OMI Science Team Meeting 24 – 27 June 2008, FMI Iterative Retrieval of Large SO 2 from Volcanic Eruptions Kai Yang 1,3 , Nikolay Krotkov 1,3 , Arlin Krueger 2 , Simon Carn 2 Pawn K. Bhartia 3 1 GEST, UMBC, Baltimore, MD, USA 2 JCET, UMBC, Baltimore, MD, USA 3 GSFC, NASA, Greenbelt, MD, USA
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OMI Science Team Meeting 24 – 27 June 2008, FMI Iterative Retrieval of Large SO 2 from Volcanic Eruptions Kai Yang 1,3, Nikolay Krotkov 1,3, Arlin Krueger.
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OMI Science Team Meeting 24 – 27 June 2008, FMI
Iterative Retrieval of Large SO2
from Volcanic EruptionsKai Yang1,3, Nikolay Krotkov1,3,
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Detect and Quantify SO2
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
SO2 Algorithms
Retrieval Challenge:
Wide range of loadings and vertical distributions
Existing Algorithms: Band Residual Difference (BRD) method Linear Fit (LF) method
Both methods are used in making OMI NRT and operational OMSO2 products.
Improvements in addressing these two questions: How small can OMI see? How large can OMI measure?
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Profile shapes: O3 (Ω) uses V8 climatology, SO2 (Ξ) uses Gaussian specified by a central height and a width.
Initial guess: latitude based O3 guess or an adjacent pixel O3 value, no SO2, derive MLER cloud fraction (Fc) at λ=333 nm, using OMCLDRR cloud pressure.
Iterative Spectral Fitting (ISF) Method:
Combo O3 and SO2 Retrievals
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K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Sample Results:Eruption of Sierra Negra
10/22/200510/22/2005
10/23/200510/23/2005
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Sierra Negra Eruption 10/23/2005OMI Retrievals: ISF vs. LF
ISF SO2 Mass LF SO2 Mass 1740 kilotons 950 kilotons (-45%)
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Largest SO2 Pixel Value
Orange: lava flowsAqua MODIS Bands 7, 2, 1 Composite
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Ozone Consistency:Inside and Outside of the Plume
Along track plots of O3 and SO2
(Along track)
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Ozone Consistency:Inside and Outside of the Plume
Maps of O3: ISF vs. LF
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
How Good are ISF Retrievals?High SO2 Fitting Residuals
1 N-value = -2.3% Radiance
Window = 317.85–333.00 nmError = 0.58 %
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
High Precision Fitting
Medium SO2 Low SO2
Fitting Error = 0.25% Fitting Error = 0.15%
Background SO2
Fitting Error = 0.14%
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
SO2 Vertical Distribution
Assumed profile too lowImeas<Iassum at short λ
Simulated Retrievals
Assumed profile too highImeas>Iassum at short λ
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Improving Retrieval Accuracy:Adjusting SO2 Central Height
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Improving Retrieval Accuracy:Adjusting SO2 Central Height
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Comparison with AIRS SO2
SO2 central height
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Anatahan Eruption: 04/06/05 Iterative Spectral Fit Linear Fit: OMSO2 TRMDerived SO2 central height ≈ 10.5 KM Assumed Central height = 7. 5 KM
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Anatahan Eruption: 04/06/05OMI – AIRS Comparison
Iterative Spectral Fit AIRS BTΔ
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Anatahan Eruption: 04/06/05Aerosol Index
Iterative Spectral Fit OMTO3
Linear Fit, OMSO2 Terra MODIS
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Nyamuragira Eruption:11/28/06SO2 & Aerosol Index
ISF SO2 ISF AI
OMTO3 AI OMSO2 AI
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Height & Distance
Nyamuragira, DR CongoNov 28 – Dec 04, 2006SO2 Plume height ~ 7 KM
Sierra Negra, Galápagos IslandsOct 23 – Nov 01, 2005SO2 Plume height ~ 3 KM
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Height & Distance
Soufriere Hills, Montserrat, West IndiesMay 20 – June 11, 2006SO2 Plume height ~ 13 KM on May 20Distance tracked ~ 20000 KM
K. Yang, GEST UMBC & GSFC NASA
13th OMI Science Team Meeting, FMI, 24 – 27 June 2008
Summary
Operational OMSO2 products tend to underestimate SO2 column amounts, more so when they are large ( > 50 DU).
New algorithm provides more consistent ozone values inside and outside of volcanic plumes, and more precise SO2 columns. Record SO2 column retrieved.
OMI UV2 measurements contain SO2 vertical distribution info. Derived central plume heights are consistent with near simultaneous AIRS observations.
The slope of theFc-λ curve yielded from the fitting algorithm may be used as a better aerosol index.