Differences between CH4 and CH4_C

What's the difference between CH4 data accessible on request only (or through MARS) and the CH4_C forecast data (latest three days) available on the ECMWF FTP server?

The methane data differ as follows:

  • CH4 comes from the CAMS Greenhouse Gases (GHG) analysis and forecasts and has a simplified chemistry but it is based on the assimilation of IASI and GOSAT methane observations.
  • CH4_C is a model-only product with full chemistry but no assimilation of CH4 observations . It's available from the ECMWF FTP server.
  • CH4 is the official value from CAMS and it is produced by from the Greenhouse Gases (GHG) analysis and forecasts suite: it is based on the near-real-time assimilation of IASI, GOSAT and TROPOMI satellite observations and uses a simplified chemistry with climatological OH fields.