New Cross-Track Infrared Sounder (CrIS) Satellite Observations of Ammonia: Retrievals, Validation, and Spatiotemporal Variability

Ammonia (NH₃) is a highly reactive, short-lived pollutant and a key component of the nitrogen cycle. Its principal sources are agricultural activities, namely fertilizer application and livestock waste. Biomass burning events also generate large amounts of NH₃ and in urban areas automobiles with three-way catalytic converters can be a major source. NH₃ plays a significant role in the formation of PM_2.5 particles, which can penetrate deep into the lungs and severely impact the respiratory and circulatory systems. Paulot and Jacob (2014) have recently shown that the costs associated with the health impacts of NH₃ connected with food production for export in the US more than offset the revenue from these exports. The demand for more and better food by an increasing world population is driving the rapid growth of industrial-scale agriculture, especially in Asia, and this is expected to lead to significantly higher NH₃concentrations, which will not only impact air quality but will also disrupt land and water ecosystems through increased dry and wet deposition of nitrogen.

Despite this importance there are still large uncertainties in our knowledge of the sources and spatiotemporal distributions of NH₃. This is mainly attributed to its “sticky” nature, which makes it difficult and expensive to accurately measure using conventional in-situ surface methods in a dense network, especially in remote locations. Recent satellite observations of NH₃ combined with available ground-based observations can fill this monitoring gap, and improve our knowledge of NH₃ emission sources, distributions, and deposition to the ecosystem. Ultimately these satellite observations will lead to improvements in air quality forecast models and their input emission inventories.

We will present the satellite-based NH₃ retrieval from the Cross-Track Infrared Sounder (CrIS) instrument, launched on 28 October 2011 on USA NOAA/NASA/DoD the polar-orbiting Suomi National Polar-orbiting Partnership (NPP) satellite, which provides twice daily (~01:30 and 13:30 standard local time) global observations. The CrIS instrument provides excellent radiometric capabilities to monitor near surface ammonia observations due to low noise characteristics in the NH₃ spectral region (~3-4x better than other comparable instruments). We will discuss the initial validations and results from Version 1 of recently developed CrIS Fast Physical Retrieval (CFPR) (Shephard and Cady-Pereira, 2015) NH₃ satellite algorithm, which is to be implemented into a NASA operational algorithm in the coming year. The retrieval uses the very fast Optimal Spectral Sampling (OSS) radiative transfer forward model with an optimal estimation approach to provide a retrieved profile and a corresponding measurement of vertical sensitivity (averaging kernels), and an estimate of the retrieval errors, which vary from profile-to-profile depending on the atmospheric state. In order to evaluate the uncertainties in the CrIS Fast Physical Retrieval (CFPR) NH₃ satellite observations we compare will them against other available observation sources: ground-based observations that include: (i) profiles and column measurements from FTIR sites in the Network for the Detection of Atmospheric Composition Change (NDACC) around the globe (Dammers et al., 2017), (ii) surface in-situ Ammonia Monitoring Network (AMoN) observations across North America, including 3 Canadian Air and Precipitation Monitoring Network (CAPMON) sites, and aircraft observations from the California and Colorado DISCOVER-AQ campaigns. These results show that the CFPR retrieval provides boundary-layer concentrations at a nadir spatial resolution of ~12 km² (~14 km circle at nadir that grows in an elliptical pattern off nadir) with an uncertainty of about 30%. We will also provide spatiotemporal maps of ammonia across North America that highlight the regionally intense emissions from agriculture practices and forest fires.

References

Dammers, E., Shephard, M. W., Palm, M., Cady-Pereira, K., Capps, S., Lutsch, E., Strong, K., Hannigan, J. W., Ortega, I., Toon, G. C., Stremme, W., Grutter, M., Jones, N., Smale, D., Siemons, J., Hrpcek, K., Tremblay, D., Schaap, M., Notholt, J., and Erisman, J. W.: Validation of the CrIS fast physical NH₃ retrieval with ground-based FTIR, Atmos. Meas. Tech., 10, 2645-2667, https://doi.org/10.5194/amt-10-2645-2017, 2017.

Paulot, F., & Jacob, D. J. (2014). Hidden cost of US agricultural exports: particulate matter from ammonia emissions. Environmental science & technology, 48 (2), 903-908

Shephard, M. W. and K.E. Cady-Pereira: Cross-track Infrared Sounder (CrIS) satellite observations of tropospheric ammonia, Atmos. Meas. Tech., 8, 1323-1336, doi:10.5194/amt-8-1323-2015, 2015.