Observing carbon monoxide and volatile organic compounds from Canadian wildfires in 2023 from FengYun-3E/HIRAS-II in a dawn-dusk sun-synchronous orbit

This study presents the first attempt to observe wildfire enhancements of carbon monoxide (CO) and volatile organic compounds (VOCs) around sunrise and sunset from a hyperspectral infrared sounder in a dawn-dusk sun-synchronous orbit. The 2nd generation of High Spectral Infrared Atmospheric Sounder (HIRAS-II) on board FengYun-3E (FY-3E), the world's first civilian dawn-dusk orbit meteorological satellite, provides global observations in the thermal infrared spectral range with equatorial overpass times of 5:30 am/pm local solar time (LST). The spectral observations are used to retrieve CO, formic acid (HCOOH) and peroxyacetyl nitrate (PAN) emitted from three major Canadian wildfire events from June to August 2023. Extreme enhancements of CO, HCOOH and PAN were detected in the 2023 Canadian wildfires which are unprecedented in time and spatial scales and intensity. The HIRAS-II successfully captured the strong signals of CO, HCOOH, and PAN. The averaging kernel (AK) matrix, indicative of detection vertical sensitivity, peaks mostly in the free troposphere where extensive transport typically takes place. Comparison with the Infrared Atmospheric Sounding Interferometer (IASI) and the Cross-track Infrared Sounder (CrIS) reveals that the spatial distribution patterns of the total columns extracted from HIRAS-II are in good agreement. Validation with the CAMS model and ground-based observations from TCCON and NDACC confirms that HIRAS-II retrievals are consistent. The HCOOH-to-CO and the PAN-to-CO column enhancement ratios derived from HIRAS-II are close to those derived from IASI. This paper exhibits the capability of FY-3E/HIRAS-II in observing wildfire emissions during dawn and dusk hours, which will potentially enhance the climate-monitoring capability of low-orbit meteorological satellites.