Figure 4: Mean daily values of AOD at 560 nm derived from MERIS at four sites with a 260 290  spatial resolution and spatially averaged over the Athens Basin. The daily Terra/Aqua MODIS AOD550 with 10 10 k spatial resolution are also given. The concentrations are four-station averaged value at the time interval corresponding to MERIS pass time. AI values for each day are given while the vertical bars express one standard deviation from the spatially averaged MERIS AOD value.