README file date: 06-27-2019

Dataset title: Simulated CO2 dataset using the atmospheric transport model GEOSChem v12.0.0: Response to regional land carbon fluxes 
Dataset authors: Samantha Basile, Xin Lin, Gretchen Keppel-Aleks
Dataset time range: monthly, 01-01-1980 - 12-01-2010

Research purpose:
We ran the GEOS-Chem v12.0.0 atmospheric transport model (https://doi.org/10.5281/zenodo.1343547; http://wiki.seas.harvard.edu/geos-chem/index.php/GEOS-Chem_12#12.0.0) to simulate the imprint CASA testbed land fluxes on atmospheric CO2 (testbed fluxes described in Wieder et al., 2018; https://doi.org/10.1111/gcb.13979).

Methods: 
Testbed fluxes of soil heterotrophic respiration (HR) and net primary productivity (NPP) are used as boundary conditions for the transport model (testbed fluxes described in Wieder et al., 2018; https://doi.org/10.1111/gcb.13979). This file contains the monthly averaged atmospheric CO2 mole fraction simulated by the GEOSChem v12.0.0 model for 01-01-1980 to 12-01-2010. Results of the first two years (1980 and 1981) are reserved for model spin-up.

The GEOSChem v12.0.0 model was run with:
resolution of 2.0° in latitude by 2.5° in longitude with 47 vertical levels,
dynamic timestep set to be 600 seconds,
initialization of a globally-uniform atmospheric CO2 mole fraction equal to 350 ppm, 
hourly meteorological fields from the Modern-Era Retrospective analysis for Research and Application version 2 (MERRA2) reanalysis data (Gelaro et al.,2017; https://doi.org/10.1175/JCLI-D-16-0758.1; https://gmao.gsfc.nasa.gov/reanalysis/MERRA-2/).


File Inventory: 
GEOSChem_concat_SpeciesConc_1980to2010.nc: This netcdf file contains atmospheric mole fractions for CO2 in response to land fluxes of carbon for the period of January 1980 to December 2010.

GEOSChem.SpeciesConc.20100101_0000z.nc4: This file contains the atmospheric CO2 mole fractions that are included in the concatenated Species Concentration file (GEOSChem_concat_SpeciesConc_1980to2010.nc). This file was included here because it also contains the variables a: hyam b: hybm p0: P0 ps: PS which could be used to convert the hybrid levels to pressure levels in millibars. 

Definition of Terms and Variables: 
Simulated atmospheric CO2 in this file is tagged by:
1. the underlying land flux: net primary productivity (NPP from the CASA-CNP soil model; https://doi.org/10.1111/gcb.13979) and soil hetertrophic respiration (HR from the CASA-CNP, CORPSE, MIMICS soil models; https://doi.org/10.1111/gcb.13979), 
2. the land flux source region: Northern Hemisphere high latitudes (NHL; 61 to 90°N), midlatitudes (NML; 24 to 60°N), tropics (NT; 1 to 23°N), Southern Hemisphere tropics (ST; 0 to 23°S), and extratropics (SE; 24 to 90°S). 

The latband variable corresponds to the land flux source regions in the following way:
latband(1): Northern Hemisphere high latitudes (NHL; 61 to 90°N).
latband(2): Northern Hemisphere midlatitudes (NML; 24 to 60°N).
latband(3): Northern Hemisphere tropics (NT; 1 to 23°N).
latband(4): Southern Hemisphere tropics (ST; 0 to 23°S).
latband(5): Southern Hemisphere extratropics (SE; 24 to 90°S). 

The level variable is calculated at hybrid sigma-pressure in the atmosphere. A separate file is also uploaded with the variables a: hyam, b: hybm, p0: P0, ps: PS, if the user would like to convert the hybrid levels to pressure levels in millibars. The concatenated file (GEOSChem_concat_SpeciesConc_1980to2010.nc) does include a converted pressure varible, so the hyam, hybm, p0, P0, ps variables are included in this upload for continuity.