Harmonisation of atmospheric aerosol retrievals from ground based photometers

The HARMONIA COST Action (CA21119) is an international network established to harmonize atmospheric aerosol retrievals from ground-based photometers. Initiated on October 2022, and set to conclude on October 2026, HARMONIA brings together institutions, instrument developers, scientists, and commercial end-users with the objective of improving and standardizing aerosol measurements.

Aerosols, suspended in the Earth's atmosphere, significantly impact climate, air quality, and human health. Accurate and consistent remote sensing-sun photometric measurements are crucial for understanding their effects. However, variations in instruments, calibration methods, and data processing across different networks have to be homogenized. HARMONIA aims to address these challenges by fostering collaboration and standardization among global photometric aerosol networks.

The presentation aims to provide the highlights of the first 2.5 years of HARMONIA including:​

• Results of Harmonia studies towards identification of differences in Aerosol Optical Depth (AOD) retrieval methods. Including a comprehensive analysis of discrepancies in AOD retrieval methods among major networks such as AERONET, GAWPFR and SkyNet.
• Advancements in measurement quality for solar, lunar, and stellar photometry instrumentation, calibration and post processing algorithms.
• Integration of Metrology to AOD based sun photometry: including links with the Metrology for Aerosol Optical Properties (MAPP) project aiming to link metrology results with measurement accuracy and uncertainty improvements. In addition, links with the ACTRIS Calibration of aerosol remote sensing (CARS) units and relevant achievements.
• Highlights on studies using sun photometric aerosol properties towards various disciplines such as: Solar energy applications, satellite validation and model assimilation. Also, an effort to define the requirements of different user communities on the accuracy, uncertainty and spatiotemporal resolution of aerosol measurements needed for different relevant communities.

By addressing discrepancies in measurement methods and promoting best practices, HARMONIA contributes significantly to the accuracy and reliability of aerosol data, which is essential for climate research, air quality monitoring, and related fields.

Acknowledgment: The authors acknowledge the support of the COST Action CA21119 HARMONIA (Network for harmonised monitoring of atmospheric aerosol properties), supported by the European Cooperation in Science and Technology (COST).