18 Jul 2022
18 Jul 2022
Status: this preprint is currently under review for the journal ACP.

Validation of the TROPOMI/S5P Aerosol Layer Height using EARLINET lidars

Konstantinos Michailidis1, Maria-Elissavet Koukouli1, Dimitris Balis1, Pepijn Veefkind2,3, Martin de Graaf2, Lucia Mona4, Nikolaos Papagianopoulos4, Gesolmina Pappalardo4, Ioanna Tsikoudi5, Vassilis Amiridis5, Eleni Marinou5, Anna Gialitaki5, Rodanthi-Elissavet Mamouri6,7, Argyro Nisantzi6,7, Daniele Bortoli8,9, Maria João Costa8,9, Vanda Salgueiro8,9, Alexandros Papayannis10, Maria Mylonaki10, Lucas Alados-Arboledas11, Salvatore Romano12, Maria Rita Perrone12, and Holger Baars13 Konstantinos Michailidis et al.
  • 1Laboratory of Atmospheric Physics, Physics Department, Aristotle University of Thessaloniki, Greece
  • 2Royal Netherlands Meteorological Institute (KNMI), De Bilt, the Netherlands
  • 3University of Technology Delft (TU Delft), Delft, 2628 CN, the Netherlands
  • 4Consiglio Nazionale delle Ricerche – Istituto di Metodologie per l'Analisi Ambientale (CNR-IMAA), C. da S. Loja, Tito Scalo (PZ), Italy
  • 5IAASARS National Observatory of Athens, Athens, Greece
  • 6Department of Civil Engineering and Geomatics, Cyprus University of Technology, Limassol, Cyprus
  • 7ERATOSTHENES Center of Excellence, Limassol, Cyprus
  • 8Earth Remote Sensing Laboratory (EaRSLab), University of Évora, Évora, 7000-671, Portugal
  • 9Institute of Earth Sciences (ITC) and Department of Physics, University of Évora, Évora, 7000-671, Portugal
  • 10Laser Remote Sensing Unit, Department of Physics, National and Technical University of Athens, Zografou, 15780, Greece
  • 11Andalusian Institute for Earth System Research, Department of Applied Physics, University of Granada, Granada, 18071, Spain
  • 12Consorzio Nazionale Interuniversitario per le Scienze Fisiche della Materia and Università del Salento, Lecce, Italy
  • 13Leibniz Institute for Tropospheric Research, Leipzig, Germany

Abstract. The purpose of this study is to investigate the ability of the Sentinel-5P TROPOspheric Monitoring Instrument (TROPOMI) to derive accurate geometrical features of lofted aerosol layers on a continental scale. Comparisons with ground-based correlative measurements constitute a key component in the validation of passive satellite aerosol products. For this purpose, we use ground-based observations from quality controlled lidar stations reporting to the European Aerosol Research Lidar Network (EARLINET). An optimal methodology for validation purposes has been developed and applied using the EARLINET optical profiles and TROPOMI aerosol products, aiming at the in-depth evaluation of the TROPOMI Aerosol Layer Height (ALH) product for the period 2018 to 2021 over the Mediterranean Basin. Seven EARLINET stations across the Mediterranean were chosen, taking into consideration their proximity to the sea, which provided 34 coincident aerosol cases for the satellite retrievals. In the following, we present the first validation results for the TROPOMI/S5P ALH using the optimized EARLINET lidar products employing the automated validation chain designed for this purpose. The quantitative validation at pixels over the selected EARLINET stations illustrates that TROPOMI ALH is consistent with EARLINET, with a high correlation coefficient R=0.91 (R=0.59) and a mean bias of −1.02±0.96 km (−1.46±1.57 km) over ocean and ocean/land pixels respectively. Overall, it appears that aerosol layer altitudes retrieved from TROPOMI are systematically lower than altitudes from the lidar retrievals. This work confirms that the TROPOMI ALH product is within the required threshold accuracy and precision requirements of 1 km. Furthermore, we describe and analyse three case studies in detail, one dust and two smoke episodes, in order to illustrate the strengths and limitations of TROPOMI ALH product and demonstrate the presented validation methodology.

Konstantinos Michailidis et al.

Status: open (until 29 Aug 2022)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on acp-2022-412', Anonymous Referee #2, 21 Jul 2022 reply
  • RC2: 'Comment on acp-2022-412', Anonymous Referee #1, 08 Aug 2022 reply

Konstantinos Michailidis et al.

Konstantinos Michailidis et al.


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Short summary
Modern satellite-born sensors have the ability to derive accurate geometrical features of lofted aerosol layers on a continental scale, such as the S5P/TROPOMI instrument. Comparisons with ground-based correlative measurements constitute a key component in the validation of the more recent-in-existence satellite aerosol products. Three days with sufficient dust and smoke aerosol load over the Mediterranean are used to illustrate the performance of the TROPOMI ALH product.