The First Global Map of Atmospheric Ammonia (NH3) as Observed by the HIRAS/FY-3D Satellite

Atmospheric ammonia (NH₃) is a chemically active trace gas that plays an important role in the atmospheric environment and climate change. Satellite remote sensing is a powerful technique to monitor NH₃ concentration based on the absorption lines of NH₃ in the thermal infrared region. In this study, we establish a retrieval algorithm to derive the NH₃ column from the Hyperspectral Infrared Atmospheric Sounder (HIRAS) onboard the Chinese FengYun (FY)-3D satellite and present the first atmospheric NH₃ column global map observed by the HIRAS instrument. The HIRAS observations can well capture NH₃ hotspots around the world, e.g., India, West Africa, and East China, where large NH₃ emissions exist. The HIRAS NH₃ columns are also compared to the space-based Infrared Atmospheric Sounding Interferometer (IASI) measurements, and we find that the two instruments observe a consistent NH₃ global distribution, with correlation coefficient (R) values of 0.28–0.73. Finally, some remaining issues about the HIRAS NH₃ retrieval are discussed.