Retrievals of Stratospheric and Tropospheric Nitrogen Dioxide (NO2) Columns from Satellite Ultraviolet and Visible Spectral Observations

Accurate retrieval of tropospheric NO₂ columns relies on precise knowledge of stratospheric NO₂ columns, which can be derived from chemical transport models (CTMs) or estimated through interpolation from regions with minimal tropospheric NO₂ contributions. However, both approaches have their limitations: stratospheric NO₂ fields from CTMs and satellite retrievals often contain biases, and small-scale spatial variations in stratospheric NO₂ can diminish the accuracy of interpolated estimates. These deficiencies can result in significant errors in stratosphere-troposphere separation (STS). In this presentation, we introduce a novel STS approach that combines retrievals from both UV and visible spectra. By leveraging the differing sensitivities of UV and visible wavelengths to tropospheric NO₂, our method provides a more accurate determination of stratospheric and tropospheric NO₂ columns. We will demonstrate the effectiveness of this technique using observations from TROPOMI, GEMS, and TEMPO, showcasing its potential to enhance the accuracy of STS in satellite-based NO₂ retrievals.