EARLINET: the European aerosol research lidar network

Abstract

Present knowledge concerning aerosols and their distribution patterns in the earth’s atmosphere is far from adequate to properly assess their role in changing climate and environmental conditions, both regionally and globally. Information about vertical concentrations is particularly lacking. Lidar (light detection and ranging) remote sensing is the most appropriate tool to close this observational gap, and networks that deploy this technology are fundamental to the scaled-up study of aerosol concentrations, transport, and modification.1 Established in 2000, the EuropeanAerosol Research LidarNetwork (EARLINET) currently comprises 25 stations and has as its main objective the development of a qualitatively and quantitatively significant database that details the horizontal, vertical, and temporal distribution of atmospheric aerosol over the entire continent (see Figure 1). Station observation capabilities vary. EARLINET currently includes 10 single backscatter stations and 8 stations with a UV Raman channel for independent measurements of aerosol extinction and backscatter. In addition, for retrieval of aerosol microphysical properties, 7 multiwavelength Raman stations include elastic channels at 1064, 532, and 355nm, with Raman channels at 532 and 355nm, and a depolarization channel at 532nm. Network-wide observations take place systematically on a fixed schedule. For collection of unbiased data, all stations perform measurements three fixed days per week. Lidar surveillance adheres to a regular timetable: once each week around noon when the boundary layer is usually well developed, and twice weekly at night under low background light conditions in order to perform Raman extinction measurements. Other network activities monitor special events such as Saharan dust outbreaks (see Figure 2), forest fires, photochemical smog, and volcanic eruptions. A rigorous quality assurance program applies to both instruments and evaluation algorithms,2–4 and a standardFigure 1. Stations in the European Aerosol Research Lidar Network (EARLINET).