//////////////////////////////////////////////////////////////////////////////////////// README for Site Averages Dataset File Name: es9b07148_SI_002.txt Revision Date: 2020-02-05 //////////////////////////////////////////////////////////////////////////////////////// Dataset Summary All facilities are in the Gulf of Mexico off the coasts of Louisiana and Texas. Data were acquired between February 12th, 2018 and February 22nd, 2018. This summary dataset gives site average emissions as worked up via Gaussian plume analysis. Results are included in the comma-separated-value file. An arbitrary site identifying number (ARI ID) is listed. Errors are reported for CH4 emissions at the 95% confidence level. Errors on emission signatures (tracer ratios and δ’s) are reported at the 1-σ level. Modified combustion efficiency (MCE) is calculated based solely on the CO/CO2 ratio. The latitude, longitude and height of the simulated emission plumes (sim height) is noted. Starting with the column named "Structure Name", data has been collected from BOEM data sources, and matched to the geographic location of the measured platforms. The 1Hz measurement data used in this analysis is also available as SI. For intermediate analysis results including individual plume characteristics, please contact the corresponding author at tyacovitch@aerodyne.com //////////////////////////////////////////////////////////////////////////////////////// Data Disclaimer The authors reserve the right to make corrections to this data based on scientifically justified reasons. Please report any problems with this dataset to the corresponding author (tyacovitch@aerodyne.com). Please abide by the Fair Use statement and cite this dataset appropriately. //////////////////////////////////////////////////////////////////////////////////////// Column descriptions ariID Arbitrary site identifier Count number of plume measurements used in the determination of the methane emission estimate Emission CH4 (kg/Hr) Average methane emission rate, in kilogram of methane per hour. 1 sigma error (kg/hr) For those sites with multiple downwind transects (3 or more), the standard deviation of the Gaussian quantifications is reported. LL (kg/hr at 95% conf) Lower limit for the methane emission rate, expressed as the 95% confidence interval. UL (kg/hr at 95% conf) Upper limit for the methane emission rate, expressed as the 95% confidence interval. C2H6/CH4 (ppb/ppb) Ethane to methane ratio, in parts-per-bilion per parts-per-billion 1 sigma error on C2H6/CH4 Error in the ethane to methane ratio, expressed as 1 sigma. CO/CO2 (ppb/ppm) Carbon monoxide to carbon dioxide ratio, in parts-per-billion per parts-per-million 1 sigma error on CO/CO2 Error in the carbon monoxide to carbon dioxide ratio, expressed as 1 sigma MCE Modified combustion efficiency, computed using CO and CO2 content of the plume using the formula MCE = 1/{1+(CO/CO2 ratio in ppb/ppm)/1000} del 13C (per mil) Isotopic signature of carbon-13 methane in the plume, expressed in per-mil 1 sigma error on del 13C (per mil) Error on the del 13C isotopic composition, expressed as 1 sigma del D (per mil) Isotopic signature of deuterated methane (CH3D) in the plume, expressed in per-mil 1 sigma error on del D (per mil) Error on the del D isotopic composition, expressed as 1 sigma Lat Latitude of the offshore platform, in decimal degrees Lon Longitude of the offshore platform, in decimal degrees First Time Time of first plume encounter, in universal coordinated time Last Time Time of last plume encounter, in universal coordinated time Sim Height (m) Emission source height used in the gaussian plume simulation, in meters. A value of 15.24 m is used when no other height data about a platform was found. Avg Dist Downwind (m) Average distance downwind for the plume measurements. The sampling plan aimed to sample sites at multiple distances when possible. Avg Plume width ratio (meas/expected) Average ratio of the measured 1-sigma plume width (Sy meas) to the expected plume width (Sy expected) based on the nearest Pasquill Stability class. Uncertain location? Flag indicating whether the measurement location was uncertain. See text of paper and SI. Null? Flag indicating that no emissions were detected from this site. Water Depth (m) Water depth as indicated in the BOEM database. Analyst Note Analysis note, including reasons for an "uncertain" location, and indicating sites that include multiple individual platform structures. Planned (0), Post-Analysis (0.5) or Fortuitous (1) Flag indicating whether the site measurement was planned prior to the campaign, fortuitous (added-on during the campaign) or post-analysis (found in the data post-campaign). Structure Name The name of the structure as given by its owner. This column and the other columns below are from the BOEM database Field A labeled area consisting of one or more reservoirs on the same geologic structural feature. More information on fields and leases can be found here: https://www.boem.gov/sites/default/files/documents/newsroom/Operations-Field-Directory.pdf Complex ID (or State Oil Lease/Gas ID) A unique identifier for a single man-made structure or a group of structures connected by a walkway Lease Also known as "lease block". A subdivision of a field. Labeled "Authority Number" in the BOEM database, with the description: the unique identifier which was applied against a particular platform structure. https://metadata.boem.gov/geospatial/OCSplatforms-GOMR-NAD27.xml Type Type of structure. Possible types are: Caisson Compliant tower Fixed Leg Platform Floating production, storage and offloading Mobile Production Unit Mini Tension Leg Platform Semi Submersible (Column Stabilized Unit) Floating Production System SPAR Platform floating production system Fixed anchors or mooring piles used to secure a structure to the seafloor Subsea Manifold Subsea templates Tension leg platform Underwater completion or subsea caisson Well Protector