Data in Figure 1 are from publicly available databases including county-level ammonia (NH3) emissions from the US EPA National Emissions Inventory (https://www.epa.gov/air-emissions-inventories/2014-national-emissions-inventory-nei-data), ambient ammonium (NH4+) aerosol concentrations from the US EPA Clean Air Status and Trends Network (https://java.epa.gov/castnet/clearsession.do), and ambient NH3 concentrations from the National Atmospheric Deposition Program Ammonia Monitoring Network (AMoN) (http://nadp.slh.wisc.edu/data/AMoN/)

Satellite observations of NH3 from the Infrared Atmospheric Sounding Instrument (IASI V2.2R) shown in Figure 2 are also publicly available (https://en.aeris-data.fr/metadata/?dc9dcce0-9324-451b-8d79-2d6df3094068).

Diurnal profiles of ambient NH3 at different sites across the U.S. are summarized in Figure 3. Data from sites operated by EPA Office of Research and Development are attached as a spreadsheet with accompanying data dictionary. Greg Beachley (Beachley.gregory) is the contact for data from the Charleston, SC; Beltsville, MD and Bondville, IL sites. Katherine Benedict (Katherine.Benedict@colostate.edu) is the contact for data from the RMNP; Fort Collins, CO and Greeley, CO sites.

This dataset is associated with the following publication: Puchalski, M., J. Walker, G. Beachley, M. Zondlo, K. Benedict, R. Grant, B. Schichtel, C. Rogers, A. Leytem, J. Rice, K. Morris, J. Schauer, and R. Wang. Need for Improved Monitoring of Spatial and Temporal Trends of Reduced Nitrogen. ENVIRONMENTAL MANAGEMENT. Springer-Verlag, New York, NY, USA, 0, (2019).