March 2025 Update. Here we provide hourly observations of atmospheric carbon dioxide (CO2), methane (CH4), and (for a few sites) carbon monoxide (CO) from tower-based sites in the NIST Northeast Corridor network. Each *.tgz (tar/gzip) archive contains data files for a given site location, named by its 3-letter code. To extract on a unix platform, use "tar -xvzf ". Data files within the -1-hr-CSV.tgz archives are comma delimited (CSV) 1-hour averages; data files within the -1-hr-NC.tgz archives are 1-hour averages in NetCDF format; data files within the -1-min-CSV.tgz are CSV files with 1-minute averages (there is no NetCDF version for 1-minute data). Site locations, heights, and other information are in a separate ascii (CSV) file (NEC_sites.csv), and also within each data file (for the 1-hour averages files). Data in this archive is for January 1 2015-January 31 2025. ASCII Readme files (Readme_v20250319.txt and Readme_1minfiles_v20250319.txt) contain file information and an Updates_v20250319.pdf file that includes additional information on updates. Note about calibrations: CO2 data are reported on the NOAA/WMO X2019 calibration scale. CH4 data are reported on the NOAA/WMO X2004A calibration scale; CO data, where available, are reported on the NOAA/WMO X2014 scale. Note that previous archives of this data reported CO2 on the X2007 scale. This data is being freely distributed for research, academic and related non-commercial purposes consistent with NIST's mandate to further the science and the promulgation of appropriate standards. Current update: March 19, 2025.

NOTE: please see the latest (March 2025) update at https://doi.org/10.18434/mds2-3765 . This archive is from May 2023. See Updates document for specific major and minor changes. Here we provide hourly observations of carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) from tower-based sites in the NIST Northeast Corridor network. Each *.tgz (tar/gzip) archive contains data files for a given site location, named by its 3-letter code (see NEC_sites.csv for codes and locations). To extract on a unix platform, use "tar -xvzf ". Data files within the .tgz archives are comma delimited (CSV); data files within the _NC.tgz archives are in NetCDF format. Site locations, heights, and other information are in a separate ascii (CSV) file (NEC_sites.csv), and also within each data file. Data in this archive is reported for the years 2015-2022. An ASCII Readme file (NEC_Readme_05052023) is also posted, along with an Updates_05052023.txt file that includes additional information on updates. Note about calibrations: CO2 data are reported on the NOAA/WMO X2007 calibration scale. CH4 data are reported on the NOAA/WMO X2004A calibration scale; CO data, where available, are reported on the NOAA/WMO X2014 scale. This archive, with CO2 data on the X2007 scale, will no longer be updated. A full revision of all the data on the NOAA/WMO X2019 scale for CO2 is forthcoming, and will be linked here; that archive will maintain its own record and DOI, include CH4 and CO, and will be continually updated. This data is being freely distributed for research, academic and related non-commercial purposes consistent with NIST's mandate to further the science and the promulgation of appropriate standards. Current update: May 5, 2023.

Note: This data archive supersedes our previous archive: https://doi.org/10.18434/mds2-2491. See Updates document for specific major and minor changes. Here we provide hourly observations of carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) from tower-based sites in the NIST Northeast Corridor network. Each *.tgz (tar/gzip) archive contains data files for a given site location, named by its 3-letter code (see NEC_sites.csv for codes and locations). To extract on a unix platform, use "tar -xvzf ". Data files within the .tgz archives are comma delimited (CSV); data files within the _NC.tgz archives are in NetCDF format. Site locations, heights, and other information are in a separate ascii (CSV) file (NEC_sites.csv), and also within each data file. Data in this archive is reported for the years 2015-2022. An ASCII Readme file (NEC_Readme_05052023) is also posted, along with an Updates_05052023.txt file that includes additional information on updates. Note about calibrations: CO2 data are reported on the NOAA/WMO X2007 calibration scale. CH4 data are reported on the NOAA/WMO X2004A calibration scale; CO data, where available, are reported on the NOAA/WMO X2014 scale. This archive, with CO2 data on the X2007 scale, will no longer be updated. A full revision of all the data on the NOAA/WMO X2019 scale for CO2 is forthcoming, and will be linked here; that archive will maintain its own record and DOI, include CH4 and CO, and will be continually updated. This data is being freely distributed for research, academic and related non-commercial purposes consistent with NIST's mandate to further the science and the promulgation of appropriate standards. Current update: May 5, 2023.

