POTENTIAL USE OF IASI FOR VOLCANIC CLOUDS
DETECTION AND MONITORING
Thierry PHULPIN, Michael DANA
CNES, Toulouse, FRANCE
NEEDS
OBJECTIVES
•CLIMATE : Impact of SO2
and Stratospheric aerosols on
climate.
Mapping of sulfur dixoyde or
aerosol, Mass loadings,
conversion SO2 to H2SO4,
transport, depositioo,
Radiative properties.
VOLCANIC CLOUD
•AERIAL SAFETY
Identification of ash, amount,
The danger resulting from
altitude, transport
volcanic explosion has justified
the opening by OACI of 9
Volcanic Ash Activity Centers
(VAAC) in charge of
monitoring and alert
•Volcanic eruption releases gases (H2O, SO2,
HCl etc.) and aerosols (ash, sulfates)
•Processes are relatively well known and
documented
•Composition is highly variable.
•Particle size varies with time
•Several stages of development during the
first hours
•Altitude, vertical extent of cloud varies
•Lifetime is a function of particle size and for
SO2 of the altitude
Volcanic Cloud Stages
Volcanic Cloud stage
1
2
3
Duration, hrs after eruption stops
A s h f a l lout, km from volcano
Area of ash fallout, km 2
A s h f a l lo u t d iameter range, mm
A s h f a l lout rate, kilotonnes/hr
Fraction of fine ash(d= 1-25 µm), %
C loud Area, km 2
C lo u d A r e a c h a n g e , % / h r
M e a n O p t ical Depth, 11 µm
C lo u d a s h b u r d e n , t o n n e s / k m 2
~1-2
<25
<300
>0.5
>10 4
<1
<10 4
>100
>2
>25
18-24
25-400
~5 x10 4
0.5-<0.01
<10 4 -10 2
10-50
10 4 -10 6
30-50
0.5-2
3-10
24-96+
>400
?,discontinuous
<0.01
" v e ry l o w "
>50
10 6 ,decreasing
-10 to +10
<0.3
<3
Fraction of ash mass suspended, %
100-~30
~30-3
<3
Rose et al, J Geology, in press
SATELLITE
MONITORING
Environmental factors that weaken
or obliterate the negative 4-5 BTD
signal
Current status
Satellite is the unique tool
Data Used :
GOES, AVHRR, TOMS,
HIRS
SEVIRI, SCHIAMACHY,
AIRS
•Single Channel method : Visible or infrared radiance --> Poor but easy
•Two-channel : GOES, AVHRR (e.g. Shneider, Rose) --> Generally efficient
•TOMS: Aerosol Index and SO2 column (Bluth, 2001)--->Good supplement
but no real time
•Multichannel : HIRS (Prata), MODIS (Yu and Rose), --->Good
SEVIRI (Watkin)
•AIRS (L. Strow, F. Prata)
---> Added value
•IASI ????
1. Early Opacity of plume (blocks transmission)
--very cold BT and dramatic buildup
2. Atmospheric water vapor in first 3 km (tropics)
--clear pixel 4-5 BTD values of +3
3. Cold Background under volcanic cloud (rare)
--low B4 BT around cloud
4. Presence of ice in the volcanic cloud
--volcanic source, dynamics
BRIGHTNESS TEMPERATURE
TRANSMITTANCE
SO2 Transmittance to ground in B3
WHAT IASI COULD BRING ?
1
Effet SO2 (∆Tb ) à 1150 et 1350cm-1
0,95
0
240
12
8
250
6
240
230
4
220
230
1
225
220
215
210
205
SO2 stdt
0,9
SO2*10000
SO2 *10000 9
HIRS 10000 8
0,8
200
wavenumber (cm-1)
0,7
0,6
0,5
2
210
0,4
3 absorption bands but
mixed with other gases
801
1001
601
201
401
0
1
200
Pressure (hPa)
•Simulation for HIRS 3
(NOAA 16), AIRS, IASI
0,3
0,2
SO2Ground
SO2_gazx1
SO2_gazx2
NoSO2(x1)
0,1
0
1120
1121
1122
1123
1124
1125
1126
1127
1128
1129
1130
1131
1132
1133
1134
1135
1136
1137
1138
1139
1140
1141
1142
1143
1144
1145
1146
1147
1148
1149
1150
1151
1152
1153
1154
1155
1156
1157
1158
1159
1160
1161
1162
1163
1164
1165
1166
1167
1168
1169
1170
1,0E-04
SO2 Transmittance
Wavenumber in B2
1,0E-05
•Profiles P,T,U from Raob
Tunis 28/09/02 0Z
Other gas absorption.
