VARIABILITY OF AEROSOL OPTICAL-PARAMETERS BY ADVECTIVE PROCESSES

The treatment of atmospheric aerosol in the radiation transfer modelling for remote sensing or climate research purposes requires optical characteristics like spectral extinction and phase function or derived parameters under changing weather conditions. Measurements of optical thickness and sky brightness (from Sun photometry) carried out in Germany give complete data sets to derive columnar aerosol properties (aerosol size distribution, phase function and real part of the optically equivalent refractive index) by a coupled inversion-transfer program. Thus for these optical data a monitoring program is carried out at several sites in Germany. An air mass classification of the aerosol optical data can reduce the variability within the classes, gives typical optical characteristics for different air mass conditions and allows the separation of local and temporal effects by the relation of the data to comparable weather conditions. For the classification, air mass types defined by the Berliner Wetterkarte are used. Also, the aerosol optical thicknesses and phase functions as the boundary layer extinction properties have distinct characteristics for maritime, continental and aged air masses.