NOTE: please see the latest (March 2025) update at https://doi.org/10.18434/mds2-3765. Hourly observations of CO2 and CH4 from tower-based sites in the NIST Northeast Corridor network (currently 23, but more may be added in future updates); CO observations from one site. Data files are comma delimited (CSV). Measurements of each species may be from two or more different heights above ground. Site locations, heights, and other information is in a separate ascii (CSV) file (NEC_sites.csv). Data is currently reported for the years 2015-2019, with planned annual updates. An ASCII Readme file (NEC_Readme_10052020) is also posted, along with an Updates_10052020.txt file that includes information on updates. Current update: Nov 11, 2020. See also associated publication (Karion et al., Earth System Science Data, 2020): https://doi.org/10.5194/essd-12-699-2020

WARNING: There is a more recent version of this data set. Please visit https://doi.org/10.18434/mds2-3012 for the update. Do not use this data. Contact Anna.Karion@nist.gov with questions.Hourly observations of CO2 and CH4 from tower-based sites in the NIST Northeast Corridor network (currently 23, but more may be added in future updates); CO observations from one site. Data files are comma delimited (CSV). Measurements of each species may be from two or more different heights above ground. Site locations, heights, and other information is in a separate ascii (CSV) file (NEC_sites.csv). Data is currently reported for the years 2015-2019, with planned annual updates. An ASCII Readme file (NEC_Readme_10052020) is also posted, along with an Updates_10052020.txt file that includes information on updates. Current update: Nov 11, 2020. See also associated publication (Karion et al., Earth System Science Data, 2020): https://doi.org/10.5194/essd-12-699-2020

NOTE: please see the latest (March 2025) update at https://doi.org/10.18434/mds2-3765 . This archive is from November 2021.We have become aware of errors in the inlet heights at multiple sites and have corrected these in the newest version. Hourly observations of CO2 and CH4 from tower-based sites in the NIST Northeast Corridor network; CO observations from one site. Data files are comma delimited (CSV). Measurements of each species may be from two or more different heights above ground. Site locations, heights, and other information is in a separate ascii (CSV) file (NEC_sites.csv). Data in this archive is reported for the years 2015-2020. An ASCII Readme file (NEC_Readme_11012021) is also posted, along with an Updates_11012021.txt file that includes information on updates. In this update, we added a new directory with Obspack-formatted text and netcdf files for users familiar with those data formats (https://gml.noaa.gov/ccgg/obspack/), and have added Kenneth Schuldt (NOAA-GML and CIRES), who generated this ObsPack, to the data citation. These files include all years 2015-2020. Note about calibrations: CO2 data are reported on the NOAA/WMO X2007 calibration scale. CH4 data are reported on the NOAA/WMO X2004A calibration scale; CO data, where available, are reported on the NOAA/WMO X2014 scale. This archive, with CO2 data on the X2007 scale, will no longer be updated. A full revision of all the data on the NOAA/WMO X2019 scale for CO2 is forthcoming, and will be linked here; that archive will maintain its own record and DOI, include CH4 and CO, and will be continually updated. This data is being freely distributed for research, academic and related non-commercial purposes consistent with NIST's mandate to further the science and the promulgation of appropriate standards.Current update: Nov 1, 2021.

WARNING (updated: May 5 2023): This dataset has been updated and is now found at https://doi.org/10.18434/mds2-3012. We have become aware of errors in the inlet heights at multiple sites and have corrected these in the newest version. Hourly observations of CO2 and CH4 from tower-based sites in the NIST Northeast Corridor network; CO observations from one site. Data files are comma delimited (CSV). Measurements of each species may be from two or more different heights above ground. Site locations, heights, and other information is in a separate ascii (CSV) file (NEC_sites.csv). Data in this archive is reported for the years 2015-2020. An ASCII Readme file (NEC_Readme_11012021) is also posted, along with an Updates_11012021.txt file that includes information on updates. In this update, we added a new directory with Obspack-formatted text and netcdf files for users familiar with those data formats (https://gml.noaa.gov/ccgg/obspack/), and have added Kenneth Schuldt (NOAA-GML and CIRES), who generated this ObsPack, to the data citation. These files include all years 2015-2020. Note about calibrations: CO2 data are reported on the NOAA/WMO X2007 calibration scale. CH4 data are reported on the NOAA/WMO X2004A calibration scale; CO data, where available, are reported on the NOAA/WMO X2014 scale. This archive, with CO2 data on the X2007 scale, will no longer be updated. A full revision of all the data on the NOAA/WMO X2019 scale for CO2 is forthcoming, and will be linked here; that archive will maintain its own record and DOI, include CH4 and CO, and will be continually updated. This data is being freely distributed for research, academic and related non-commercial purposes consistent with NIST's mandate to further the science and the promulgation of appropriate standards.Current update: Nov 1, 2021.