Série1
Série2
1,0E-06
1
Série3
Série7
At 1150 cm-1:
Série8
Série10
290
280
no SO2 level 24
300
400
500
600
700
800
900
1380
1370
1360
1350
1340
1330
1320
1310
1300
1290
1280
1270
1260
1250
1240
1230
1220
1210
1200
1190
1180
1367 T
1370 T
1000
HIRS 12 T
220
210
200
0,00E+00
5,00E+02
1,00E+03
1,50E+03
2,00E+03
2,50E+03
3,00E+03
Ecarts avec profil 6
0,5
320
5
320
315
310
310
2,5
0
305
0,3
300
300
SO2 *1000
295
Pression (hPa)
0
-0,5
290
SO2 500 8 et 9
SO2 *1000 9
285
SO2 *250 500 250
290
-2,5
-1
280
0,2
From Coheur et al, 2003
Much stronger at 1350 cm-1
240
0,4
1,0E-10
200
HIRS ch 12
1166,5 T
1168 T
230
0,5
CH4, H2O, N2O
100
1367
1370
250
0,6
At 1350 cm-1:
1,0E-09
0
1166,5
1168
270
260
CFC12, N2O
1,0E-08
Sensitivity to level and
distribution of SO2
300
noSO2
SO2 gazx1 level 24
0,7
Série9
Transmittance
densité SO2
0,8
Série6
Tb =f (colonne SO2)
SO2gazx1
Série5
1,0E-07
1170
SO2seul
0,9
Série4
• 10 profiles SO2 around 8
km for sensitivity study
USING HIGH SPECTRAL RESOLUTION OF IASI
AND AIRS WILL REDUCE INFLUENCE OF OTHER
GASES AND IMPROVE DETECTION AND TOTAL
AMOUNT
.
• SENSITIVITY IN B2 > B1 > B3 But SATURATION
FOR HIGH CONTENT AND LINE MIXING
CHANNELS GOOD FOR SPECTROSCOPY :
B2: For low amounts : 1344, 1345.5. Possibly 1366.5
and 1370.5
B1 : For mean amounts : 1132.75, 1139.75, 1141.5,
1147, 1163.25 + 1129.25, 1143.75, 1156
B3 :For very large amounts :2499, 2508,2509, 2510
Problem : Influence on Tb of Level where SO2 is
concentrated
•
Wavenumber
SO2 Transmittance to the ground in B1
235
650
700
750
800
850
900
950
1000
1050
1100
1150
1200
1250
1300
1350
1400
1450
1500
1550
1600
1650
1700
1750
1800
1850
1900
1950
2000
2050
2100
2150
2200
2250
2300
2350
2400
2450
2500
2550
2600
2650
2700
2750
Température(K)
260
Mixing ratio et E06*MR SO2
10
270
Transmittance
Température28/10/02OZ
Humidité 28/10/02
SO2 5
280
•4A (version 4AOP)
Includes continuum
(CKD2.0), H2O, CO2, N2O,
CO, CH4, SO2, HNO3,
CFCs.
