Terra | 10:30(D) | 98.5 | 705 | 99.0 | 16 |
Aura | 13:45(A) | 98.7 | 705 | 98.8 | 16 |
MetOP-A/B/C | 21:30 (A) | 98.7 | 817–827 | 101 | 29 |
Sentinel-2A/2B | 10:30 | 98.62 | 786 | 100.6 | 10 |
Sentinel-3A/3B | 10:00 | 98.65 | 814.5 | 100.99 | 27 |
Table 2.
Summary of the important aspects of polar (p) and geostationary (g) sensors used for SO
gas and ash measurements. Note that for some of the heritage instruments (e.g., AVHRR, along-track scanning radiometer (ATSR), ans HIRS the detailed wavelength specifications may be slightly different. The sampling time for the geostationary sensors is provided in brackets, in minutes. The period of operation is given as year of launch to month and year of decommissioning. Further details of the sensors and their platforms can be found at:
https://www.wmo-sat.info/oscar/instruments.
Table 2.
Summary of the important aspects of polar (p) and geostationary (g) sensors used for SO
gas and ash measurements. Note that for some of the heritage instruments (e.g., AVHRR, along-track scanning radiometer (ATSR), ans HIRS the detailed wavelength specifications may be slightly different. The sampling time for the geostationary sensors is provided in brackets, in minutes. The period of operation is given as year of launch to month and year of decommissioning. Further details of the sensors and their platforms can be found at:
https://www.wmo-sat.info/oscar/instruments.
Sensor | Ash Bands μm | SO Bands μm | Resolution km | Platform pol or geo | Time Period Years |
---|
AVHRR-2/3 | 3.7, 10.8, 12.0 | – | 1 | p | 1979–present |
HIRS-2/3 | 3.76–4.57, 11.11, 12.47 | 7.3, 8.2 | 26 × 42 | p | 1979-present |
MODIS | 3.75–4.5, 8.6, 11.03, 12.03 | 7.33, 8.55 | 1 | p | 2000–present |
SEVIRI | 3. 8.7, 10.8, 12.0 | 7.35, 8.7 | 2 | g (15) | 2004–present |
IMAGER/MTSAT-2 | 3.75, 10.8, 12.0 | – | 4 | g (30) | 2006–05/2016 |
AHI/HIMAWARI-8 | 3.85, 8.60, 10.4, 11.2, 12.4 | 7.35, 8.6 | 2 | g (10) | 2004–present |
ABI | 3.9, 8.5, 10.2, 11.2, 12.3 | 8.5 | 2 | g (15) | 2017–present |
AIRS | 3.74–4.61, 8.80–15.4 | 6.2–8.22 | 13.5 | p | 2002-present |
IASI | 3.62–5.00, 8.26–15.50 | 5–8.26 | 12.0 | p | 2007–present |
ASTER | 8.30, 8.65, 10.6, 11.3 | 8.30, 8.65 | 0.09 | p | 2000–present |
ATSR/ATSR-2/AATSR | 3.7, 10.85, 12.0 | – | 1 | p | 1991–03/2000 |
SLSTR | 3.74, 10.85, 12.0 | – | 1 | p | 07/2016–present |
TM/Landsat-5 | 11.45 | – | 0.12 | p | 1984–06/2013 |
ETM+/Landsat-7 | 11.45 | – | 0.06 | p | 1999–present |
TM/Landsat-8 | 10.8, 12.0 | – | 0.1 | p | 1982-11/2011 |
Table 3.
Composition of ash from some recent volcanic eruptions.
Table 3.
Composition of ash from some recent volcanic eruptions.
Volcano |
---|
Oxide | Rinjani | Agung | Cháiten | Eyjafjallajökull | Grímsvötn | Etna | Askja |
---|
SiO | 64.29 | 53.82 | 73.23 | 57.38 | 49.13 | 47.14 | 70.65 |
TiO | 0.58 | 1.06 | 0.15 | 1.52 | 2.84 | 1.76 | 0.84 |
AlO | 18.76 | 20.12 | 13.83 | 14.66 | 13.25 | 17.47 | 12.28 |
FeO | 4.41 | 8.75 | 1.60 | 10.02 | 14.87 | 11.38 | 4.35 |
FeO | 3.58 | 7.10 | – | – | – | – | – |
MnO | 0.14 | 0.18 | 0.062 | 0.243 | 0.213 | 0.171 | 0.110 |
MgO | 0.92 | 2.85 | 0.34 | 2.49 | 5.20 | 5.18 | 0.84 |
CaO | 3.00 | 8.54 | 1.51 | 4.91 | 9.63 | 9.89 | 2.56 |
NaO | 4.15 | 3.32 | 4.18 | 5.53 | 2.82 | 3.60 | 3.96 |
KO | 3.55 | 1.12 | 2.957 | 1.928 | 0.468 | 2.048 | 2.317 |
PO | 0.20 | 0.23 | 0.062 | 0.315 | 0.305 | 0.574 | 0.167 |
SO | <0.003 | 0.013 | 0.377 | 0.056 | <0.003 | 0.155 | <0.003 |
LOI | 5.26 | 2.43 | 1.33 | −0.17 | −0.42 | −0.09 | 1.02 |
Total | 100.4 | 98.64 | 99.23 | 98.84 | 98.67 | 99.18 | 99.10 |
Table 4.
