Hourly methane mole fraction data collected from four tower sites in the Washington DC and Baltimore MD region as part of NIST's Northeast Corridor project. Dataset accompanying publication "Seasonally resolved excess urban methane emissions from the Baltimore/Washington, DC metropolitan region" by Huang, Y., Kort, E. A., Gourdji, S., Karion, A., Mueller, K., and Ware, J.: Seasonally Resolved Excess Urban Methane Emissions from the Baltimore/Washington, DC Metropolitan Region, Environ. Sci. Technol., 10.1021/acs.est.9b02782, 2019. Data is described further in the publication and readme document.

Methane (CH4) mole fraction data collected from three tower sites in the Washington DC area: Bucktown, MD (BUC, ghg01), Stafford, VA (SFD, ghg65), and Thurmont, MD (TMD, ghg61), as part of NIST's Northeast Corridor Urban Testbed project, presented as 1-minute averages. This data is published for research academic and related non-commercial purposes consistent with NIST?s mandate to further the science and the promulgation of appropriate standards. This dataset was used in the following publication and this archive represents the static archive of the data used in the publication and is not updated or modified: Sahu, S., Ahn, D., Loughner, C., and Dickerson, R., "Influence of synoptic weather patterns on methane mixing ratios in the Baltimore/Washington region", Atmospheric Environment, Volume 334, 2024, 120675, ISSN 1352-2310,https://doi.org/10.1016/j.atmosenv.2024.120675.Data is described further in the Readme document and references cited within.

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.

Dataset accompanying publication:Martin, C. R., Zeng, N., Karion, A., Mueller, K., Ghosh, S., Lopez-Coto, I., Gurney, K. R., Oda, T., Prasad, K., Liu, Y., Dickerson, R. R., and Whetstone, J.: Investigating sources of variability and error in simulations of carbon dioxide in an urban region, Atmos. Environ., https://doi.org/10.1016/j.atmosenv.2018.11.013, 2018.Data files presented here include both carbon dioxide (CO2) mole fraction observations from NIST-Earth Networks tower stations in the region surrounding Washington, D.C. and Baltimore, MD and modeled mole fractions for these same sites. Please refer to the publication above for all details, including locations of sites, and abbreviations of models and site codes. Observations from SNP are not included, as they can be obtained from NOAA/ESRL.Model Output Files:All files are comma-delimited text files. The filename indicates the site (three letter code: SNP, ARL, NDC, HAL), followed by the inlet height above ground (in meters), followed by the name of the inventory (Vulcan, ODIAC, ODIACFIX, EDGAR, FFDAS, VEGAS), or Back, indicating the incoming CO2 mole fraction background. The total modeled CO2 mole fractions, for example, for FFDAS, are the sum of Back, VEGAS, and FFDAS tracers.Example: HAL_29_FFDAS.csv contains the CO2 mole fraction contribution at HAL at 29m from the FFDAS inventory. The sum shown in the paper is HAL_29_FFDAS + HAL_29_Back + HAL_29_VEGAS.Model output files contain two columns:The date-time stamp (UTC), and the CO2 mole fraction in micromoles of CO2 per mole of dry air, or ppm.Observation Files:CO2 Measurements are reported on the WMO X2007 (CO2) scales. Refer to Verhulst et al, 2017 for measurement and calibration details.Verhulst, K. R., A. Karion, J. Kim, P. K. Salameh, R. F. Keeling, S. Newman, J. Miller, C. Sloop, T. Pongetti, P. Rao, C. Wong, F. M. Hopkins, V. Yadav, R. F. Weiss, R. M. Duren and C. E. Miller (2017), Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project Part 1: calibration, urban enhancements, and uncertainty estimates, Atmos. Chem. Phys., 17(13), 8313-8341, doi:10.5194/acp-17-8313-2017.Each file name is encoded with the site, year, revision number and date, as follows:For all sites, all file names follow this naming scheme:[site]-[year]-[gas]-[measurement height]-[averaging-interval]-[revision date].csvExample: ARL-2016-co2-100m-1-hour-20160504.csvColumn Headers (with description) for observation CO2 files:datetime_UTC (date, dd-mm-yyyy HH:MM:SS)dec_year_UTC (decimal year)yyyy (year)mm (month)dd (day)HH (hour, UTC)co2_ppm (dry air mole fraction, ppm, averaged over the hour following the time stamp)co2_SD (standard deviation of air data in 1 hour)co2_n_minutes (number of 1-minute values in each 1-hour average)co2_min (ppm, minimum 1-min value in each 1-hour)co2_max (ppm, maximum 1-min value in each 1-hour)co2_uncertainty (ppm, 1-sigma measurement uncertainty)co2_flags (data quality flag: "..P" indicates preliminary data, which might change if a final calibration is applied at a later date)

