DOI: 10.13020/d6kx2r
title: Global nitrogen deposition (2°×2.5° grid resolution) simulated with GEOS-Chem for 1984-1986, 1994-1996, 2004-2006, and 2014-2016

description: Atmospheric deposition of inorganic nitrogen is critical to the function of ecosystems and elemental cycles. During the industrial period, humans have doubled the amount of inorganic nitrogen in the biosphere and radically altered rates of atmospheric nitrogen deposition. Despite this rapid change, estimates of global nitrogen deposition patterns generally have low, centennial-scale temporal resolution. Lack of information on annual- to decadal-scale changes in global nitrogen deposition makes it difficult for scientists researching questions on these finer timescales to contextualize their work within the global nitrogen cycle. Here we use the GEOS-Chem Chemical Transport Model to estimate wet and dry deposition of inorganic nitrogen globally at a spatial resolution of 2°×2.5° for 12 individual years in the period from 1984 to 2016. During this time, we found a 12% increase in global inorganic nitrogen deposition from 86.6 TgN yr-1 to 96.9 TgN yr-1, a trend that comprised a balance of variable regional patterns. For example, inorganic nitrogen deposition increased in areas including east Asia and Southern Brazil, while inorganic nitrogen deposition declined in areas including the central Indo-Pacific and Europe. Further, we found a global increase in the percentage of inorganic nitrogen deposited in chemically reduced forms from 31.5% to 34.1%, and this trend was largely driven by strong regional increases in the proportion of chemically reduced nitrogen deposited over the United States. This study provides spatially explicit estimates of inorganic nitrogen deposition over the last four decades and improves our understanding of short-term human impacts on the global nitrogen cycle.

We provide all output from these GEOS-Chem simulations related to atmospheric deposition.
description: The NetCDF files (.nc) 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'.

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. 
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. 

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.