Aerosol optical properties at Lampedusa (Central Mediterranean) ? 1. Influence of transport and identification of different aerosol types

• Main Authors: Pace, G., Di Sarra, A., Meloni, D., Piacentino, S., Chamard, P.
• Other Authors: Italian National agency for new technologies, Energy and sustainable economic development Frascati (ENEA)
• Format: Article in Journal/Newspaper
• Language: English
• Published: HAL CCSD 2005
• Subjects: [SDU.OCEAN]Sciences of the Universe [physics]/Ocean; Atmosphere; North Atlantic
• Online Access: https://hal.science/hal-00301621; https://hal.science/hal-00301621/document; https://hal.science/hal-00301621/file/acpd-5-4929-2005.pdf

International audience Aerosol optical depth and Ångström exponent were obtained from multi filter rotating shadowband radiometer (MFRSR) observations carried out at the island of Lampedusa, in the Central Mediterranean, in the period July 2001?September 2003. The average aerosol optical depth at 495.7 nm, ?, is 0.24±0.14; the average Ångström exponent, ?, is 0.86±0.63. The observed values of ? range from 0.03 to 1.13, and the values of ? vary from ?0.32 to 2.05, indicating a large variability in aerosol content and size. In cloud-free conditions, 36% of the airmasses come from Africa, 25% from Central-Eastern Europe, and 19% from Western France, Spain and the North Atlantic. In summer, 42% of the airmasses are of African origin. In almost all cases African aerosols display high values of ? and low values of ?, typical of Saharan dust (average values of ? and ? are 0.36 and 0.42, respectively). Particles originating from Central-Eastern Europe show relatively large average values of ? and ? (0.23 and 1.5, respectively), while particles from Western France, Spain and the North Atlantic show the lowest average values of ? (0.15), and relatively small values of ? (0.92). Intermediate values of ? are often connected with relatively fast changes of the airmass originating sector, suggesting the contemporary presence of different types of particles in the air column. The largest values of ? (about 2) were observed in August 2003, when large scale forest fires in Southern Europe produced consistent amounts of fine combustion particles that were transported to the Central Mediterranean by a persistent high pressure system over Central Europe. Smoke particles in some cases mix with desert dust, producing intermediate values of ?. The seasonal distribution of the meteorological patterns over the Mediterranean, the efficiency of the aerosol production mechanisms, and the variability of the particles' residence time produce a distinct seasonal cycle of aerosol optical depths and Ångström exponent values. Particles ...