Advancing Atmospheric Detection of Weakly Absorbing Reactive Trace Gases Using the FY-3E/HIRAS-II TIR Sounder on a Dawn-Dusk Orbit.

Weakly absorbing reactive trace gases play important roles in the atmospheric environment and usually have short lifetimes ranging from seconds to days. HIRAS-II, the second hyperspectral infrared atmospheric sounder aboard the world's first civilian meteorological satellite in dawn-dusk orbit, FengYun-3E (FY-3E), can theoretically detect more than a dozen weakly absorbing reactive trace gases and make important contributions to global trace gas mapping by filling the gap for diurnal variation. This study uses state-of-the-art weak absorber thermal infrared spectral feature quantification and identification methods to detect weak absorbers from FY-3E/HIRAS-II and successfully capture 14 species from 35.4 million FY-3E/HIRAS-II clear-sky measurements in July 2023. We map the reliable global distribution of spectral features from nine routine reactive gases and find that these gases originate from scenes that are usually of special concern, including densely populated areas, vegetation, and biomass burning. This study confirms the capability of FY-3E/HIRAS-II in detecting weak absorbers and serves as a stepping stone for subsequent research in concentration retrieval. The case of the ammonia column over wildfires retrieved using neural network technology initially demonstrates that FY-3E/HIRAS-II can improve our understanding of the diurnal variation of trace gases by complementing measurements at dawn and dusk.