Funding: European Space Agency Service Agreement – QA4EO/SER/SUB/30 – “Quality Assurance framework for Earth Observation: QA4EO”

Description: Under the framework of QA4EO funded by European Space Agency (ESA), the project “AOD@440nm – Improved aerosol retrievals using NO2 correction” aims to improve the retrievals of Aerosol Optical Depth (AOD) of different ground based networks (AERONET, SKYNET, PGN) and of satellite algorithms (S5P/TROPOMI). Main motivation is the improvement of aerosol optical depth (AOD) and Ångström exponent (AE) datasets based on a correction using synchronous NO2 data. Development of this method is based on the fact that currently satellite climatological NO2 values are used for correcting the AOD retrievals for NO2 related optical depth. However, NO2 has high spatiotemporal variability and, hence, these values are rarely representative of the actual atmospheric conditions. Recently developed PGN offers reliable, high measurement frequency ground-based data for NO2 column, alongside with current generation of satellites (S5P/TROPOMI) which provide a high NO2 spatial detail. These data will be used to evaluate the current uncertainty of AOD and AE retrievals and integrated procedures will be developed. Spatiotemporal AOD/NO2 characteristics using two (urban and suburban) neighbouring ground based stations (including AERONET, PGN and EUROSKYRAD related instrumentation) and satellite sensors will be analysed towards demonstrating the NO2 impact on AOD for such validation activities and ways to correct for it.

Role of APCG: APCG members lead the WP2: “Improved surface based aerosol retrievals using NO2 correction”. This WP is constituted by the development of algorithms, the assessment of the products, the estimation of uncertainties and the appliance of QA procedures.