SO2*5E04
2480
2481
2482
2483
2484
2485
2486
2487
2488
2489
2490
2491
2492
2493
2494
2495
2496
2497
2498
2499
2500
2501
2502
2503
2504
2505
2506
2507
2508
2509
2510
2511
2512
2513
2514
2515
2516
2517
2518
2519
2520
245
290
SO2 *100
SO2 *1000
SO2 *5000
SO2*E04
wavenumber (cm-1)
0,75
280
-5
275
Tb (K)
Modelling Radiances
250
14
SO2 *10
1160
Tb (K)
300
-34
-36
-38
-46
-48
-50
NoSO2 (x1)
255
-30
-32
1400
SO2+gaz*1
SO2+gaz2*
1150
0,8
1140
265
260
-24
-26
-28
-40
-42
-44
SO2seulB3
1130
SO2 only
270
1390
0,85
275
1120
285
-18
-20
-22
1110
290
280
•Fourier transform spectrometer on
Metop
=>15 years of high quality data
•Spectral range: 2760 to 645 cm-1
•Spectral resolution: 0.35 to 0.5 cm-1
•Radiometric performances
•Spatial sampling
0,9
-6
-8
-10
-12
-14
-16
1100
SIMULATIONS
Transmittance
IASI
300
295
Brightness temperature Tb (K)
-2
-4
IASI 1c Standard et *10000
-1,5 270
270
-7,5
265
260
260
0,1
-2
255
-10
250
250
-2,5
245
-12,5
SO2 *E04
240
240
Delta 8-9 5000 5000
235
-3
0
230
delta 9 10000
230
-15
delta 10 2500 5000 2500
1500
1480
1460
1440
1420
1400
1380
1360
1340
1320
1300
1280
1260
1240
1220
1200
1180
1160
1140
1120
1100
1080
1060
1040
1500
1480
1460
1440
1420
1400
1380
1360
1340
1320
1300
1280
1260
1240
1220
1200
1180
1160
1140
1120
1100
1080
1060
1040
1020
1000
-17,5
1020
-3,5 220
1000
1340
1341
1342
1343
1344
1345
1346
1347
1348
1349
1350
1351
1352
1353
1354
1355
1356
1357
1358
1359
1360
1361
1362
1363
1364
1365
1366
1367
1368
1369
1370
1371
1372
1373
1374
1375
1376
1377
1378
1379
1380
225
220
Wavenumber (cm-1)
Wavenumber
AEROSOLS
255
250
z1
245
36
48
•Density at maximum concentration : 10 cm -3 to 50 cm -3
(15 months after eruption (SAGE II)
•Distribution : Lognormal, monomodal (background) but
bimodal in case of eruption
•Optical thickness : from 0.015 to 0.086 (or More)
•Optical thickness : from 1 to less than 0.1
Wells Bay Alaska
August 1992 Spurr
Mastersizer
Ash Cloud Area
SO2 Cloud Area
Optical depth
4
240
1000000
10
100000
1
230
Cloud area,
km2
Volcanic Ashfall from
Crater Peak Eruption
3.5
Collected by R G
McGimsey,,
McGimsey
USGS/AVO
3
Optical
Depth, 10.8
microns
10000
0.1
2.5
1000
1600
1800
2000
2200
2400
2600
0.01
0
2800
50
100
150
200
Wavenumber (cm-1)
=> Sensitivity study must account for different distribution,
density, efficient radii
0
0.1
Hours since eruption
1
10
100
1000
Diameter, microns
800
850
900
950
1000 1050 1100
1220,00
1215,00
1210,00
1205,00
1200,00
1195,00
1190,00
1185,00
1180,00
1175,00
1220
1195
1170
1145
1120
995
1095
970
1070
1045
945
1020
920
895
870
845
820
220
TB -15
215
273,00
1150 1200 1250 1300 1350 1400
1450
1500
750
strow2
900
950
1000
1050
1100
1150
1200
1250
2760
2735
2520,00
2515,00
2510,00
2505,00
2500,00
2495,00
2490,00
2485,00
2480,00
2475,00
2470,00
2465,00
2460,00
2455,00
2450,00
2445,00
2440,00
2435,00
2710
2685
2660
2635
2610
2585
2560
2535
2510
2485
268,00
2430,00
Wavenumber (cm-1)
2460
2435
190
2410
•to retrieve Total amount SO2 and altitude of maximum.
