Documentation Revision Date: 2019-03-28
Dataset Version: 1.1
ACT-America's objectives are to study the transport and fluxes of atmospheric CO2 and CH4. At times they flew directly under Orbiting Carbon Observatory-2 (OCO-2) overpasses to evaluate the ability of OCO-2 to observe high-resolution atmospheric CO2 variations.
There are a total of 312 files in this dataset. There are 156 data files in NetCDF (*.nc) file format and 156 data files in ICARTT (*.ict) file format. Note that files in both formats contain the same atmospheric gas concentration data but the ICARTT files contain no aircraft navigation and meteorological data.
This dataset currently includes results from the Summer 2016, Winter 2017, Fall 2017, and Spring 2018 campaigns. New and updated data will be added as it becomes available.
Sweeney, C., B. Baier, J.B. Miller, P. Lang, B. Miller, S. Lehman, S. Englund-Michel, and M.M. Yang. 2018. ACT-America: L2 In Situ Atmospheric Gas Concentrations from Flasks, Eastern USA. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1575
Table of Contents
- Dataset Overview
- Data Characteristics
- Application and Derivation
- Quality Assessment
- Data Acquisition, Materials, and Methods
- Data Access
- Dataset Revisions
This dataset provides atmospheric carbon dioxide (CO2), methane (CH4), carbon monoxide (CO), molecular hydrogen (H2), nitrous oxide (N2O), sulfur hexafluoride (SF6), and other trace gas mole fractions (i.e. "concentrations") from airborne campaigns over North America for the NASA Atmospheric Carbon and Transport - America (ACT-America) project. ACT-America's mission spans five years and includes five six-week field campaigns covering all four seasons and three regions of the central and eastern United States. Two instrumented aircraft platforms, the NASA Langley Beechcraft B200 King Air and the NASA Goddard Space Flight Center's C-130 Hercules, are used to collect high-quality in situ measurements across a variety of continental surfaces and atmospheric conditions. The data were derived from laboratory measurements of whole air samples collected by Programmable Flask Packages (PFP) onboard the two ACT-America aircraft.
The ACT-America, or Atmospheric Carbon and Transport - America, project is a NASA Earth Venture Suborbital-2 mission to study the transport and fluxes of atmospheric carbon dioxide and methane across three regions in the eastern United States. Each flight campaign will measure how weather systems transport these greenhouse gases. Ground-based measurements of greenhouse gases were also-collected. Better estimates of greenhouse gas sources and sinks are needed for climate management and for prediction of future climate.
Spatial Coverage: Flights over eastern and central United States
Spatial Resolution: Point measurements
Temporal Coverage: Periodic flights took place during each intensive campaign.
|Campaign||Beginning and ending dates|
|Summer 2016||2016-07-11 to 2016-08-28|
|Winter 2017||2017-01-21 to 2017-03-10|
|Fall 2017||2017-10-03 to 2017-11-13|
|Spring 2018||2018-04-12 to 2018-05-20|
Temporal Resolution: Approximately 10-12 flask samples were captured during each flight.
Study Area: (These coordinates are the approximate locations of the study sites and may not match the extent of the data files. All latitude and longitude are given in decimal degrees.)
|Site||Northern Extent||Southern Extent||Western Extent||Eastern Extent|
|Central and Eastern United States||49.108||27.230||-106.494||-73.399|
There are 156 data files in netCDF (*.nc) version 4 format following CF conventions 1.6. NetCDF files are structured as GeoTrajectory files, where the observations for a flight segment are connected along a one-dimensional track in space, with time increasing monotonically along the track. These files contain gas concentrations and data from the respective aircraft’s flight navigation system. The flight and altitude data were imported from the ACT-America P3-B Data System (for B200 flights) and Housekeeping data (for C130 flights).
There are 156 data files in the ICARTT file format (*.ict). ICARTT files have detailed header information and follow the standards established and summarized in the ICARTT File Format Standards V1.1. https://www-air.larc.nasa.gov/missions/etc/IcarttDataFormat.htm. The files contain the same atmospheric gas concentration data as the NetCDF files, without the additional navigational or meteorological information.
