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An assessment of aerosol optical properties from remote-sensingobservations and regional chemistry–climate coupled models over Europe

pubblicazioni - Articolo

An assessment of aerosol optical properties from remote-sensingobservations and regional chemistry–climate coupled models over Europe

In questo lavoro è stata valutata l’incertezza nella stima dell’AOD (Aerosol Optical Depth) e del coefficiente di Ångström associata a diversi approcci modellistici e sperimentali (dati di remote sensing) in Europa per due differenti episodi.

Atmospheric aerosols modify the radiative budget of the Earth due to their optical, microphysical and chemical properties, and are considered one of the most uncertain climate forcing agents. In order to characterise the uncertainties associated with satellite and modelling approaches to represent aerosol optical properties, mainly aerosol optical depth (AOD) and Ångström exponent (AE), their representation by different remote-sensing sensors and regional online coupled chemistry–climate models over Europe are evaluated. This work also characterises whether the inclusion of aerosol– radiation (ARI) or/and aerosol–cloud interactions (ACI) help improve the skills of modelling outputs. Two case studies were selected within the EuMetChem COST Action ES1004 framework when important aerosol episodes in 2010 all over Europe took place: a Russian wildfire episode and a Saharan desert dust outbreak that covered most of the Mediterranean Sea.

The model data came from different regional air-quality–climate simulations performed by working group 2 of EuMetChem, which differed according to whether ARI or ACI was included or not. The remotesensing data came from three different sensors: MODIS, OMI and SeaWIFS. The evaluation used classical statistical metrics to first compare satellite data versus the groundbased instrument network (AERONET) and then to evaluate model versus the observational data (both satellite and ground-based data).Regarding the uncertainty in the satellite representation of AOD, MODIS presented the best agreement with theAERONET observations compared to other satellite AOD observations.

The differences found between remote-sensingsensors highlighted the uncertainty in the observations, which have to be taken into account when evaluating models.When modelling results were considered, a common trend for underestimating high AOD levels was observed. For theAE, models tended to underestimate its variability, except when considering a sectional approach in the aerosol representation. The modelling results showed better skills when ARICACI interactions were included; hence this improvement in the representation of AOD (above 30% in the model error) and AE (between 20 and 75 %) is important to provide a better description of aerosol–radiation–cloud interactions in regional climate models.

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