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Methane from SCIAMACHY

Methane from SCIAMACHY. C. Frankenberg, U. Platt, T. Wagner. Institut für Umweltphysik, University of Heidelberg MPI Mainz, Germany SRON, The Netherlands. New SCIAMACHY CH 4 and CO 2 retrieval version. ECMWF temperature, pressure and water vapor profile as prior input for each SCIA pixel

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Methane from SCIAMACHY

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  1. Methane from SCIAMACHY C. Frankenberg, U. Platt, T. Wagner Institut für Umweltphysik, University of Heidelberg MPI Mainz, Germany SRON, The Netherlands

  2. New SCIAMACHY CH4 and CO2 retrieval version • ECMWF temperature, pressure and water vapor profile as prior input for each SCIA pixel • Gtopo30 surface elevation database to compute precise surface pressures from coarse ECMWF data • Model CH4 and CO2 as prior input (mainly to constrain stratospheric CH4 variations, retrieval still unconstrained in lowermost layer) • Slight changes in spectroscopic parameters, lab studies needed to reduce uncertainties in methane spectroscopy.

  3. SCIAMACHY CH4 2004

  4. Improvements wrt the old version Most critical error: seasonal behavior in the southern hemisphere No seasonal bias any more!

  5. Comparisons with FTIR • Ideal: Comparison of CH4/CO2 directly. Alternative: CO2 from CarbonTracker (NOAA, carbontracker.noaa.gov) model. • Time series of daily-averages (incl. daily average AKs) • Question: Which stations provide SWIR spectra? Can spectra be provided (could be used in a SCIA-like retrieval algorithm to derive CH4 and CO2)?

  6. Comparisons with Models I • We will provide CH4 and CO2 total columns as well as colocated modeled CO2 from the CarbonTracker (NOAA, carbontracker.noaa.gov) model (User can decide whether to use model CO2, constant CO2 or own CO2 model to derive the column averaged CH4 mixing ratio). • Product will be in HDF5 format (some conversion tools may be added if necessary) • Dataset includes time and coordinates of SCIA pixels as well as quality criteria (use the pixel or be rather careful!) • Timeframe for deliverable: SCIA CH4 2003-2005 dataset:parts already available, complete probably by the end of the year (awaiting reprocessed level1 data from ESA)

  7. Comparisons with Models II • Problem: As of November 2005: higher noise in methane retrievals due to defect detector pixel!--> suggestion: focus on 2003-2005 time period!! • Statistical retrieval error will be provided and more work on systematic biases carried out. • Bias seems to be far lower in the new version but can never be fully excluded, thus: Suggestion: Evaluate NOAA GMD (formerly CMDL) and SCIAMACHY data in one inversion (as done by P. Bergamaschi et al, JGR, 2007)

  8. Interaction • Details about how to proceed with the FTIR and model comparison could be done directly via mail/phone • Dataset and some explanations will be put on HYMN ftp-server (old dataset already available)

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