•Optical thickness of ash aerosol and efficient radius
850
200
195
2110
Tbatm13noaero
Tb aero Ext FSS
800
TB -15
K
205
2085
•A priori first results (consolidated by AIRS results) show that with
IASI it is possible
•to discriminate SO2, water, Ash and SO4 aerosols.
272
=> can be neglected to simulated
aerosol with 4A in [800-1000] 270
and [1100-1240]
Mod3/mod1
Mod2/Mod1
Mod8/Mod1 trop
Mod8/mod1 SubW
0,90
750
274
2425,00
0,92
795
IASI
230
225
2060
=> Effect cannot be simply
added (better coupling needed)
Mod8/mod1
Mod7/mod1
mod6/Mod1
mod5/mod1
Mod4/mod1
0,94
770
745
720
695
278,00
airsband5
235
210
Small lines slightly visible even276
in the continuous part.
0,96
1367
100,00
278
245
240
1960
colonne SO2 (dobson)
Ratio smoother than difference
airsband1
IASI
250
2385
Wavenumber
• No possibility to vary independently the various parameters :
distribution n(r), mean radius and variance, efficient radius,
density N(z).
•Study needs to be complemented with a High Spectral resolution
RTM including multiple scattering.
But for same aerosol function of280
atmosphere
260
255
2360
1550
283,00
265
2335
1450
282
2310
1350
275
2285
1250
0,98
1370
strow1
288,00
2260
Ratio or difference are a
function of aerosol type.
1,00
1166,5
1170
TB -15 K
215,00
270
Brightness temperature (K)
Série1
-1,50E-02
1,02
150,00
• spectral resolution (2cm-1) not sufficient to resolve interactions
between scattering and gaseous absorption lines
284
350,00
200,00
• MODTRAN (+DISORT) not suited since
Tb (K)
L(4A) -L(Modtran)
-5,00E-03
1150
220,00
280
Conclusions
286
-1,00E-02
1050
225,00
290
288
950
230,00
285
290
Modtran at 1cm-1 close
to 4A (degraded)
850
IASI
wavenumber (cm-1)
simul 4A & Modtran
0,00E+00
750
235,00
airsband5
TB -15 K
2235
1400
240,00
2210
1200
235
230
225
220
215
210
2185
1000
245,00
2160
800
IASI
250,00
2135
220
600
airsband1
255,00
200
195
190
Large variability
1
0.5
260,00
205
Data still missing to characterize these aerosols
2
1.5
265,00
1400,00
24
Time (hours)
1395,00
12
260
255
250
245
240
1390,00
0
270,00
270
265
1385,00
•Particle size : Typically 0.1 µm (background), 0.5-1 µm
(eruption)
0
250
•Time of residence: several months
•Altitude: stratosphere
1380,00
50 Micron
20,000
10,000
1375,00
1.0 Micron
5.0 Micron
10 Micron
40,000
30,000
1370,00
260
•Distribution : Bimodal, but generally
lognormal used
Theoretical Particle Fall
50,000
275,00
1365,00
•Altitude: up to 20 km
•Particle size : from 500 µm to 5 µm
280,00
(cm-1)
IASIwavenumber
Band 2 : 1200-2040
cm1
1320,00
•Time of residence: until 200 hours or more
270
290
285
280
275
•Originated from atmospheric sulfur gases oxydation
•Nature : H2SO4 (75% on average) + water (25%)
•Nature : andesite, silicates
280
670
What we know about sulfate aerosol
Brightness Temperature (K)
290
650
1160,5
1163,5
TB -15
248,00
195
645
What we know about volcanic Ash aerosol (Rose et al, J Geology, 2002)
-3,00E-02
1139,5
253,00
200
1170,00
1250
1165,00
1200
1360,00
1150
1160,00
