Measurement of the spectral extinction coefficient of atmospheric aerosols at ambient conditions and characterization of hygroscopic properties for different source regions (influenced by MARINE - DUST - SMOKE) with SÆMS, LIDAR und in-situ methods.

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Within the project we will measure the spectral extinction coefficient of the unaffected atmospheric aerosol at 3 wavelengths (405, 532, and 850 nm) with the newly developed portable SÆMS (Spectral Aerosol Extinction Monitoring System) in combination with a Raman lidar system. This innovative remote-sensing technique will be applied worldwide at selected regions for certain aerosol types and natural aerosol mixtures. The system will be equipped with humidity and temperature sensors to study the modification of the optical properties of the atmosphere at ambient conditions. This will be done for optimized optical paths (horizontal path length 1-3 km, 10-20 m height) in dependency on respective aerosol conditions. We will estimate the hygroscopic properties of the ambient aerosol for each site and will apply a typical aerosol-type dependent parameterization. The long-term goal is the characterization of the aerosol column (via combination of ground-based in-situ methods and remote-sensing methods) and a systematic investigation of the influence of the relative humidity on aerosol optical properties. The automated measurement of the extinction coefficient near the ground will be implemented in the continuous measurement station LACROS (Leipzig Aerosol and Cloud Remote Observations System) of TROPOS. This study plays a crucial role for climate modelling (parameterization of the radiative forcing of aerosols) and for the synergy of active remote sensing measurements (estimation of the optical properties of the atmospheric column) with measurements of microphysical properties with ground-based in-situ methods.