Averaged SCIAMACHY methane observations

SCIAMACHY measurements of column-averaged mathane volume mixing ratio (VMR) in units of parts per billion. The measurements are averged over the time period of August through November 2003 on a 1º x 1º horizontal grid. At least five (and up to 150) measurements are taken for each grid cells. Only a few observations are available over the ocean, since low ocean reflectivity substantially reduces the quality of the retrieval, leading in turn to unable measurements (standard deviation of the fit residual over 0.5%) that are discarded. Occasionally sun glint or clouds at low altitudes allow measurements over the ocean.