Naming conventions are the same for both file formats. Files are organized by instrument and aircraft for the flight(s) on a given date.
ACT-America file naming convention
File names are standardized by:
aircraft = either 'B200' or 'C130'
YYYYMMDD = flight date in UTC time
R# = revision number of data. A higher number indicates a more recent revision; e.g. R1 = revision 1
L# = optional launch number. Some flights had more than one segment or launch; e.g. L1 = launch 1
ext = file extension. either '.nc' for NetCDF or '.ict' for ICARTT
Additional information on the aircraft platforms deployed by ACT-America is provided in the accompanying files: Platform_B200.pdf, and Platform_C130.pdf.
Gas variables present in both ICARTT and netCDF files:
|CHLF_MoleFraction_PFP||Chloroform mole fraction||ppt|
|BRFM_MoleFraction_PFP||BRFM mole fraction||ppt|
|C2H6_CAMS2||Ethane mole fraction||ppt|
|CCl4_MoleFraction_PFP||CCI4 mole fraction||ppt|
|CS2_MoleFraction_PFP||CS2 mole fraction||ppt|
|F112_MoleFraction_PFP||F112 mole fraction||ppt|
|F124_MoleFraction_PFP||F124 mole fraction||ppt|
|F141B_MoleFraction_PFP||Dichlorofluoroethane mole fraction||ppt|
|HF21_MoleFraction_PFP||HF21 mole fraction||ppt|
|NF3_MoleFraction_PFP||NF3 mole fraction||ppt|
|SF6_MoleFraction_PFP||Sulfur Hexafloride mole fraction||ppt|
|HF22_MoleFraction_PFP||HF22 mole fraction||ppt|
|nC6H14_MoleFraction_PFP||n-Hexane mole fraction||ppt|
|PCE_MoleFraction_PFP||Perchloroethylene mole fraction||ppt|
|SF6_CCGG_MoleFraction_PFP||Sulfur Hexafloride mole fraction||ppt|
|BENZ_MoleFraction_PFP||Benzene mole fraction||ppt|
|C2F6_MoleFraction_PFP||Hexafluorethane mole fraction||ppt|
|C2H2_MoleFraction_PFP||Acetylene mole fraction||ppt|
|C2H6_MoleFraction_PFP||Ethane mole fraction||ppt|
|C3H8_MoleFraction_PFP||Propane mole fraction||ppt|
|CF4_MoleFraction_PFP||Carbon Tetrafloride mole fraction||ppt|
|CH2BrCl_MoleFraction_PFP||Bromochloromethane mole fraction||ppt|
|CH3I_MoleFraction_PFP||Methyl Iodide mole fraction||ppt|
|CH4_MoleFraction_PFP||Methane mole fraction||ppb|
|CH4C13_PFP||C-13 of CH4||permil|
|CO_MoleFraction_PFP||Carbon Monoxide mole fraction||ppb|
|CO2_MoleFraction_PFP||Carbon Dioxide mole fraction||ppm|
|DIBR_MoleFraction_PFP||Dibromomethane mole fraction||ppt|
|DICL_MoleFraction_PFP||Dimethyl Chloride mole fraction||ppt|
|F113_MoleFraction_PFP||F113 mole fraction||ppt|
|F115_MoleFraction_PFP||F115 mole fraction||ppt|
|F11B_MoleFraction_PFP||F11 mole fraction||ppt|
|F125_MoleFraction_PFP||Pentafluoroethane mole fraction||ppt|
|F13_MoleFraction_PFP||F13 mole fraction||ppt|
|F134A_MoleFraction_PFP||Tetrafluoroethane mole fraction||ppt|
|F143a_MoleFraction_PFP||1-1-1-Trifluoroethane mole fraction||ppt|
|F152A_MoleFraction_PFP||1-1-Difluoroethane mole fraction||ppt|
|F227e_MoleFraction_PFP||F227 mole fraction||ppt|
|F23_MoleFraction_PFP||Fluoroform mole fraction||ppt|
|F236fa_MoleFraction_PFP||F236fa mole fraction||ppt|
|F32_MoleFraction_PFP||F32 mole fraction||ppt|
|F365m_MoleFraction_PFP||Pentafluorobutane mole fraction||ppt|
