Aerosols – Remote Sensing and Transport Modelling

Aerosols are suspensions of small liquid and solid particles present as traces in the atmosphere. They originate from natural sources (Saharan dust, other soil-derived particles lifted by wind, volcanic ash, wildfires, etc) or anthropogenic sources (all kinds of combustion processes, urban and industrial emissions). They are a significant factor in air quality and climate at local, regional and global scales, with a major impact on human life and economic activities. A precise characterization of aerosol properties, identification of their sources and the analysis of their dispersion over short- and long-range distances are key factors for the analysis and forecast of air pollution as well as for the understanding of atmospheric radiation and the climate system. The most advanced aerosol measurements are made using remote sensing techniques, based on light interaction with particles from atmosphere. Active remote sensing systems (lidars) emit light from a laser and measure the backscattered light. Passive remote sensing systems (sunphotometers) measure the scattering of light emitted by the sun. Satellites measure the solar light reflected by the Earth`s surface. The purpose of the project is to develop new methods for aerosol identification and classification based on their optical properties, using ground-based remote sensing measurements and satellite imagery data; to improve the capabilities of aerosol numerical modelling in FLEXPART, a dispersion model widely used for atmospheric research and practical applications. The new methods will improve aerosols characterization over Austria. Data from Romanian and German stations near to Austria from the European lidar network EARLINET and the global sunphotometer network AERONET, MACC products (integrating satellite data) from the European Copernicus Atmosphere Service and data from Sonnblick Observatory (Austria) will be used. The project proposes a new research approach for aerosol characterization, by integrating high resolution vertical profiles obtained from lidar measurements, extending from ground level to the free troposphere, with profiles from satellite measurements with lower resolution on altitude, but covering a larger area. Currently, Austria has no EARLINET or AERONET station. The benefits of a hypothetical lidar station in Vienna, eventually integrated in EARLINET, will be analyzed. The analysis will cover technical aspects (location, acquisition and running costs, manpower, operation, EARLINET integration) and improvements in aerosol characterization (identification, properties determination, source identification, dispersion, numerical modelling) over Austria and at the regional scale. Project host: Prof. Petra Seibert, Institute of Meteorology, University of Natural Resources and Life Sciences, Vienna.

Aerosols are suspensions of small liquid and solid particles present as traces in the atmosphere. A precise characterization of aerosol properties, identification of their sources and the analysis of their dispersion over short- and long-range distances are key factors for the analysis and forecast of air pollution as well as for the understanding of atmospheric radiation and the climate system. The most advanced aerosol measurements are made using remote sensing techniques, based on light interaction with particles from atmosphere. Active remote sensing systems (lidars) emit light from a laser and measure the back-scattered light. Passive remote sensing systems (sun-photometers) measure the scattering of light emitted by the sun. Satellites measure the solar light reflected by the Earth`s surface. The project implemented a new approach for studying atmospheric aerosols in Austria, by integrating the lidar measurements (extending from ground level to the free troposphere), with satellite measurements, in-situ measurements and atmospheric models, developing new methods and algorithms for determining of aerosols` properties, their transport and their origins, resulting in significant improvements. The advantage of these methods is that they provide near- real time estimation of transported aerosols at local and regional scale, as the air quality stations and aerosol remote sensing stations from European networks perform continuous measurements. The work was carried out using measurements of PM, SO 2 and O3 from in-situ back- ground sites of Austrian Environmental Agency and aerosol remote sensing measurements from Earlinet stations close to Austria (Germany, Romania) and from NASA and ESA satellites. The analysis revealed a complex aerosol environment, resulted from local aerosols and long- range transported aerosols. The long-range transported aerosols over Austria had their origin not only in Canadian wildforest fires and Sahara desert, as presented in previous studies. They are also coming from the industrial areas from Northwestern Africa, Eastern US and Southeastern US. The influence of volcano eruptions (Island, Italy) was also considered in the project. The aerosols events have a sizeable impact not only on the measured PM and SO2, but also on the level of tropospheric O3 measured at the Austrian air quality stations. In addition to known, expected pollution from Canada and North Africa fires, contributions to aerosols over Austria from Scandinavian fires, Siberian taiga fires and North Africa could also be identified. A general conclusion of this project was that the in-situ measurements in Austria and Central Europe are strongly influenced not only by local, anthropogenic aerosols but also by long-range transported aerosols: air pollution is a global problem, requiring global solutions. An atmospheric remote sensing center in Austria, including a lidar system, would improve the understanding of aerosol impact on climate. Besides its scientific impact, it would help the Environment Agencies for air quality assessment.