Dataset accompanying publication: Martin, C. R., Zeng, N., Karion, A., Mueller, K., Ghosh, S., Lopez-Coto, I., Gurney, K. R., Oda, T., Prasad, K., Liu, Y., Dickerson, R. R., and Whetstone, J.: Investigating sources of variability and error in simulations of carbon dioxide in an urban region, Atmos. Environ., https://doi.org/10.1016/j.atmosenv.2018.11.013, 2018. Data files presented here include both carbon dioxide (CO2) mole fraction observations from NIST-Earth Networks tower stations in the region surrounding Washington, D.C. and Baltimore, MD and modeled mole fractions for these same sites. Please refer to the publication above for all details, including locations of sites, and abbreviations of models and site codes. Observations from SNP are not included, as they can be obtained from NOAA/ESRL. Model Output Files: All files are comma-delimited text files. The filename indicates the site (three letter code: SNP, ARL, NDC, HAL), followed by the inlet height above ground (in meters), followed by the name of the inventory (Vulcan, ODIAC, ODIACFIX, EDGAR, FFDAS, VEGAS), or Back, indicating the incoming CO2 mole fraction background. The total modeled CO2 mole fractions, for example, for FFDAS, are the sum of Back, VEGAS, and FFDAS tracers. Example: HAL_29_FFDAS.csv contains the CO2 mole fraction contribution at HAL at 29m from the FFDAS inventory. The sum shown in the paper is HAL_29_FFDAS + HAL_29_Back + HAL_29_VEGAS. Model output files contain two columns: The date-time stamp (UTC), and the CO2 mole fraction in micromoles of CO2 per mole of dry air, or ppm. Observation Files: CO2 Measurements are reported on the WMO X2007 (CO2) scales. Refer to Verhulst et al, 2017 for measurement and calibration details. Verhulst, K. R., A. Karion, J. Kim, P. K. Salameh, R. F. Keeling, S. Newman, J. Miller, C. Sloop, T. Pongetti, P. Rao, C. Wong, F. M. Hopkins, V. Yadav, R. F. Weiss, R. M. Duren and C. E. Miller (2017), Carbon dioxide and methane measurements from the Los Angeles Megacity Carbon Project Part 1: calibration, urban enhancements, and uncertainty estimates, Atmos. Chem. Phys., 17(13), 8313-8341, doi:10.5194/acp-17-8313-2017. Each file name is encoded with the site, year, revision number and date, as follows: For all sites, all file names follow this naming scheme: [site]-[year]-[gas]-[measurement height]-[averaging-interval]-[revision date].csv Example: ARL-2016-co2-100m-1-hour-20160504.csv Column Headers (with description) for observation CO2 files: datetime_UTC (date, dd-mm-yyyy HH:MM:SS) dec_year_UTC (decimal year) yyyy (year) mm (month) dd (day) HH (hour, UTC) co2_ppm (dry air mole fraction, ppm, averaged over the hour following the time stamp) co2_SD (standard deviation of air data in 1 hour) co2_n_minutes (number of 1-minute values in each 1-hour average) co2_min (ppm, minimum 1-min value in each 1-hour) co2_max (ppm, maximum 1-min value in each 1-hour) co2_uncertainty (ppm, 1-sigma measurement uncertainty) co2_flags (data quality flag: "..P" indicates preliminary data, which might change if a final calibration is applied at a later date)

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.

This dataset accompanies the publication below. Here we provide the results of the analysis, including gridded estimates of methane emissions for the Washington/Baltimore area at 0.01 degrees resolution and monthly from 2017 through 2021. All files available for unrestricted public use with citation of this data set *except* the Observations_XX files. Observations are for non-commercial use only, as they are purchased from a private data provider (AEM, Inc. via Earth Networks, Inc.).Methane Emissions Show Recent Decline but Strong Seasonality in Two US Northeastern CitiesAnna Karion, Subhomoy Ghosh, Israel Lopez-Coto, Kimberly Mueller, Sharon Gourdji, Joseph Pitt, and James WhetstoneEnvironmental Science & Technology 2023 57 (48), 19565-19574 DOI: 10.1021/acs.est.3c05050

This dataset accompanies the publication below. Here we provide the results of the analysis, including gridded estimates of methane emissions for the Washington/Baltimore area at 0.01 degrees resolution and monthly from 2017 through 2021. All files available for unrestricted public use with citation of this data set *except* the Observations_XX files. Observations are for non-commercial use only, as they are purchased from a private data provider (AEM, Inc. via Earth Networks, Inc.).Methane Emissions Show Recent Decline but Strong Seasonality in Two US Northeastern CitiesAnna Karion, Subhomoy Ghosh, Israel Lopez-Coto, Kimberly Mueller, Sharon Gourdji, Joseph Pitt, and James WhetstoneEnvironmental Science & Technology 2023 57 (48), 19565-19574 DOI: 10.1021/acs.est.3c05050

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