AT2 Product Report: Methane (CH4)

So far, there are methane retrievals from two satellite sensors, viz. SCIAMACHY onboard ENVISAT and IASI onboard METOP. Several scientific groups are working on the retrieval and made considerable progress in the past year. First scientific results are now available in literature and it can be concluded that SCIAMACHY firstly enables the detection of near-surface methane enhancements due to regional emissions. The details of the individual working groups (IUP Bremen, SRON, IUP Heidelberg and Service d'Aeronomie/CNRS), their data product and publications are given below.

 CH4 columns from SCIAMACHY retrieved by University of Bremen

PI

Michael Buchwitz

Type of product

CH4 vertical column in [molecules/cm2]

and CH4 column averaged mixing ratio XCH4 in [ppbv]

Instrument

SCIAMACHY/ENVISAT (nadir view)

 

Spatio-temporal sampling

Global (full coverage every six days

(neglecting clouds)),

all observations at typically 10:00 a.m. local time

 

Algorithm

WFM-DOAS

Institution

Institute of Environmental Physics /

Institute of Remote Sensing (IUP/IFE), University of Bremen,

Bremen, Germany

Point of contact

Michael.Buchwitz@iup.physik.uni-bremen.de

Web site

http://www.iup.physik.uni-bremen.de/sciamachy/NIR_NADIR_WFM-DOAS/

 

Main reference

Buchwitz, M., de Beek, R., Burrows, J.P., Bovensmann, H., Warneke, T., Notholt, J., Meirink, J.F., Goede, A.P.H., Bergamaschi, P., Koerner, S., Heimann, M., Mueller, J.-F., Schulz, A., Atmospheric methane and carbon dioxide from SCIAMACHY satellite data: Initial comparison with chemistry and transport models, Atmos. Chem. Phys. Discuss.,

4, 7217-7279, 2004.

Status

All consolidated SCIAMACHY Level 1 orbit files of the year 2003 have been processed with the latest versions of the retrieval algorithm (WFM-DOAS v0.4 and v0.41). Analysis is ongoing. Parts of the data have been compared with global models and groundbased FTIR. Reasonable agreement.

Estimated single pixel precison v0.4: 1-6%, v0.41: 1-4%;

Estimated accuracy v0.4: 2-15% (mostly neative bias due to "ice issue"), v0.41: 2-5% (still some time dependent bias due to ice issue)

Future work

Retrieval from channel 6 which is not affected by a

changing ice layer

  

CH4 columns from SCIAMACHY retrieved by SRON, Utrecht

PI

Annemieke Gloudemans

Type of product

CH4 vertical column in [molecules/cm2]

Instrument

SCIAMACHY/ENVISAT (nadir view)

 

Spatio-temporal sampling

Global (full coverage every six days

(neglecting clouds)),

all observations at typically 10:00 a.m. local time

 

Algorithm

IMLM

Institution

SRON National Institute for Space Research,

Utrecht, The Netherlands

Point of contact

a.gloudemans@sron.nl

Web site

http://www.sron.nl/www/

code/eos/atmos/ch4co2co/ch4co2co.php?1=1&menuID=1120

 

Main references

Gloudemans, A.M.S., Schrijver, H., Kleipool, Q., et al.,

The impact of SCIAMACHY near-infrared instrument calibration on retrieved CH4 and CO total columns, Atmos. Chem. Phys. Discuss., 2005,  accepted.

Status

All SCIAMACHY Level 1 orbit files for the period

January 2003 - February 2004 have been processed, using the

the latest retrieval algorithm version (IMLM v5.5), which

includes all instrument calibration corrections as provided

in the SRON Patched level 1 files. Analysis is ongoing.

Part of the CH4 data set has been compared to

calculations from atmospheric chemistry

transport models (TM3) and CH4 total columns

from ground-based FTIR measurements. Good agreement.

Qualitative comparisons with CH4 products from

other retrieval algorithms (e.g. WFM-DOAS and IMAP)

show good agreement.

Estimated accuracy: monthly-averaged data within ~2%,

daily data has somewhat lower accuracy.

Limitations: The present data set uses a fixed atmospheric

temperature profile.

Future work

The IMLM retrieval algorithm is currently being

updated with the implementation of ECMWF temperature profiles. 

Reprocessed data is expected around summer 2005, including more months of data than presently available. Small refinements

 

CH4 columns from SCIAMACHY retrieved by University of Heidelberg

PI

Christian Frankenberg

Type of product

CH4 vertical column in [molecules/cm2]

and CH4 column averaged mixing ratio XCH4 in [ppb]

Instrument

SCIAMACHY/ENVISAT (nadir view)

 

Spatio-temporal sampling

Global (full coverage every six days

(neglecting clouds)),

all observations at typically 10:00 a.m. local time

 

Algorithm

IMAP-DOAS

Institution

Institute of Environmental Physics, University of Heidelberg,

Heidelberg, Germany

Point of contact

christian.frankenberg@iup.uni-heidelberg.de

Web site

http://satellite.iup.uni-heidelberg.de

 

Main references

Frankenberg, C., Platt, U., and Wagner, T. (2005) Iterative maximum a posteriori (IMAP)-DOAS for retrieval of strongly absorbing trace gases: Model studies for CH4 and CO2 retrieval from near infrared spectra of SCIAMACHY onboard ENVISAT, Atmos. Chem. Phys., 5, 9-22.

Frankenberg, C., J.F. Meirink, M. van Weele, U. Platt, and T. Wagner: Assessing methane emissions from global space-borne observations, Science (Science Express 17.3.2005), 2005.

Status

All consolidated and non-consolidated SCIAMACHY Level 1 orbit files that are available in Heidelberg are processed.

This includes the complete year 2003 and 2004 until October.

The retrieval shows very good agreement with atmospheric model (standard deviation mostly below 30ppb)

Future work

Include sophisticated cloud detection algorithm

  

CH4 columns from IASI retrieved by Service d'Aeronomie/Universite Libre

 de BXL

PI

C.Clerbaux and P.F. Coheur

Type of product

CH4 vertical column in [molecules/cm2] and CH4 profiles in [mxr]

Instrument

IASI/METOP (nadir view)

 

Spatio-temporal sampling

horizontal: 25x25km (every 0.25 s)

Algorithm

SA-NN and Atmosphit

Institution

Service d'Aeronomie/CNRS, Paris, France

 and Universite Libre de Bruxelles, Belgium

Point of contact

C. Clerbaux: ccl@aero.jussieu.fr

Main references

S. Turquety, J. Hadji-Lazaro, C. Clerbaux, D. A. Hauglustaine, S. A. Clough, V. Cassé, P. Schlüssel and G. Mégie, Operational trace gas retrieval algorithm for the Infrared Atmospheric Sounding Interferometer J. Geophys. Res., 109, D21301, doi:10.1029/2004JD004821, 2004

data access

not yet

Future work

Coupling of the neural network and optimal estimation codes

 

 


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