|FC12_MoleFraction_PFP||FC12 mole fraction||ppt|
|H1211_MoleFraction_PFP||Halon 1211 mole fraction||ppt|
|H1301_MoleFraction_PFP||Halon 1301 mole fraction||ppt|
|H2_MoleFraction_PFP||Hydrogen mole fraction||ppb|
|H2402_MoleFraction_PFP||Halon 2402 mole fraction||ppt|
|HF133a_MoleFraction_PFP||HF133a mole fraction||ppt|
|iC4H10_MoleFraction_PFP||isoButane mole fraction||ppt|
|iC5H12_MoleFraction_PFP||isoPentane mole fraction||ppt|
|MCFA_MoleFraction_PFP||MCFA mole fraction||ppt|
|MEBR_MoleFraction_PFP||Methyl Bromide mole fraction||ppt|
|MECL_MoleFraction_PFP||Methyl Chloride mole fraction||ppt|
|N2O_MoleFraction_PFP||Nitrous Oxide mole fraction||ppb|
|nC4H10_MoleFraction_PFP||neoButane mole fraction||ppt|
|nC5H12_MoleFraction_PFP||neoPentane mole fraction||ppt|
|OCS_MoleFraction_PFP||Carbonyl Sulfide mole fraction||ppt|
|P218_MoleFraction_PFP||P218 mole fraction||ppt|
|SO2F2_MoleFraction_PFP||Sulfuryl Fluoride mole fraction||ppt|
|TCE_MoleFraction_PFP||Trichloroethylene mole fraction||ppt|
|TOL_MoleFraction_PFP||Toluene mole fraction||ppt|
Navigation and Meteorological variables only present in netCDF files:
|Flight_ID||Flight identification (aircraft and flight date)|
|Aircraft_Sun_Azimuth||Platform azimuth angle||degree|
|Aircraft_Sun_Elevation||Solar elevation angle||degree|
|Cabin_Pressure||Air pressure of cabin||mb|
|Day_of_Year||Day of year||day starting Jan 1 UTC|
|Dew_Point||Dew point temperature||Celcius|
|GPS_Altitude||Global Positioning System altitude||meters|
|GPS_Time||Time||hours since 2016-01-01 00:00:00.0 UTC|
|Ground_Speed||Platform speed with respect to ground||meters per second|
|Indicated_Air_Speed||Indicated air speed||kts|
|Mixing_Ratio||H2O mixing ratio||g per kg|
|Part_Press_Water_Vapor||Water vapor partial pressure in air||mb|
|Pitch_Angle||Platform pitch angle||degree|
|Roll_Angle||Platform roll angle||degree|
|Sat_Vapor_Press_H2O||H2O saturation vapor pressure of water||mb|
|Sat_Vapor_Press_Ice||H2O saturation vapor pressure of ice||mb|
|Solar_Zenith_Angle||Solar zenith angle||degree|
|Static_Air_Temp||Static air temperature||Celcius|
|Sun_Azimuth||Solar azimuth angle||degree|
|Total_Air_Temp||Total air temperature||Celcius|
|True_Air_Speed||Platform speed with respect to air||kts|
|True_Heading||Platform yaw angle||degree|
|Vertical_Speed||Vertical speed||ft per minute|
|Wind_Speed||Wind speed||m per second|
|Altitude_AGL_m||Aircraft altitude above ground level||m|
|Ground_Elevation_m||Ground elevation above mean sea level||m|
Application and Derivation
ACT-America, or Atmospheric Carbon and Transport – America, will conduct five airborne campaigns across three regions in the eastern United States to study the transport of atmospheric carbon. The eastern half of the United States is a region that includes a highly productive biosphere, vigorous agricultural activity, extensive gas and oil extraction and consumption, dynamic, seasonally varying weather patterns and the most extensive carbon cycle and meteorological observing networks on Earth, serves as an ideal setting for the mission.
