Abstract:
Atmospheric aerosols are composed of solid and liquid particles suspended in the air. Their presence influences transfer of solar radiation through the atmosphere as well as the characteristics of clouds. Aerosols are an important climate shaping factor while also influencing individual human health and the overall wellbeing of a population. The formation and evolution of aerosols are being extensively studied. A number of techniques have been proposed to monitor their spatial and temporal variability, including in-situ measurements at the ground level and remote sensing to provide information about the vertical distribution of particles and vertically integrated properties of aerosols. The key question from both scientific and economic points of view is which measurements are crucial for reliable monitoring and suitable forecast of the variability of aerosol properties and how dense should an aerosol monitoring network be. We propose a synergistic, multi-technique approach to assess the impact of in-situ, remote sensing, and integrated measurements on hybrid retrieved profiles of atmospheric aerosol properties.

To this end, the project will utilize a holistic approach with a broad range of measurements, conducted on a sub-regional scale, combined with advanced numerical techniques to retrieve consistent properties of aerosols throughout the troposphere. The research in the project is organized around three objectives devoted to multi-instrumental observations, data analysis, data integration in numerical analysis framework, and representativeness of hybrid profiles for a broader area.

An independent approach to aerosol data integration is being developed as a Generalized Retrieval of Atmosphere and Surface Properties (GRASP) software. It is a unified software package developed to retrieve atmospheric properties from multiple sources, which include remote sensing and in-situ measurements of atmospheric radiation and optical properties. It utilizes various combinations of collocated active (LIDAR) and passive (sun-sky photometer) remote techniques with in-situ measurements of aerosol to retrieve profiles at a single measurement point. These suffer from the problem of high uncertainty of LIDAR profiles retrieved close to the instrument where high aerosol concentrations are often found. To mitigate this problem ground-based in-situ measurements may be combined with LIDAR and sun-sky photometer data within GRASP retrievals. This approach allows a significant improvement in the reliability of the retrieved profiles however the transition from ground level to full overlap range (a few hundred meters between the surface and lower boundary of LIDAR’s measurement) is still uncertain.

The gap between surface in-situ measurements and lower boundary of ground-based remote sensing will be breached with airborne, in-situ measurements from UAVs. The measurement will include atmospheric physical properties (pressure, temperature, humidity) and aerosol concentration and size distribution. The incorporation of UAV based measurements into the GRASP algorithm, planned during the project, will require adaptation of existing code as well as its further development in collaboration GRASP community and assistance of this international team. The result of this joint research will be shared on the GRASP-open webpage as a new branch of the code that will be available for other researchers. Moreover, the measured data will be analyzed and published together with the international GRASP team.

The results of this project will allow for an estimation of spatial representatives of single-point measurements, depending on the utilized equipment. In particular, the impact of additional information provided by UAV measurements on retrievals will be quantified. The multi-instrumental measurements and measurements performed in different meteorological conditions and in different locations will provide information on weather’s and local terrain’s influence on the reliability of a retrieval. In particular, the required number of measurements per station in different regions and weather regimes will be assessed. Measurement campaigns in different locations will allow to investigate the influence of the local orography on the station’s representativeness. This will help decision-makers in the development of future monitoring infrastructure.