README -- Describes contents of HEMCO/CH4/2023-07/Gridded_GHGI_v2
24 Aug 2023
GEOS-Chem Support Team
geos-chem-support@g.harvard.edu


Overview:
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These files were obtained from https://zenodo.org/record/7672124 on 24 Aug 2023.

About:

The gridded EPA U.S. anthropogenic methane greenhouse gas inventory (gridded GHGI) includes spatially and temporally resolved (gridded) maps of annual anthropogenic methane emissions (0.1°×0.1°) for the contiguous United States (CONUS). Total gridded methane emissions for each source sector are consistent with national annual U.S. anthropogenic methane emissions reported in the U.S. EPA Inventory of U.S. Greenhouse Gas Emissions and Sinks (U.S. GHGI).

This repository accompanies the preprint manuscript Maasakkers, et al., 2023, which has been submitted as a non peer-reviewed preprint to EarthArXiv. This repository is an update to the gridded GHGI version 1, previously described in Maasakkers, et al., (2016) and currently available on the U.S. EPA website. The EPA website will be updated with version 2 of the gridded GHGI upon review and final publication of the manuscript.

This repository contains two datasets:

1. Gridded GHGI Data (main dataset; 2 file types).

   Gridded annual U.S. anthropogenic methane emissions for 2012-2018 for 26 source categories, hereafter called the gridded GHGI. This dataset is developed to be consistent with the national U.S. GHGI published in 2020 (U.S. EPA , Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990 - 2020. U.S. Environmental Protection Agency, 2020, EPA 430-R-22-003, https://www.epa.gov/ghgemissions/inventory-us-greenhouse-gas-emissions-and-sinks-1990-2018) (hereafter called the U.S. GHGI). This gridded dataset represents an update to the original version 1 of the gridded GHGI from Maasakkers, et al., (2016). The annual files contain one year of emissions per source category but include a time dimension to make them suitable (COARDS-compliant) for atmospheric models. This main dataset also includes monthly source-specific methane emission scaling factors for those select sources with strong interannual variability.

   a. Annual emission flux files containing individual variables for the 26 different source categories.
     (dimensions: time x lat x lon; units: molec. CH­4 cm-2 s-1):
      - Gridded_GHGI_Methane_v2_YYYY.nc

   b. Monthly scaling factor files containing individual variables for the different source categories that have strong interannual variability. These scaling factors can be multiplied with the data in the annual emission files to get monthly methane emission fluxes for these select source categories.
      (dimensions: time x lat x lon; units: dimensionless): 
      - Gridded_GHGI_Methane_v2_Monthly_Scale_Factors_YYYY.nc
 
2. Gridded GHGI Express Extension (1 file type).

   Gridded annual U.S. anthropogenic methane emissions for 2012-2020 for 27 source categories (one additional source category compared to the main dataset above), hereafter called the express extension. This dataset is developed for total methane emissions to be consistent with the U.S. GHGI published in 2022 (EPA (2022) Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990-2020. U.S. Environmental Protection Agency, EPA 430-R-22-003. https://www.epa.gov/ghgemissions/draft-inventory-us-greenhouse-gas-emissionsand-sinks-1990-2020). This dataset is *not* a full update to the main gridded GHGI dataset, and instead uses annual source-specific spatial patterns from 2012-2018 from the main dataset to quickly incorporate more recent national methane emission estimates. Emissions for years after 2018 follow the 2018 spatial patterns.

   a. Annual emission files
      (dimensions: time x lat x lon; units: molec. CH­4 cm-2 s-1):
      - Express_Extension_Gridded_GHGI_Methane_v2_YYYY.nc