Vertical Profiling of Atmospheric Backscatter with a Raman-Aerosol Lidar

Abstract

Aerosols have a strong impact on the planet’s thermal balance, air quality, and a variety of atmospheric processes and phenomena. In this work we present some results from a long term lidar observation of tropospheric aerosols over the city of Sofia, Bulgaria, within the framework of the European project “EARLINET‐ASSOS.” Vertical profiles of the aerosol backscattering coefficient and range corrected lidar signals are processed and analyzed. The temporal evolution and the spatial distribution of atmospheric aerosol fields are illustrated by 2D‐colormaps in height‐time coordinates. We present here several cases of aerosol loading: transport of Saharan dust (at altitudes from 3 km to 5 km), highly situated layers (from 9 km to 15 km), and anthropogenic smog (up to 2 km). All measurements were performed by using the two aerosol spectral channels of a combined Raman‐aerosol lidar developed in the Laser Radar Lab, Institute of Electronics, Bulgarian Academy of Sciences. It is based on a Q‐switched powerful frequency‐doubled Nd:YAG laser (output pulse power: up to 1 J at 1064 nm; up to 100 mJ at 532 nm; pulse duration 15 ns FWHM; repetition rate 2 Hz). A Cassegrain telescope (35 cm diameter, 200 cm focal length) collects the backscattered radiation. The lidar receiving system is based on novel smart high sensitive photo‐receiving modules. The acquisition system provides signal registration with spatial resolution of 15 m (100 MHz 14‐bit ADC). It allows for detection, storage, and processing of large volume lidar data. Our observations are in good agreement with the forecasts of Barcelona Supercomputing Center, concerning Saharan dust transport.