Figure 4: Main results of the 3-year climatological analysis performed within EARLINET . For each station, the number of observed event () is reported following the code reported in the legend. The altitude of column bar represents the altitude of the dust layer center of mass and the white error bar its standard deviation. AOD at 355/351 nm is reported in different colors for different ranges of values. Finally, the mean values at 355/351 nm calculated within the dust layer are reported in white followed by its standard deviation within brackets.