Quantifying Reactive Nitrogen Emissions From Wildland-Urban Interface Fires: A Case Study of the 2025 Los Angeles Fires

September 24, 2026

Joshua Laughner

Hosted by Dien Wu

Abstract

Wildland-urban interface (WUI) fires increasingly expose populations to air pollution; the January 2025 Eaton and Palisades fires killed 31 people and destroyed over 16,000 Los Angeles structures. NO2:CO enhancement ratios (ERs) are the standard satellite metric linking fire emissions to intensity. From the operational TROPOMI products used by default, ERs on 8 and 9 January were 4.5 ± 2.8 and 8.9 ± 5.4 mmol mol-1 (1s), more than twice the largest reported for 15 western U.S. wildfires in 2020 to 2021. We evaluated fire intensity, timing of peak intensity relative to overpass (which geostationary data show it preceded), ambient O3, aerosol, the a priori NO2 profile, and reactive nitrogen from burning structures. The interface is the confounder: a WUI fire elevates NO2 near the surface from urban pollution and aloft in the plume, departing from the assumed profile shape and inflating the retrieved column. Plume-adjusted profiles lower the ERs to 1.6 ± 2.1 and 3.4 ± 4.2 mmol mol-1, within the range of past fires treated identically; elevated reactive nitrogen from structural combustion can be neither demonstrated nor excluded. As WUI fires become more common and the constellation able to observe them grows, retrievals must be adapted to the interface, across species and instruments.

Dr. Laughner received his Ph.D. in chemistry from UC Berkeley in 2018, where he studied under Dr. Ron Cohen to develop improved NO2 retrievals for the Ozone Monitoring Instrument. He then moved to Caltech for a postdoc with Dr. Paul Wennberg, where he began working with the Total Carbon Column Observing Network (TCCON). In 2020, he was elected as the deputy algorithm co-chair for TCCON, then in 2024 rose to the full algorithm co-chair position. He continues to hold this position, where he is responsible for the development and release of updates for the TCCON retrieval algorithm and data products. Since 2021, he has been a scientist at NASA’s Jet Propulsion Laboratory, where, in addition to his work with TCCON, he is an active member of the Orbiting Carbon Observatory 2 and 3 algorithm and validation teams, as well as the Tropospheric Ozone and its Precursors from Earth System Sounding (TROPESS) algorithm team. His primary interests are in algorithm development, with the goals of improving precision and accuracy of existing products, developing novel methods to extract more information from available remote sensing data, and updating algorithms to use modern languages well-suited for performance and reliability.