Comparing mesoscale chemistry-transport model and remote-sensed Aerosol Optical Depth

A comparison of modeled and observed Aerosol Optical Depth (AOD) is presented. 3D Eulerian multiphase chemistry-transport model TCAM is employed for simulating AOD at mesoscale, while MODIS satellite sensor and AERONET photometer AOD are used for comparing spatial patterns and temporal time series. For the estimation of AOD from TCAM model, an external mixing approach for chemical species is considered. Furthermore, a parametrization of the effect of moisture affecting both aerosol size and composition is used. TCAM simulations for year 2004 over a domain containing Po-Valley and nearly whole Northern Italy are employed. TCAM AOD reproduces spatial patterns similar to those retrieved from MODIS, but AOD values are generally underestimated. The comparison between model AOD and values at “Venise” AERONET site shows good agreement. The analysis of the extinction coefficient reveals the dominant role of the sub micron size inorganic over the domain. The results suggest encouraging perspectives in view of satellite AOD assimilation also at the mesoscale and not only at the global and regional scale as already tested in the literature.

Research highlights
► An optical module for a multiphase mesoscale CTM (TCAM) has been developed.
► TCAM AOD has been compared to both MODIS and AERONET AOD, over Northern Italy.
► Moisture effects have been assessed.
► Results suggest perspectives for EO/nonEO AOD data assimilation at the mesoscale.