25 September 2007 Ångström coefficient as a tracer of the continental aerosols
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The variation of the extinction coefficient with wavelength can be presented as a power law function with a constant (related to the power factor) known as the Ångström coefficient. When the particle size distribution is dominated by small particles, usually associated with pollution, the Ångström coefficients are high; in clear conditions they are usually low. Long residence time of air masses over land and in particular the passage over large urban areas cause high concentrations of fine particles and thus high values of the Ångström coefficients. The opposite effect can be observed over water. The longer the time that the air masses spent over water the more evident is a change in the aerosol size distribution caused by the deposition of continental aerosols. As a result of this process the measured Ångström coefficient values become much smaller. Therefore this parameter is a good tracer for the concentration of aerosols originated over land. The relation between the Ångström coefficient and TOS (time over sea) is demonstrated on three data sets. The first data set includes measurements collected at the Irish Atlantic coast in 1994 and 1995, the second one, data collected within the Rough Evaporation Duct (RED) experiment that took place off Oahu, Hawaii in 2001. The third one represents data collected at the Baltic Sea during cruises in 1997and 1998.
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Jolanta Kusmierczyk-Michulec, Jolanta Kusmierczyk-Michulec, Alexander M. J. Van Eijk, Alexander M. J. Van Eijk, } "Ångström coefficient as a tracer of the continental aerosols", Proc. SPIE 6708, Atmospheric Optics: Models, Measurements, and Target-in-the-Loop Propagation, 67080P (25 September 2007); doi: 10.1117/12.732426; https://doi.org/10.1117/12.732426

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