Optical properties of mineral dust outbreaks over the northeastern Mediterranean

[1] Ground-based aerosol optical measurements were conducted within the framework of the Aerosol Robotic Network (AERONET) program at the IMS-METU site at Erdemli (36330N, 34150E) along the Turkish coast of the northeastern Mediterranean from January 2000 to June 2001. The measurements were used to identify and define predominant regional aerosol optical properties, with an emphasis on mineral dust intrusion events. Dust storms affecting the region primarily originate from the central Sahara in spring, the eastern Sahara in summer, and the Middle East/Arabian peninsula in autumn. Summer and autumn dust intrusions usually occurred at higher altitudes (above 700 hPa), whereas urban-industrial aerosols from the north over the Balkan region, Ukraine, and Anatolia were transported to the region at lower altitudes. In addition to a drastic increase in the aerosol optical thickness, in some cases up to 1.8, the dust episodes were characterized by (1) a sharp drop in the Ångstrom coefficient to values near zero, (2) a high-scattering with single-scattering albedo greater than 0.95 ± 0.03, and the real part of the refractive index around 1.5 ± 0.5, both of which acquire slightly higher values at longer wavelengths, (3) a lower absorption given by the imaginary part of th