Description of data files accompanying:
Global nitrogen deposition (2°×2.5° grid resolution) simulated with GEOS-Chem for 1984-1986, 1994-1996, 2004-2006, and 2014-2016

Author: Daniel E Ackerman
30 May, 2018

The NetCDF files contain the raw output of the GEOS-Chem models for each year (indicated in the file name) of the simulation. These NetCDF files contain detailed information on specific atmospheric chemical species involved in wet or dry deposition. For more information about the naming conventions of chemical species and atmospheric processes within the NetCDF files, see the GEOS-Chem Wiki page (http://wiki.seas.harvard.edu/geos-chem/index.php/Main_Page). NetCDF files are readable by a range of programs, including Panoply (https://www.giss.nasa.gov/tools/panoply/download/) and the R package 'netcdf4'.

Raw Outputs of the GEOS-Chem models for each year

We used the GEOS-Chem chemical transport model (v11-01; www.geos-chem.org) to generate the NetCDF files containing simulated global atmospheric deposition data for 1984-1984, 1994-1996, 2004-2006, and 2014-2016 at a spatial resolution of 2˚×2.5˚. GEOS-Chem was driven with meteorological data (the Modern-Era Retrospective analysis for Research and Applications, Version 2; MERRA-2; Gelaro et al. 2017) from the NASA Global Modeling and Assimilation Office at a degraded horizontal resolution of 2˚×2.5˚ with 47 vertical layers. Anthropogenic emissions scenarios used in the model are from the Emission Database for Global Atmospheric Research (EDGAR v4.2; edgar.jrc.ec.europa.eu/overview.php?v=42) inventory, which covers the years from 1970 to 2010. For later years, we used the 2010 anthropogenic emissions. The GEOS-Chem model was run at the Minnesota Supercomputing Institute (http://www.msi.umn.edu) at the University of Minnesota

Gelaro, R., McCarty, W., Suárez, M. J., Todling, R., Molod, A., Takacs, L., ... & Wargan, K. (2017). The modern-era retrospective analysis for research and applications, version 2 (MERRA-2). Journal of Climate, 30(14), 5419-5454.


Inorganic Nitrogen Deposition
The .csv file 'inorganic_N_deposition.csv' contains spatially-explicit information about dry, wet, and total (dry + wet) inorganic nitrogen deposition in each grid cell for each year simulated. Chemical species included in the wet deposition calculations were NH3, NH4, NO3, and HNO3. Dry deposition calculations included these species plus N2O5 and NO2. Rows represent individual grid cells from the simulation. Metadata about specific columns is as follows:
1. 'latitude': latitude value (decimal degrees) of center of simulated grid cell
2. 'longitude': longitude value (decimal degrees) of center of simulated grid cell
3. 'pixel_area_km2': Area of the simulated grid cell in units of square kilometers
4-39. These columns provide the amount of inorganic nitrogen (kilograms of nitrogen per square kilometer per year) deposited from atmosphere to land in a specified year. In the column title, the type of deposition ('wet', 'dry', or 'total') is separated from the year with an underscore. For example, each case within the column 'wet_1984' shows the amount of inorganic nitrogen deposited through wet deposition in the year 1984 for each grid cell.

Organic Nitrogen Deposition
The .csv file 'organic_N_deposition.csv' contains spatially-explicit information about dry, wet, and total (dry + wet) organic nitrogen deposition in each grid cell for each year simulated. Chemical species included in the simulations are propanone nitrate, isoprene hydroxynitrate, methyl vinyl ketone + methacrolein nitrates, ≥C4 alkylnitrates, methyl peroxy nitrate, peroxyacetylnitrate, peroxypropionylnitrate, and peroxymethacryloyl nitrate. GEOS-Chem does not simulate certain biogenic nitrogen-bearing compounds, such as amino acids and urea, which can constitute a significant component of organic nitrogen deposition. Therefore, our estimates of organic nitrogen deposition should be considered lower-bound estimates. Rows represent individual grid cells from the simulation. Metadata about specific columns is as follows:
1. 'latitude': latitude value (decimal degrees) of center of simulated grid cell
2. 'longitude': longitude value (decimal degrees) of center of simulated grid cell
3. 'pixel_area_km2': Area of the simulated grid cell in units of square kilometers
4-39. These columns provide the amount of organic nitrogen (kilograms of nitrogen per square kilometer per year) deposited from atmosphere to land in a specified year. In the column title, the type of deposition ('wet', 'dry', or 'total') is separated from the year with an underscore. For example, each case within the column 'wet_1984' shows the amount of organic nitrogen deposited through wet deposition in the year 1984 for each grid cell.

Oxidized and Reduced Inorganic Nitrogen Deposition
The .csv file 'oxidized_reduced_N_deposition.csv' contains spatially-explicit information about dry, wet, and total (dry + wet) inorganic nitrogen deposition in chemically reduced and chemically oxidized species for each grid cell in each year simulated. Rows represent individual grid cells from the simulation. Metadata about specific columns is as follows:
1. 'latitude': latitude value (decimal degrees) of center of simulated grid cell
2. 'longitude': longitude value (decimal degrees) of center of simulated grid cell
3. 'pixel_area_km2': Area of the simulated grid cell in units of square kilometers
4-75. These columns provide the amount of inorganic nitrogen (kilograms of nitrogen per square kilometer per year) deposited from atmosphere to land  in either oxidized or reduced chemical forms. Each column title has three descriptive parts, separated by under scores. The first part of the column title indicates the type of deposition: 'dry', 'wet', or 'total' (wet + dry). The second part of the column title indicates the chemical form: 'oxidized' or 'reduced'. The third part of the column title indicates the year. For example, each case within the column 'dry_reduced_1984' shows the amount of inorganic nitrogen deposited through dry deposition in reduced chemical forms in the year 1984 for the corresponding grid cell.