Each 6-week campaign will accurately and precisely quantify anomalies in atmospheric carbon, also known as carbon flux. Accurate carbon flux data is necessary to address all terrestrial carbon cycle science questions. ACT-America addresses the three primary sources of uncertainty in atmospheric inversions — transport error, prior flux uncertainty and limited data density.
ACT-America will advance society’s ability to predict and manage future climate change by enabling policy-relevant quantification of the carbon cycle. Sources and sinks of atmospheric carbon dioxide (CO2) and methane (CH4) are poorly known at regional to continental scales. ACT-America will enable and demonstrate a new generation of atmospheric inversion systems for quantifying CO2 and CH4 sources and sinks.
Figure 2. A schematic showing ACT-America project goals.
- To quantify and reduce atmospheric transport uncertainties.
- To improve regional-scale, seasonal prior estimate of CO2 and CH4 fluxes.
- To evaluate the sensitivity of Orbiting Carbon Observatory (OCO-2) column measurements to regional variability in tropospheric CO2.
ACT-America will achieve these goals by deploying airborne and ground-based platforms to obtain data that will be combined with data from existing measurement networks and integrated with an ensemble of atmospheric inversion systems. Aircraft instrumented with remote and in situ sensors will observe how mid-latitude weather systems interact with CO2 and CH4 sources and sinks to create atmospheric CO2/CH4 distributions. A model ensemble consisting of a mesoscale atmospheric transport model with multiple physics and resolutions options nested within global inversion models and surface CO2/CH4 flux ensembles will be used to predict atmospheric CO2 and CH4 distributions.
Beyond the conclusion of the mission, application of the knowledge gained from this mission will improve diagnoses of the carbon cycle across the globe for decades.
Within the data, nodata and out-of-range values are provided in the dataset as described. Instrument precision specifications are available in the ACT-America proposal and replicated below (Fig 3.)
Figure 3. Instrument precision table as provided in the ACT-America proposal.
See additional instrument quality control discussion here: https://www.esrl.noaa.gov/gmd/ccgg/aircraft/qc.html
Data Acquisition, Materials, and Methods
The eastern half of the United States, a region that includes a highly productive biosphere, vigorous agricultural activity, extensive gas and oil extraction, dynamic, seasonally varying weather patterns and the most extensive carbon cycle and meteorological observing networks on Earth, serves as an ideal setting for the mission. Flights will concentrate observations on three study domains: Northeast, South-central, and Midwest.
ACT-America will deploy the NASA C-130 and B-200 aircraft to measure atmospheric CO2 and CH4 in the atmospheric boundary layer (ABL) and free troposphere (FT). The mission proposes a total of 70 science flights, 528 hours for the C-130 and 396 hours for the B-200, dedicated in a roughly 3:3:1 ratio among fair weather, stormy weather, and OCO-2 underpass flight patterns.
For fair and stormy weather flights, the C-130 will fly at 3-8 km above ground, collecting in situ measurements in the lower FT, remotely sensed, column-averaged CO2 measurements focused on the ABL, and occasional in situ vertical profiles. The B-200 will primarily sample the ABL. For OCO-2 underflights, the C-130 will fly at 8 km above ground with the B-200 flying in the ABL, both along the OCO-2 flight track. The existing in situ tower CO2/CH4 observing network will be enhanced with five additional tower sites.
The mission will deliver 2-3 times more high-quality lower tropospheric CO2 and CH4 observations than any previous airborne campaign.
