The 2010 Eyjafjallajökull Eruption

Direct SO2 Plume Height Estimation
and Enhanced Ash Detection with
OMI :
The 2010 Eyjafjallajökull Eruption
Kai Yang
GEST/UMBC and GSFC/NASA
15th OMI Science Team Meeting
KMNI, 15 – 17 June 2010
Outline
Measuring volcanic plumes with OMI
Current approach and capabilities
Recent advances in retrieval techniques
Direct estimation of SO2 plume height
New aerosol index for improved ash detection
Retrievals from the Eyjafjallajökull Eruption (Iceland,
2010)
Initial volcanic plume (April 15)
Later volcanic plume (May 5)
Comparisons
Limitations and Future Improvements
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Routine and NRT OMI Processing
LF algorithm for deriving O3, SO2, and AIb
simultaneously.
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Absorber Layer Height
o
The ubiquitous ozone provides a natural scale for
measuring the height of stratified atmospheric
constituents
∂ lnITOA (N,z)
∂m
∂ lnITOA (N,z)
=
−
N
σ
= −σ a m
a
∂z
∂z
∂N
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
EISF Algorithm
Extended Iterative Spectral Fitting (EISF)
Algorithm developed for direct retrieval of SO2
plume height, in additional to O3 and SO2 column
amounts.
3
∂ lnITOA
ln Im − lnITOA = ∑
∆X p + p rrs σ rrs
∂X p
p=1
X p = X pi
2

∂ lnI
TOA
+  ∆Fc + ∑c k ( λ − λ0 ) k 

 ∂Fc
k=1
+ε
Fc =Fc i
Define new Aerosol Index : spectral slope c1
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Enhanced Aerosol Index (AIb)
TOMS AIa

 Iλ1 
 Iλ1  
AI a = −100Log10  
− Log10   

 Iλ 2 meas
 Iλ 2 calc 
(I )

λ 2 meas

⇒ −100 Log10 
 (I λ 2 )calc 
λ1 = 331 nm
λ2 = 360 nm
New AIb
The spectral slope of Lambert Equivalent Reflectivity or
MLER cloud fraction: AIb = 2700 × c1
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Enhanced Aerosol Index (AIb)
TOMS AI (AIa) vs. the new AIb:
Both AIs measure the spectral contrast after
atmospheric correction by removing the effects of
Rayleigh scattering and trace gas absorption (if any)
AIa: at the top of atmosphere (above)
AIb: at the bottom of atmosphere (surface and/or
clouds)
+ AI: presence of absorbing aerosol
− AI: absence of absorbing aerosol and the likely
presence of clouds and/or non-absorbing aerosol.
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Eyjafjallajökull Plume: April 15
SO2 Column
SO2 Height
AIb
Max SO2: 6.4 DU @ (2.46106°E, 61.5794°N)
Height: 3.7 km.
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Eyjafjallajökull Plume: May 5
SO2 Column
SO2 Height
AIb
Max SO2: 30.3 DU @ (9.33631°W, 57.7617°N)
Height: 8.2 km.
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
SO2 Emission and
Plume Height Distribution
SO2 Tonnage: 29 kt
April 15, 2010
SO2 Tonnage: 91 kt
May 5, 2010
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
SO2 Retrieval Errors
Inhomogeneous effect
Aerosol effect
Underestimate SO2 amount if using correct height
Underestimate height but reduce bias in SO2 amount if
both are derived simultaneously.
Non-absorbing aerosol: - height, + column
Absorbing aerosol at or above SO2 plume or with a large
loading:
- height, + column
Absorbing aerosol with a small loading below the SO2
plume :
+ height, - column
Ozone profile effect
Retrieval of small SO2 need accurate ozone profile
Large SO2 retrieval not sensitive to ozone profile shape
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Boundary Layer SO2
ISF SO2, OMI 03/04/2010
O3-SO2 sonde data
Dr. G. Morris (V. Univ.)
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010
Future Improvements
Simultaneous Ozone profile retrieval in conjunction with
SO2 column and layer height
Direct estimation of aerosol properties and aerosol height
from hyper-spectral BUV measurements for improved
aerosol corrections
K. Yang, GEST/UMBC & GSFC/NASA
15th OMI Science Team Meeting, KMNI, 15 – 17 June 2010