A Case of African Dust Transport over Athens Captured by a Ceilometer

The dust transport and its reaction with atmospheric pollution are increasingly gaining scientific interest as dust is considered to play a significant role in climate-change issues nowadays. The National Observatory of Athens has recently installed a ceilometer at the premises of its Actinometric Station (ASNOA). A ceilometer operates much like a lidar, but it only gives information about the laser-pulse energy (in the near IR) backscattered by clouds and atmospheric constituents (mostly airborne particles and less by molecules) in the form of attenuated backscatter coefficient; no information is given about absorption. Nevertheless, it is a useful instrument. The ASNOA ceilometer has been used in this work to record the laser-pulse echoes (backward-transmitted laser signals) on two occasions with and without African-dust transport over Athens (19 and 4 February 2010, respectively). Two methods for estimating the aerosol optical depth (AOD) for the 2 days are applied and compared. Conclusions are drawn about the applicability of the methods. Also, information about the free-troposphere transport (FTT) type of the dust aerosols is extracted from the analysis.