Spatial and temporal UV irradiance and aerosol variability within the area of an OMI satellite pixel
1Finnish Meteorological Institute, Climate Change Unit, Helsinki, Finland
2Laboratory of Atmospheric Physics, Aristotle University of Thessaloniki, Greece
3Finnish Meteorological Institute, Kuopio Unit, Finland
4National Observatory of Athens, Institute of Space Applications and remote sensing, Athens, Greece
5National Observatory of Athens, Institute for Environmental Research and Sustainable Development, Athens, Greece
Abstract. Results of an experimental campaign that took place in the greater Thessaloniki area were used to investigate temporal and spatial UV variability within an OMI satellite pixel. UV irradiance and aerosol optical depth measurements were performed for a one month period at three sites characterized as urban, rural and industrial, depending on their location and possible local aerosol sources. OMI showed a general UV irradiance overestimation compared to all three sites and for all atmospheric conditions. During the campaign the standard deviation calculated from the three sites for UV irradiance at 324 nm was of the order of 26%. For cloudless days with high spatial aerosol variability, UV differences reached ±20% within the OMI pixel. For cloudy days UV differences up to 100% were found at the three sites, a percentage that depends on the ground-based data integration time used for the comparison. Here we tried to focus on the limitations when trying to interpret results of UV irradiance comparisons between OMI satellite and ground based stations, taking into account the UV variability within an OMI pixel, due to such small scale spatial cloud and aerosol inhomogeneities.