Retrieval of tropospheric SO2 from satellite infrared radiometers:

 A contribution to ACCECT-TROPOSAT-2, Task Group 1

 Fred Prata

Norwegian Institute for Air Research
PO Box 100, N-2027 Kjeller,Norway
Tel: 63 89 81 56
Fax: 63 89 80 50

 High spectral resolution infrared measurements from AIRS (Aqua) and IASI (MetOp) are used to identify and then quantify SO2 gas in the troposphere.   Exploitation of the strong 7.3 m anti-symmetric stretch absorption feature of the SO2 molecule has resulted in quantitative total column retrievals in the UTLS, with some possibility of probing deeper into the atmosphere under dry conditions (see Figure below).  The 4.0 m and 8.6 m SO2 absorption features can be used to see boundary layer SO2, but so far no one has demonstrated the accuracy and robustness of the retrievals.  We intend to utilise AIRS and IASI measurements to design and implement quantitative infrared SO2 retrieval schemes.  In the course of the work it is also likely that other trace gases (e.g. CH4, H2S, HCl and CO) may be identified from their IR absorption spectra.  To supplement the inadequate sampling from the polar orbiting satellites, we also intend to use the broad band SEVIRI sensor on MSG to reveal dynamical features of SO2 plumes (especially from volcanic sources).  Finally, we are involved in a cross-validation proposal with UMBC, USA to compare AIRS SO2 retrievals with OMI retrievals.  The optimal combination of UV and IR retrievals will be investigated.

 Time schedule

 Tasks                                                                                     2007       2008       2009

Develop radiative transfer scheme                                                *              *

and algorithms for 4.0 m SO2 scheme

using AIRS and IASI data

Develop radiative transfer scheme

and algorithms for 8.6 m SO2 scheme for                      

IASI                                                                                           *              *

Detailed analysis of up to 5 test cases

Incorporation of SEVIRI data and

Investigation of the trade-off between

spectral resolution and temporal sampling                                      *              *

Inter-comparison with OMI UV retrievals                                     *              *


Approximate manpower and cost


Person years                                                                         0.2           0.2           0.1

Yearly cost (keuro)                                                              20            20            10


Likely funding agencies


Eumetsat, EU, NASA.



 Dr Thierry Phulpin, CNES, France
Dr Simon Carn, JCET/UMBC, USA.
Jochen Kerkmann, Eumetsat, Darmstadt, Germany





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