Validation of NH3 observations from AIRS and CrIS against measurements from DISCOVER-AQ and the Magic Valley

Authors: CADY-PERERIA, KAREN - Atmospheric And Environmental Research; GUO, XUEHUI - Princeton University; WANG, RUI - Princeton University; Leytem, April; CALKINS, CHASE - Atmospheric And Environmental Research; BERRY, ELIZABETH - Atmospheric And Environmental Research; SUN, KANG - University Of Buffalo; PAYNE, VIVIENNE - Jet Propulsion Laboratory; KULAWIK, SUSAN - Jet Propulsion Laboratory; ZONDLO, MARK - Princeton University; KANTCHEV, VALENTIN - Jet Propulsion Laboratory

Submitted to: Atmospheric Measurement Techniques
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/2/2023
Publication Date: 1/5/2024
Citation: Cady-Pereria, K., Guo, X., Wang, R., Leytem, A.B., Calkins, C., Berry, E., Sun, K., Payne, V., Kulawik, S., Zondlo, M., Kantchev, V. 2024. Validation of NH3 observations from AIRS and CrIS against measurements from DISCOVER-AQ and the Magic Valley. Atmospheric Measurement Techniques. 17(1):15-36. https://doi.org/10.5194/amt-17-15-2024.
DOI: https://doi.org/10.5194/amt-17-15-2024

Interpretive Summary: Ammonia is one of the most common forms of reactive nitrogen and the primary alkaline gas in the atmosphere. Intended and unintended releases of ammonia into the environment over the last century have significantly altered the natural nitrogen cycle, so that the current emission levels of ammonia are about four times higher than in previous centuries. Ammonia is the dominant base in the atmosphere, and it plays a significant role in the formation of fine particulate matter (PM2.5) which can penetrate deep into the lungs and severely impact the respiratory and circulatory systems. In situ measurement of ammonia remains a challenge as ammonia is easy to detect, but it is hard to measure accurately. The high spatial and temporal variability of ammonia exacerbates the lack of continuous, spatially well sampled data over extensive regions. Satellite data, even though they come with their own uncertainties, provide by virtue of their spatial and temporal density, another option for quantifying ammonia emissions. Our objective was to add to the satellite validation record at the single pixel scale, using aircraft and ground ammonia measurements with satellite retrievals from both the Atmospheric Infrared Sounder (AIRS) and Cross-track Infrared Sounder (CrIS) instruments. The AIRS and CrIS profiles individually have large uncertainties, which are driven by local conditions, most significantly temperature profiles and sub-pixel heterogeneity. However, average biases between satellite and aircraft data, after smoothing errors are accounted for, are below or close to 1 ppbv. Use of ground base measurements for validation clearly demonstrate the importance of having more than a few dozen data points to obtain useful information from space-based retrievals of ammonia. With 464 observations over three years, over a small region, it was possible to obtain a clear picture of the source distribution in the region through the application of a physics based oversampling algorithm.

Technical Abstract: Ammonia is one of the most common forms of reactive nitrogen and the primary alkaline gas in the atmosphere. Intended and unintended releases of ammonia into the environment over the last century have significantly altered the natural nitrogen cycle, so that the current emission levels of ammonia are about four times higher than in previous centuries. Ammonia is the dominant base in the atmosphere, and it plays a significant role in the formation of fine particulate matter (PM2.5) which can penetrate deep into the lungs and severely impact the respiratory and circulatory systems. In situ measurement of ammonia remains a challenge as ammonia is easy to detect, but it is hard to measure accurately. The high spatial and temporal variability of ammonia exacerbates the lack of continuous, spatially well sampled data over extensive regions. Satellite data, even though they come with their own uncertainties, provide by virtue of their spatial and temporal density, another option for quantifying ammonia emissions. Our objective was to add to the satellite validation record at the single pixel scale, using aircraft and ground ammonia measurements with satellite retrievals from both the Atmospheric Infrared Sounder (AIRS) and Cross-track Infrared Sounder (CrIS) instruments. The AIRS and CrIS profiles individually have large uncertainties, which are driven by local conditions, most significantly temperature profiles and sub-pixel heterogeneity. However, average biases between satellite and aircraft data, after smoothing errors are accounted for, are below or close to 1 ppbv. Use of ground base measurements for validation clearly demonstrate the importance of having more than a few dozen data points to obtain useful information from space-based retrievals of ammonia. With 464 observations over three years, over a small region, it was possible to obtain a clear picture of the source distribution in the region through the application of a physics based oversampling algorithm.