Correlation between meteorological conditions and aerosol characteristics at an East-Mediterranean coastal site

摘要: Since May 2011 Microtops sun-photometer measurements aiming to determine the aerosol optical depth (AOD) and its spectral dependence (Angstrom exponent, α440/675) are performed routinely at experimental station of Port Said (Egypt) University (Lat.: 31.267°, Lon.: 32.26°, alt.: 21 masl). In parallel, an automated weather is used monitor surface meteorological parameters (wind speed direction, relative humidity, temperature, pressure…). This work uses first year original data (971 point measurements) with double objective determining 1) seasonal variability a site Egyptian Mediterranean coast, 2) potential correlation linking characteristics conditions. The 3-modal nature statistical distribution Angstrom exponents measured during shows that 3 main types aerosols can be distinguished. The most frequent observations (54% all cases) correspond fine particles associated largest (1.41 ± 0.23) α440/675 values. probability observing this increases in low wind conditions when air masses come either from south-west, which say densely populated Nile delta, or north, more distant European pollution sources. strongly suggests anthropogenic origin for these particles. At opposite side size-spectrum, coarse lowest mode (0.48 0.22) predominate 33% observations. them increasing spring dry strong (> 6 m/s) desert-winds become desert dust released by erosion arid surfaces. These also responsible individual monthly averaged (AOD500 = 0.50, April) depths site. Finally, adding supermicron marine component advected sources, medium winds north sector tend increase decrease dependence. Besides direct mixing component, effect occurrence least part intermediate exponent (α440/675 0.91 0.04) cases.