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Campaign-wise observations

During the EUCAARI-LONGREX campaign in May 2008 several research aircraft were deployed to measure microphysical, chemical and optical properties of atmospheric aerosol over Europe throughout the tropospheric column. Airborne measurements revealed complex partitioning of the volatile aerosol components in planetary boundary layer. Measurements revealed an increase in secondary aerosol mass as a function of altitude in the boundary layer and associated increase of aerosol direct radiative forcing. The spatial distribution of sub-micron aerosol chemical composition has been characterized based upon airborne measurements in the planetary boundary layer across Europe. Organic matter (OM) dominates over sulphate over the whole of Europe, with OM concentrations typically 1.3–2.5 times greater than that of sulphate. Ammonium nitrate dominates in North-Western Europe where the emissions of NOx and ammonia reach their maximum. Both surface and helicopter data confirm that new particles are being formed in the atmosphere, either in the planetary boundary layer or in the residual layer above the PBL. As these new particles rapidly grow towards CCN-forming sizes, the modeling of these events provides an important challenge to the aerosol community.

The results from intensive observation period show that the radiative impact of anthropogenic aerosols is likely to be severely underestimated in Europe, where ammonium nitrate and OM are major components of the sub-micron aerosol burden. Such increases in AOD and radiative forcing have major implications for regional weather and climate, particularly as semi-volatile compounds are often not included in global and regional aerosol models.

Lagrangian parcel model simulations were carried out to assess the closure among the aerosol and cloud-droplet measurements carried out on board the SAFIRE ATR-42 during the IMPACT campaign. The result of that study is hoped to help a creation of a novel parameterization of the activation process in cloud models with detailed description of microphysics. An analysis of the vertical velocity statistics demonstrate the importance of vertical velocity in the CCN-activation process.

Results from modeling of atmospheric radiation demonstrate that a detailed model of the effects of aerosols on atmospheric radiation is able to capture the observed radiative signatures at the surface with a high degree of accuracy. This suggests that an accurate modeling of the direct aerosol radiative effect in global climate models is within reach, provided that the global and regional distributions of aerosols are known.

All measurement data had to be submitted to a central database (http://ebas.nilu.no), which is shared with EUSAAR and other projects, so that the EUCAARI data became part of a large established database system containing data from multiple research campaigns and monitoring activities. Some of these data are publicly available while for others the access is restricted. Furthermore, EUCAARI supported the interpretation of EUCAARI and EUSAAR data by running a Lagrangian particle dispersion model in backward mode from all EUCAARI and EUSAAR measurement data points. Furthermore, products were made available for all EUCAARI airborne observations.