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

Abstract

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. MODIS satellite sensor and AERONET photometer AOD are used for comparing spatial patterns and temporal timeseries. TCAM simulations for year 2004 over a domain containing Po-Valley and nearly whole Northern Italy are employed. For the computation of AOD, a configuration of external mixing of the chemical species is considered. Furthermore, a parametrization of the effect of moisture affecting both aerosol size and composition is used. An analysis of the contributions of the granulometric classes to the extinction coefficient reveals the dominant role of the inorganic compounds of submicron size. For the analysis of spatial patterns, summer and winter case study are considered. TCAM AOD reproduces spatial patterns similar to those retrieved from space, but AOD values are generally smaller by an order of magnitude. However, accounting also for moisture, TCAM AOD significantly increases to values of the same magnitude of the observed ones. The temporal performance of model AOD is tested in correspondence of AERONET site "Venise" and some temporal structures are reproduced. 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.