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- ItemThe spectral aerosol extinction monitoring system (SÇMS): Setup, observational products, and comparisons(München : European Geopyhsical Union, 2014) Skupin, A.; Ansmann, A.; Engelmann, R.; Baars, H.; Müller, T.The Spectral Aerosol Extinction Monitoring System (SÇMS) is presented that allows us to continuously measure the spectral extinction coefficient of atmospheric aerosol particles along an approximately 2.7 km long optical path at 30–50 m height above ground in Leipzig (51.3° N, 12.4° E), Germany. The fully automated instrument measures the ambient aerosol extinction coefficients from 300 to 1000 nm. The main goal of (SÇMS) observations are long-term studies of the relationship between particle extinction and relative humidity from below 40% to almost 100%. The setup is presented and observations (a case study and statistical results for 2009) are discussed in terms of time series of 550 nm particle optical depth, Ångström exponent, and particle size distribution retrieved from the spectrally resolved extinction. The SǼMS measurements are compared with simultaneously performed EARLINET (European Aerosol Research Lidar Network) lidar, AERONET (Aerosol Robotic Network) sun photometer, and in situ aerosol observations of particle size distribution and related extinction coefficients on the roof of our institute. Consistency between the different measurements is found, which corroborates the quality of the SǼMS observations. Statistical results of a period of 1 yr (2009) show mode extinction values of 0.09 km−1 (SÇMS), 0.075 km−1 (AERONET), and 0.03 km−1 (in situ). Ångström exponents for this period are 0.19 (390–880 nm,(SÇMS) and 1.55 (440–870 nm, AERONET).
- ItemSpectral absorption coefficients and imaginary parts of refractive indices of Saharan dust during SAMUM-1(Milton Park : Taylor & Francis, 2017) Müller, T.; Schladitz, A.; Massling, A.; Kaaden, N.; Kandler, K.; Wiedensohler, A.During the SAMUM-1 experiment, absorption coefficients and imaginary parts of refractive indices of mineral dust particles were investigated in southern Morocco. Main absorbing constituents of airborne samples were identified to be iron oxide and soot. Spectral absorption coefficients were measured using a spectral optical absorption photometer (SOAP) in the wavelength range from 300 to 800 nm with a resolution of 50 nm. A new method that accounts for a loading-dependent correction of fibre filter based absorption photometers, was developed. The imaginary part of the refractive index was determined using Mie calculations from 350 to 800 nm. The spectral absorption coefficient allowed a separation between dust and soot absorption. A correlation analysis showed that the dust absorption coefficient is correlated (R2 up to 0.55) with the particle number concentration for particle diameters larger than 0.5 μm, whereas the coefficient of determination R2 for smaller particles is below 0.1. Refractive indices were derived for both the total aerosol and a dust aerosol that was corrected for soot absorption. Average imaginary parts of refractive indices of the entire aerosol are 7.4 × 10−3, 3.4 × 10−3 and 2.0 × 10−3 at wavelengths of 450, 550 and 650 nm. After a correction for the soot absorption, imaginary parts of refractive indices are 5.1 × 10−3, 1.6 × 10−3 and 4.5 × 10−4.