README FOR FANv2 INPUT AND OUTPUT DATA FILES 

These files are provided as part of supplementary information to the manuscript of Vira et
al. (2019) "An improved mechanistic model for ammonia volatilization in Earth system
models: Flow of Agricultural Nitrogen, version 2 (FANv2)", submitted for publication in
Geoscientific Model Development.

1. FAN input stream

The netcdf file fan_nitrogen_f19_c20190325.nc contains the input data specific to FAN as
required for simulating global NH3 emissions. The variables describe gridded fractions of
different synthetic fertilizers, topsoil pH, and manure nitrogen excretion.

The fertilizer fractions are fract_nitr (fraction of NO3-N), fract_urea (fraction of
urea-N). The remaining nitrogen is attributed to other ammonium-N. The file also contains
the fraction of anhydrous ammonia nitrogen (fract_drct) but this is not currently used by
the model. The fertilizer data are extracted from the consumption statistics of the
International Fertilizer Association (IFA, www.fertilizer.org).

The manure N excretion is split to three categories: manure_grz (manure of year-round
grazing animals), manure_sgrz (manure of seasonally grazing animals) and manure_ngrz
(manure of non-grazing animals). The gridded excretion rates are based on the Gridded
Livestock of the World v2.0 and the Global Ruminant Production Systems version 5 datasets
published by FAO. The unit of the manure fields is kgN/m2/year.

Finally, the file contains a gridded soil pH map originally extracted from the Harmonized
World Soil Database, first regridded as described in
http://dx.doi.org/10.3334/ORNLDAAC/1247 and subsequently averaged to the f19
(approximately 2 degree) resolution used in CESM.

2. NH3 emissions

The netcdf file nh3_emission_c20200524.nc contains gridded, monthly agricultural ammonia emissions
simulated by the FANv2 model. The emissions are obtained by averaging a CLM simulation for
2010-2015.

The netcdf variables represent the gridded emission fluxes on two levels of
aggregation as follows:

- The total agricultural emission is the sum of manure and synthetic fertilizer sources:
  NH3_TOTAL = NH3_MANURE + NH3_FERT

- The fertilizer emissions consist of urea and other fertilizers:
  NH3_FERT = NH3_UREA + NH3_OTHERFERT

- The manure emissions consist of grazing, barns, stores, and manure applications:
  NH3_MANURE = NH3_GRZ + NH3_BARNS + NH3_STORES + NH3_MAN_APP

The amounts corresponding to the reporting categories "manure management" and
"agricultural soils" are not given in the file, but can be calculated as

MANURE MANAGEMENT = NH3_BARNS + NH3_STORES

and

AGRICULTURAL SOILS = NH3_GRZ + NH3_MAN_APP + NH3_FERT

All fluxes are given in gN/m2/sec, where the density is with regard to total surface
(including land and ocean) area in the grid cell.

For more information, please contact the authors:

Julius Vira, julius.vira@gmail.com
Peter Hess, pgh25@cornell.edu