Updated April 2025. Here we provide hourly observations of carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) mole fractions in dry air from tower- and rooftop-based sites in the Los Angeles Megacity Carbon Project network. Each *.tgz (tar/gzip) archive contains data files for a given site location, named by its 3-letter code. To extract *.tgz files on a unix platform, use "tar -xvzf ". Data files with in the -1-hr-CSV.tgz archives are comma delimited (CSV) 1-hour averages; data files within the _1-hr-NC.tgz archives are 1-hour averages in NetCDF format; data files within the -1-min-CSV.tgz are CSV files with 1-minute averages (there is no NetCDF version for 1-minute data). Site locations, heights, and other information are in a separate ascii (CSV) file (LAM_sites.csv), and also within each data file (for the 1-hour averages files). We encourage the use of the locations within the hourly data files, as some locations may have changed during the site lifetime and have duplicate entries in the site file. Data in this archive is for January 1 2015-January 31 2025. ASCII Readme files (1Readme_v20250425.txt and 1Readme_1minfiles_v20250425.txt) contain data details; Updates_v20250425.pdf includes additional information on updates since the previous data version. Note about calibrations: CO2 data are reported on the NOAA/WMO X2019 calibration scale. CH4 data are reported on the NOAA/WMO X2004A calibration scale; CO data, where available, are reported on the NOAA/WMO X2014 scale. Note that previous archive s of this data reported CO2 on the X2007 scale. This data is being freely distributed for research, academic and related non-commercial purposes consistent with NIST's mandate to further the science and the promulgation of appropriate standards. Current update: April 25, 2025.

Updated April 2025. Here we provide hourly observations of carbon dioxide (CO2), methane (CH4), and carbon monoxide (CO) mole fractions in dry air from tower- and rooftop-based sites in the Los Angeles Megacity Carbon Project network. Each *.tgz (tar/gzip) archive contains data files for a given site location, named by its 3-letter code. To extract *.tgz files on a unix platform, use "tar -xvzf ". Data files with in the -1-hr-CSV.tgz archives are comma delimited (CSV) 1-hour averages; data files within the _1-hr-NC.tgz archives are 1-hour averages in NetCDF format; data files within the -1-min-CSV.tgz are CSV files with 1-minute averages (there is no NetCDF version for 1-minute data). Site locations, heights, and other information are in a separate ascii (CSV) file (LAM_sites.csv), and also within each data file (for the 1-hour averages files). We encourage the use of the locations within the hourly data files, as some locations may have changed during the site lifetime and have duplicate entries in the site file. Data in this archive is for January 1 2015-January 31 2025. ASCII Readme files (1Readme_v20250425.txt and 1Readme_1minfiles_v20250425.txt) contain data details; Updates_v20250425.pdf includes additional information on updates since the previous data version. Note about calibrations: CO2 data are reported on the NOAA/WMO X2019 calibration scale. CH4 data are reported on the NOAA/WMO X2004A calibration scale; CO data, where available, are reported on the NOAA/WMO X2014 scale. Note that previous archive s of this data reported CO2 on the X2007 scale. This data is being freely distributed for research, academic and related non-commercial purposes consistent with NIST's mandate to further the science and the promulgation of appropriate standards. Current update: April 25, 2025.

Data files in this repository contain a static archive of all the observational and model data required to construct fossil-fuel enhancements at tower sites in Los Angeles (LA_data.csv) and DC-Baltimore (DCBalt_data.csv). These were used in the analyses detailed and presented in the publication "The impact of COVID-19 on CO2 emissions in the Los Angeles and Washington DC/Baltimore metropolitan areas" by Yadav et al.