This image shows the residual difference between SCIAMACHY observations and TM3 results. The results are displayed in parts per billion by volume (ppbv), ranging in most pixels from -20 to 20 ppbv (+/- 1% relative difference).
The largest discrepancies can be seen over tropical broadleaf evergreen forests in South America, central Africa and Indonesia. In these areas, measured values are persistently high than predicted by the model. Prevailing wind directions cause transport of these discrepant concentrations over the oceans (e.g northwest of South America or west of Africa).
Column-averaged methane volume mixing ratio (VMR) in parts per billion results were gathered from the TM3 model for the time period of August through November 2003. Only modelled values that are colocated in space and time with the respective SCIAMACHY measurements are used for the averaging.