Gridded EPA U.S. Anthropogenic Methane Greenhouse Gas Inventory (gridded GHGI)

About
The gridded EPA U.S. anthropogenic methane greenhouse gas inventory (gridded methane 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 emission 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). More information is available on the U.S. EPA website. 
This repository accompanies the peer-reviewed manuscript Maasakkers, et al., 2023. Data in this repository are an update to the gridded GHGI version 1, previously described in Maasakkers, et al., 2016 and available on the U.S. EPA website. 
This repository contains two data products:

Gridded GHGI v2 (main product; 2 file types). Gridded annual U.S. anthropogenic methane emissions for 2012-2018 for 26 source categories (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).This dataset includes 2 file types: a. Annual methane emission fluxes for 26 inventory source categories. Files contain one year of emissions per source category and include a time dimension variable to make the data suitable (COARDS-compliant) for atmospheric models.   (Dimensions: latitude x longitude x time; units: molecules CH­4 cm-2 s-1):     - Gridded_GHGI_Methane_v2_YYYY.ncb. Monthly emission scaling factors for inventory source categories with strong interannual variability (see 'Data Details' below). To use these factors to calculate absolute monthly methane emission fluxes, multiply the scaling factors for each relevant source category by the corresponding emission fluxes in the annual flux files. (Dimensions: latitude x longitude x month; units: dimensionless):      - Gridded_GHGI_Methane_v2_Monthly_Scale_Factors_YYYY.nc 
Gridded GHGI v2 Express Extension (1 file type). The v2 Express Extension includes gridded annual U.S. anthropogenic methane emissions for 2012-2020 for 27 source categories (one additional source category compared to the main v2 dataset above). This dataset is developed to be consistent with total methane emissions from 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). **Note**: This dataset is not a full update to the main gridded GHGI v2 product. To quickly incorporate more recent national methane emission estimates into gridded products, national methane emissions from a more recent U.S. GHGI were spatially allocated (i.e., gridded) using the annual source-specific spatial emission patterns developed for the 2012-2018 main v2 product. Emissions for years 2019 and 2020 were allocated using 2018 spatial patterns.This dataset includes 1 file type:a. Annual emission files   (Dimensions: latitude x longitude x time; units: molecules CH­4 cm-2 s-1):     - Express_Extension_Gridded_GHGI_Methane_v2_YYYY.nc
--------------------------------------------------