Air pollution assessment over Po valley (Italy) using satellite data and ground station measurements

Due to their effect on human health, the study of atmospheric pollutants is an important concern in the Po valley – northern Italy – one of the main industrialized and populated areas of the country. Our work focuses on the applicability of satellite Aerosol Optical Depth (AOD) retrievals in support of air quality monitoring and assessment in urban environments within the Po valley. This has been accomplished by using the implementation of the International MODIS/AIRS Processing Package (IMAPP) Air Quality Applications software, IDEA-I (Infusing satellite Data into Environmental Applications-International) over the Po valley study area. IDEA-I is a globally configurable software package that uses either Terra or Aqua MODerate resolution Imaging Spectro-radiometer (MODIS) AOD product retrievals to identify local domains of high values of aerosol. For our specific analyses, IDEA-I has been used over the large European domain, centred over the Po Valley. One year (2012) of MODIS AOD product retrievals from MODIS on board NASA’s Terra (MOD04) or Aqua (MYD04) satellite has been considered using IDEA-I in a retrospective study. These retrieved data have been also compared with the Particulate Matter (PM 10 ) measurements from the Italian Agency for Environmental Protection (ARPA) ground-based network stations. The acceptable results obtained by the correlation PM 10 – AOD suggest the satellite AOD as a good substitute for monitoring air quality over the Po valley domain. Yet the 10 km resolution of MODIS – AOD product is considered too large for air quality studies at urban scale. Recently, a new Multi-Angle Implementation of Atmospheric Correction (MAIAC) algorithm has been developed for MODIS which provides AOD data at 1 km of spatial resolution. We have evaluated ability of MODIS product MOD04 and MAIAC products to characterize the spatial distribution of aerosols in the urban area through comparison with surface PM 10 measurements. Using MAIAC data at 1 km, we have examined the relationship between PM 10 concentrations, AOD, and AOD normalized by Planetary Boundary Layer (PBL) depths obtained from NOAA National Center for Environmental Prediction (NCEP) Global Data Assimilation System (GDAS), for the same period of analysis. 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 highlight 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 PM 10 over the Po Valley.