2,2,1,1,- 1Royal Belgian Institute for Space Aeronomy (BIRA-IASB), D31 UV-Vis Observations, Brussels, Belgium (lorenzo.fabris@aeronomie.be)
- 2Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), Brussels Laboratory of the Universe (BLU-ULB), Université Libre de Bruxelles (ULB), Brussels, Belgium
Knowledge of the sulfur dioxide (SO2) layer height (LH) is crucial to improve our understanding of volcanic events, and their atmospheric and climatic impacts. It is also essential to better constrain SO2 emissions and ensure aviation safety. While SO2 vertical column density (VCD) retrievals from UV nadir satellite observations are well established for decades, accurate determination of the SO2 LH remains a major challenge. Existing spectral fitting algorithms are either time-consuming or lack precision and sensitivity, particularly for low SO2 amounts in the upper troposphere–lower stratosphere.
Here, we present a new Level-2 product of SO2 LH and VCD derived from the second UV spectral band (BD2) of the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor platform. The BD2 covers shorter UV wavelengths than the commonly used third UV band (BD3), providing stronger SO2 absorption features that enhance the sensitivity of the retrievals, despite higher noise levels. These retrievals were performed using the Look-Up Table Covariance-Based Retrieval Algorithm (LUT-COBRA, [1]), which has been further developed and optimized for computational efficiency [2]. This algorithm was applied to the complete TROPOMI BD2 dataset spanning 2018–2025.
We analyzed both global and regional SO2 variability, including specific volcanic events and degassing case studies. Compared to BD3, our approach demonstrates an improved sensitivity, precision, and accuracy, outperforming the current operational TROPOMI SO2 product. In addition, validation with IASI thermal infrared measurements shows a relatively good agreement, confirming the reliability of the results. Our BD2 SO2 product provides an unprecedented opportunity to monitor volcanic SO2 emissions and their impacts over the past eight years.
[1] Theys et al., Atmospheric Measurement Techniques, 15(16):4801–4817, 2022.
[2] Fabris et al., Atmospheric Measurement Techniques, 2025. doi: 10.5194/egusphere-2025-4026.
How to cite: Fabris, L., Theys, N., Clarisse, L., Franco, B., Vlietinck, J., Yu, H., Brenot, H., Danckaert, T., and Van Roozendael, M.: Enhanced SO2 plume height retrievals from TROPOMI band 2 using a look-up-table COBRA approach over the full 2018–2025 timeframe, EGU General Assembly 2026, Vienna, Austria, 3–8 May 2026, EGU26-9530, https://doi.org/10.5194/egusphere-egu26-9530, 2026.
