Application of MAIAC high spatial resolution aerosol retrievals over Po Valley (Italy)

The Moderate Resolution Imaging Spectroradiometer (MODIS) Aerosol Optical Depth (AOD) data retrieved at 0:55 μm with spatial resolutions of 10 km and 1 km AOD have been considered in this work. The 10 km resolution of MODIS AOD product is from the MODIS Collection 5:1 dark target retrieval and the 1 km resolution retrieval is from the new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm. We evaluate ability of these two products to characterize the spatial distribution of aerosols in urban areas through comparison with surface PM10 measurements. The Po Valley area (northern Italy) is considered in this study since urban air pollution is an important concern. Population and industrial activities are located in a large number of urban areas distributed within the valley. The 10 km spatial resolution of MODIS AOD product is considered too large for air quality studies at the urban scale. Using MAIAC data at 1 km, we examine the relationship between PM10 concentrations, AOD, and AOD normalized by Planetary Boundary Layer (PBL) depths obtained from NCEP global analysis, for year 2012 over the Po Valley. Results show that the MAIAC retrieval provides a high resolution depiction of the AOD within the Po Valley and performs nearly as well in a statistical sense as the standard MODIS retrieval during the time period considered. Results also show that normalization by the analyzed PBL depth to obtain an estimate of the mean boundary layer extinction is needed to capture the seasonal cycle of the observed PM10 over the Po Valley.