1100
1355,00
1050
1155,00
1000
1350,00
950
1150,00
900
1145,00
850
1200
1225
1250
1275
1300
1325
1350
1375
1400
1425
1450
1475
1500
1525
1550
1575
1600
1625
1650
1675
1700
1725
1750
1775
1800
1825
1850
1875
1900
1925
1950
1975
2000
2025
4
-2,00E-02
DTB 1132,5
1136
IASI BAND1 645-1240 cm-1
190
2
16
-2,50E-02
250,00
258,00
215
1140,00
800
Comparaison 4A/Modtran
300,00
IASI
220
1345,00
240
Wavenumber (cm-1)
2F
8
1,00E-02
400,00
263,00
230
225
205
750
5,00E-03
450,00
Série1
airsband5
235
210
IVULCN 1
2
3
4
5
6
7
8
τ0.55 0.00688 0.0271 0.0946 0.0946 0.0271 0.0271 0.0946 0.274
1,50E-02
500,00
268,00
1340,00
8
∫ s ( z ). dz
245
240
1335,00
3
z2
airsband1
IASI
273,00
TB -15 K
1135,00
5
τ 0 .55 =
260
-
250
1330,00
-
avec
4
278,00
255
1130,00
z1
283,00
265
260
1125,00
z2
z1
-
265
1120,00
z2
z1
288,00
1325,00
FRESH
VOLCANIC
z2
τλ(z1, z2) = ∫βext(z,λ).dz= ∫kext(λ).s(z).dz=kext(λ)∫s(z).dz
275
EXTREME
VOLCANIC
7
2
285
275
270
HIGH
VOLCANIC
6
280
Brightness temperature (K)
-
IASI versus AIRS
ivulcn8
270
Tb (K)
AGED
VOLCANIC
ivulcn7
2035
•
1
ivulcn6
2010
•
BACKGROUND
STRATOSPHERIC
ivulcn5
1985
•
βext(z, λ) = s(z) ×kext(λ)
ivulcn4
280
DISTRIBUTIONVERTICALE
BACKGROUND MODERATE
STRATOSPHERIC VOLCANIC
Altitude (Feet)
Use channels at 1150, 1350, 2500
Use microwindow at 1210 cm-1
Maps of ∆Tb= Tbi-T1210 (i=1132.75, 1139.75,
1141.5, 1147, 1163.25 + 1129.25, 1143.75,
1156 and 1344.5, 1345, 1370.5).
Detect SO2 (∆Tb > S) and evaluate if amount is
High, Mean or Low.
Best estimate with different methods :
–
Local Differential absorption
–
Contrast with clear pixels
–
Differential absorption with
microwindow.
Then, with the retrieved column and the
retrieved temperature profile, simulate radiance
at 1350 with different SO2 levels. Select by
minimization.
ivulcn3
290
• aerosols only defined by a vertical distribution
and spectral extinction
• optical properties linked to refractive index
MODELE D’EXTINCTION
cm-1.
ivulcn2
285
Aerosols in Modtran
Tb (K)
•
•
•
ivulcn1
Aerosols. Types, distribution et data
• 2 types :
– Sulfates (H2SO4) : Background et Ash (Andesite)
• Data :
– OPAC
– GADS
– Modtran : 8*2 models
• Models :
Current version of 4A does not include scattering
Modtran + Disort adequate but
Not possible to have a complete parametric study (Various refractive indices m,
distribution laws or efficient radii).
2420,00
SO2 DETECTION AND
CHARACTERIZATION WITH
IASI
•Optical thickness of ash aerosol and efficient radius
wavenumber
strow3
50,00
Ecarts Aero/noaero
Having a better resolution than AIRS and a better spectral
coverage of SO2 bands IASI is very promising for
Volcanic activity and climate monitoring
1,00E-03
0,00
0,00E+00
30
40
50
60
-1,00E-03
DeltaTb (K)
-2,00E-03
Mod8_MOD1
Mod7-Mod1
Mod6-mod1
mod5-Mod1
Mod4-Mod1
Mod3-Mod1
Mod2-Mod1
-3,00E-03
-4,00E-03
-5,00E-03
Trop Mod8-Mod1
SubAW Mod8-Mod1
Wavenumber
1500
1450
1400
1350
1300
1250
1200
950
900
1150
850
800
1100
-7,00E-03
1050
-6,00E-03
1000
20
Delta L
10
750
0