Evolution of the aerosol extinction coefficient at 100 m above ground during an episode of Saharan dust intrusion as derived from data registered by a ceilometer in Almería (SE Spain)

In the process of characterize the attenuation of solar radiation by aerosols between the heliostats and the receiver in a central tower solar plant, it is important to know both the values of the aerosol extinction coefficient and its fluctuations in the lowest atmospheric layers. This objective, in the scope of the PRESOL project, can be achieved through the use of a ceilometer and a scattermeter, taking into account the ceilometer minimum usable height and the appropriate corrections to be made by the presence of water vapor and air molecules. The height of 100 m has been chosen because it is characteristic of the location of the receiver at the central tower plants. The developed methodology is based on combining measurements of a Vaisala CL51 ceilometer, a Biral SWS250 forward scattermeter and meteorological data, and simulations carried out with the SMARTS2 code to evaluate the contribution of the water vapor on the backscattered beam. The methodology has been applied in the case of an intense episode of Saharan dust intrusion that took place from 21nd to 27th February 2017 over large regions of the Iberian Peninsula. It has been possible to observe very high dust precipitation rates, which usually happen at night. As a verification of the type of aerosols, we have used data from the AERONET network at PSA. Results show the time evolution of the water vapor and aerosols extinction coefficients at 910 nm at 100 m height, throughout the episode.