Contrasting the TEMPO and TROPOMI views of tropospheric NO2: Implications for diurnal variability and model evaluation

Goldberg, Daniel L., Johnson, Jeremiah, Shah, Tejas, Nawaz, Omar, Kerr, Gaige H., Chen, Lulu, Huber, Daniel and Judd, Laura 2026. Contrasting the TEMPO and TROPOMI views of tropospheric NO2: Implications for diurnal variability and model evaluation. Journal of Geophysical Research: Atmospheres 131 (14) , e2026JD046905. 10.1029/2026JD046905

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Abstract

Nitrogen dioxide (NO2) is a key indicator of unhealthy air, yet its sub-daily spatiotemporal variability has not been widely characterized across large spatial scales in North America. Tropospheric Emissions: Monitoring of Pollution (TEMPO), a geostationary hyperspectral UV-Vis instrument, offers up to 12 hourly observations per location across North America, providing opportunities to better understand NO2 sub-daily variability at wide scales. This study evaluates TEMPO tropospheric NO2 retrievals relative to TROPOspheric Monitoring Instrument (TROPOMI) and highlights the additional value of TEMPO's hourly measurements. When observations overlap, TEMPO and TROPOMI show strong spatial agreement, with some systematic differences: TEMPO NO2 is lower in unpolluted regions and marginally higher in polluted regions, primarily driven by differing air mass factor (AMF) assumptions, including surface albedo and a priori NO2 profiles. Applying a geometric AMF to both datasets substantially reduces inter-sensor differences. TEMPO reveals diurnal NO2 column patterns that broadly follow surface NO2 observations but with weaker amplitude and slower morning declines. In rural regions, TEMPO is able to monitor the NO2 diurnal patterns of wildfires, soils, and long-range transport. Comparison with a Comprehensive Air Quality Model with extensions simulation shows TEMPO reproduces much of the modeled spatiotemporal variability but highlights some systematic differences. TEMPO NO2 columns show flatter late afternoon behavior that contrasts with modeled column NO2 behavior. The simulation underpredicts urban morning NO2 and overpredicts late-day NO2, indicating potential NOx emission temporalization biases or boundary layer evolution mischaracterizations. Overall, TEMPO's diurnal data enhance our understanding of NO2 variability and provide robust constraints for air quality models and emissions assessments.

Item Type:	Article
Date Type:	Publication
Status:	Published
Schools:	Schools > Earth and Environmental Sciences
Publisher:	American Geophysical Union (AGU)
ISSN:	2169-897X
Date of First Compliant Deposit:	27 July 2026
Date of Acceptance:	6 July 2026
Last Modified:	27 Jul 2026 12:00
URI:	https://orca.cardiff.ac.uk/id/eprint/188472

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