Quantifying Spatial and Temporal Variability in Atmospheric Ammonia with In Situ and Space-Based Observations

Robert W. Pinder1, John T. Walker1*, Jesse O. Bash1, Karen E. Cady-Pereira2, Daven K. Henze3, Mingzhao Luo4, Gregory B. Osterman4 and Mark W. Shephard2

Ammonia plays an important role in many biogeochemical processes, yet atmospheric mixing ratios are not well known. The emissions sources are uncertain and it is difficult to measure NH3 in situ. Recently, methods have been developed for retrieving NH3 from space-based observations, yet they have not been compared to in situ measurements. We have conducted a field campaign including co-located surface measurements and satellite special observations from the Tropospheric Emission Spectrometer (TES). Our study includes 25 surface monitoring sites spanning 350 km across eastern North Carolina, a region with large seasonal and spatial variability in NH3 sources and sinks. From the TES spectra, we retrieve a NH3 representative volume mixing ratio (RVMR), and we restrict our analysis to times when the region of the atmosphere observed by TES is representative of the surface measurement. After refining the retrieval, we find that that the TES NH3 RVMR captures the seasonal and spatial variability found in eastern North Carolina. Both surface measurements and TES NH3 show a strong correspondence with the number of livestock facilities within 10 km of the observation. Furthermore, we find that TES NH3 RVMR captures the month-to-month variability present in the surface observations. The high correspondence with in situ measurements and vast spatial coverage make TES NH3 RVMR a valuable tool for understanding regional and global NH3 fluxes.

*Corresponding author: , 919-541-2288
1US EPA Office of Research and Development, Research Triangle Park, North Carolina, USA
2Atmospheric and Environmental Research, Inc., Lexington, Massachusetts, USA
3University of Colorado, Boulder, Colorado, USA
4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, CA, USA