As for
Table 3, composition of ash from some recent volcanic eruptions.
Table 4.
As for
Table 3, composition of ash from some recent volcanic eruptions.
Volcano |
---|
Oxide | Spurr | Redoubt | Sakurajima | Kelud | Merapi | Hudson | Copahue |
---|
SiO | 55.42 | 60.45 | 60.0 | 56.1 | 54.69 | 47.60 | 52.07 |
TiO | 0.72 | 0.56 | 0.16 | 0.18 | 0.74 | 2.19 | 1.25 |
AlO | 18.76 | 17.83 | 18.3 | 19.2 | 19.29 | 16.35 | 17.54 |
FeO | 7.99 | 6.47 | – | – | – | 11.48 | 8.28 |
FeO | – | – | 5.70 | 4.89 | 7.76 | – | – |
MnO | 0.152 | 0.145 | 0.07 | 0.14 | 0.19 | 1.96 | 1.40 |
MgO | 4.40 | 2.41 | 4.10 | 5.33 | 2.25 | 4.37 | 4.39 |
CaO | 7.55 | 6.27 | 7.41 | 11.6 | 8.12 | 8.23 | 7.09 |
NaO | 3.44 | 4.01 | 3.27 | 2.26 | 3.73 | 4.08 | 3.60 |
KO | 0.953 | 1.462 | 0.76 | 0.41 | 2.16 | 1.27 | 1.86 |
PO | 0.233 | 0.211 | – | – | 0.30 | 0.74 | 0.28 |
SO | – | – | – | – | 0.03 | – | – |
LOI | 0.51 | 0.29 | – | – | – | −0.31 | 1.15 |
Total | 100.30 | 100.12 | 99.70 | 100 | 99.28 | 97.95 | 98.91 |
Table 5.
Main features of the along-track scanning radiometer (ATSR) family of instruments. Operational dates are given as month/year. • = present; – = absent. Backward view.
Table 5.
Main features of the along-track scanning radiometer (ATSR) family of instruments. Operational dates are given as month/year. • = present; – = absent. Backward view.
Parameter | ATSR | ATSR-2 | AATSR | SLSTR |
---|
Channel (width), m | | | | |
0.55 (0.02) | • | • | • | • |
0.67 (0.02) | • | • | • | • |
0.87 (0.02) | • | • | • | • |
1.38 (0.015) | – | – | – | • |
1.61 (0.06) | – | • | • | • |
2.25 (0.05) | – | – | – | • |
3.70 (0.38) | • | • | • | • |
10.9 (0.9) | • | • | • | • |
12.0 (1.0) | • | • | • | • |
Nadir swath width (km) | 505 | 505 | 505 | 740 |
Forward swath width (km) | 512 | 512 | 512 | 1420 |
Nadir angle (centre) (°) | 0 | 0 | 0 | 0 |
Forward angle (centre (°) | 55 | 55 | 55 | 55 |
Spatial resolution (km)—SWIR/visible | 1 | 1 | 1 | 0.5 |
Spatial resolution (km)—Thermal IR | 1 | 1 | 1 | 1 |
NET @ 300 K (mK) (thermal) | <500 | <500 | <500 | <500 |
Operational dates | 7/1991–3/2000 | 4/1995–9/2011 | 3/2002–5/2012 | 2/2016–present (S3A) |
| | | | 4/2018–present (S3B) |
Table 6.
Infrared cloud tests to identify cloudy pixels in SEVIRI imagery. Test parameters and thresholds have been tuned and may need adjusting from time and time.
Table 6.
Infrared cloud tests to identify cloudy pixels in SEVIRI imagery. Test parameters and thresholds have been tuned and may need adjusting from time and time.
Test | Algorithm | Criteria | Description |
---|
0 | | =–0.8 K | BTD, reverse absorption Prata (1989b) |
1 | | = 0.0 K | Cloud test |
2 | /cos() | = −0.2 K | Zenith angle () dependent BTD |
3 | > | N = 5 and = −0.9 K (ocean) −0.3 K (land) | Spatial uniformity test |
4 | > +(t) and < | = −0.2; = 250 K | Emissivity test over land |
| >; (t) = −1 + cos(2 t/24) | = 0.988, = 0.970; t = time in hours | |
5 | > and < | = 240 K | Low uniform cloud over ocean |
6 | < and > cos() | = 200 K | Clouds at high zenith angles at night |
7 | < and > | = −0.5 K | SO/Ash test. Not used currently |
8 | < and > | = 75° | Excludes pixels beyond zenith angle |
9 | > and > | = 7 K; = 72° | High zenith cloud test |
10 | < | = −5 K | Cloud/SO test over the ocean |
11 | > | = 20 K | Water vapour/high altitude SO test |