Multi-Spectral/Multi-Sensor Satellite Retrievals of Ozone, Nitrogen Dioxide, and Carbon Monoxide During FIREX-AQ 2019

Satellite-based monitoring of carbon monoxide (CO), ozone (O₃), nitrogen dioxide (NO₂), and formaldehyde (CH₂O), among other constituents, is an integral part of the 2019 NOAA/NASA Fire Influence on Regional to Global Environments Experiment – Air Quality (FIREX-AQ) campaign. Key satellite sensors for FIREX-AQ are Cross-Track Infrared Sounder (CrIS; observes CO, O₃) and Ozone Mapper and Profiler Suite (OMPS; O₃, NO₂) on Suomi NPP, as well as the Sentinel 5P Tropospheric Ozone Monitoring Instrument (TROPOMI; O₃, NO₂, CH₂O, CO): CrIS and OMPS simultaneously observe ozone from the same platform but in different spectral regions (IR and UV) with different vertical sensitivities, and TROPOMI covers all major fire emission products from the UV to the near-IR with extremely high spatial resolution. However, differences in the assumptions and retrieval approach usually pose a challenge when combining and comparing retrieval products from different sensors.

At JPL we are currently developing an accurate and flexible integrated retrieval code by combining two existing projects: Reusable Framework for Atmospheric Composition (ReFRACtor), an extensible multi-instrument atmospheric composition retrieval framework that supports and facilitates data fusion of radiance measurements from different instrument in the UV, Visible, and near- to thermal IR spectrum; and Multi-Spectral, Multi-Species, Multi-Sensors (MUSES), an atmospheric composition retrieval code based on optimal estimation, which has been applied successfully to joint AIRS/OMI observations. The ReFRACtor/MUSES code is designed to retrieve trace gas vertical profile concentrations and total column amounts in a consistent manner across spectral regions, by combining fast and accurate radiative transfer code with a non-linear optimal estimation solver. Inclusion of instrument-specific information (e.g., instrument transfer functions) for a variety of sensors allows the application of the same code base to different sensors for a consistent retrieval methodology across platforms, which facilitates the comparison of retrievals of the same species across platforms. The goal is to extend the currently single-instrument retrieval capabilities to joint multi-spectral retrievals of the kind AIRS/OMI and CrIS/OMPS.

We present latest results on the concentration and vertical distribution of O₃, NO₂, and CO, derived from the application of ReFRACtor/MUSES to AIRS, OMI, CrIS, OMPS, and TROPOMI observations during 2019 FIREX-AQ. We describe the building blocks of the retrieval code, including radiative transfer approach, a priori assumptions on the atmospheric state, and the non-linear solver, and we outline the roadmap of the future development of an Open Source code base. Results from ReFRACtor/MUSES will be compared with standard data products from the individual satellite sensors.