Preprints
https://doi.org/10.5194/egusphere-2023-2707
https://doi.org/10.5194/egusphere-2023-2707
12 Dec 2023
 | 12 Dec 2023

Pyrogenic HONO seen from space: insights from global IASI observations

Bruno Franco, Lieven Clarisse, Nicolas Theys, Juliette Hadji-Lazaro, Cathy Clerbaux, and Pierre Coheur

Abstract. Nitrous acid (HONO) is a key atmospheric component, acting as a major source of the hydroxyl radical (OH), the primary oxidant in the Earth's atmosphere. However, understanding its spatial and temporal variability remains a significant challenge. Recent TROPOMI/S5P UV-Vis measurements of fresh fire plumes shed light on the impact of global pyrogenic HONO emissions. Here, we leverage IASI/Metop's global infrared satellite measurements, complementing midday TROPOMI observations with morning and evening overpasses, to detect and retrieve pyrogenic HONO in 2007–2023. Employing a sensitive detection method, we identify HONO enhancements within concentrated fire plumes worldwide. Most detections are in the North Hemisphere mid and high latitudes, where intense wildfires and high injection heights favour HONO detection. IASI's nighttime measurements yield tenfold more HONO detections than daytime, emphasizing HONO's extended lifetime in the absence of photolysis during the night. The annual detection count increases by at least 3–4 times throughout the IASI time series, mirroring the recent surge in intense wildfires at these latitudes. Additionally, we employ a neural network-based algorithm for retrieving pyrogenic HONO total columns from IASI and compare them with TROPOMI in the same fire plumes. The results demonstrate TROPOMI's efficacy in capturing HONO enhancements in smaller fire plumes and in proximity to fire sources, while IASI's morning and evening overpasses enable HONO measurements further downwind, highlighting the survival of HONO or its secondary formation along long-range transport in smoke plumes.

Bruno Franco, Lieven Clarisse, Nicolas Theys, Juliette Hadji-Lazaro, Cathy Clerbaux, and Pierre Coheur

Status: final response (author comments only)

Comment types: AC – author | RC – referee | CC – community | EC – editor | CEC – chief editor | : Report abuse
  • RC1: 'Comment on egusphere-2023-2707', Anonymous Referee #1, 10 Jan 2024
    • AC1: 'Reply on RC1', Bruno Franco, 28 Feb 2024
  • RC2: 'Comment on egusphere-2023-2707', Anonymous Referee #2, 02 Feb 2024
    • AC2: 'Reply on RC2', Bruno Franco, 28 Feb 2024
Bruno Franco, Lieven Clarisse, Nicolas Theys, Juliette Hadji-Lazaro, Cathy Clerbaux, and Pierre Coheur

Data sets

The IASI/Metop pyrogenic HONO product B. Franco, L. Clarisse, and P. Coheur https://doi.org/10.5281/zenodo.10141825

Bruno Franco, Lieven Clarisse, Nicolas Theys, Juliette Hadji-Lazaro, Cathy Clerbaux, and Pierre Coheur

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Short summary
Using IASI global infrared measurements, we retrieve nitrous acid (HONO) in fire plumes from space. We detect large enhancements of pyrogenic HONO worldwide, especially from intense wildfires at North Hemisphere mid and high latitudes. Predominance of IASI's nighttime over daytime measurements sheds light on HONO's extended lifetime and secondary formation during long-range transport in smoke plumes. Our findings deepen the understanding of atmospheric HONO, crucial for air quality assessment.