Data from the fair-weather flights are intended to quantify regional CO2 and CH4 fluxes, and to evaluate fair weather atmospheric C transport processes. The flight pattern is designed to provide extensive sampling of the ABL and lower FT in source/sink regions, meeting the requirements for the fair weather investigation. The C-130 aircraft will fly a U-shape pattern with flight legs perpendicular to the wind, sampling FT and ABL properties downwind of the sources and sinks of C. The C-130 will fly at roughly two times the midday ABL depth, (~3-4 km above ground level (AGL)) with periodic descents and ascents (5 to 10 times in a 6-8-hr flight) to sample the ABL. Although clear sky conditions will be targeted, the C-130 will conduct more profiling if low-altitude clouds interfere with the remote sensors. The B-200 aircraft will partake in two flights per day and will sample a subset of the C-130 flight path focusing on long transects in the ABL with periodic ascents to the FT. The two aircraft will operate over the same time period, but precise coordination is not required.
Data from stormy-weather flights will be used in combination with the data from fair-weather flights to evaluate the transport of C in the mid-latitudes. The flight plans include flight legs parallel to and crossing frontal boundaries at two or more altitudes, and crossing the frontal zone at two or more locations, meeting the requirements for the stormy weather investigation.
The pattern for the OCO-2 inter-comparison flights is designed to obtain data to evaluate the degree to which OCO-2 column CO2 measurements capture true spatial variability in column CO2 content over the continents. Two OCO-2 under flights will be conducted during each campaign and will be selected to cover varying surface reflectance, topography, and aerosol and cloud cover, all possible sources of bias in the OCO-2 measurements. The C-130 flights will be 1000 km in length and flown at 8 km (28 kft) altitude to maximize the fraction of the atmospheric column sampled by the MFLL. The B-200 aircraft will sample a shorter (~360 km) leg in the ABL, often the largest source of variability in column CO2. The B-200 flight will be centered with the C-130 and both aircraft will be vertically stacked during the OCO-2 overpass.
ACT-America deployed high-quality, field-tested trace gas and meteorological instruments. This dataset includes measurements from discrete air samples captured by the flask sampling system onboard the aircraft. The two air-sampling devices, the Programmable Flask Package (PFP) and Programmable Compressor Package (PCP) systems, are used routinely on aircraft as part of the NOAA/ESRL Greenhouse Gas Reference network (Sweeney et al., 2015).
Flask air sampling system
Figure 4. Flask sampling system for aircraft measurements. Left: Programmable Flash Package (PFP) containing 12 flasks. Right: Programmable Compressor Package (PCP) containing pumps for pressurizing the flasks. (Image courtesy: http://www.esrl.noaa.gov/gmd/ccgg/aircraft/sampling.html)
A typical sampling routine uses one PCP and one or more PFP(s) that are pre-programmed with a flight-specific sampling plan of target altitudes for each sample. Sampling is timed to coincide with the overflight of a ground site of interest, or when interesting geophysical conditions are encountered. A map of flask sample locations is depicted in Figure 1. The PCP is connected to an LED display that communicates target sampling altitudes to the pilot. The pilot maintains the aircraft at a consistent altitude for the duration of each sample collection, typically under 40 seconds. For each sample, the inlet line and compression manifold are flushed with about 5 liters of ambient air. Valves on both ends of the current flask are then opened and the flask is flushed with about 10 more liters of ambient air to displace the dry, low CO2 fill gas with which the flasks are shipped. The sample flush air is measured by a mass flow meter to ensure that a sufficient volume passes through the manifold and flask before the downstream valve is closed and pressurization begins. Sample flush volumes and fill pressures during sampling are recorded by the data logger, along with ambient temperature, pressure, and relative humidity. GPS position and time stamp are also recorded with each sample.
These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).
Contact for Data Center Access Information:
- E-mail: email@example.com
- Telephone: +1 (865) 241-3952
ICARTT files have detailed header information and follow the standards established and summarized in the ICARTT File Format Standards V1.1. https://www-air.larc.nasa.gov/missions/etc/IcarttDataFormat.htm
Sweeney et al., 2015: Seasonal Climatology of CO2 across North America from aircraft measurements in the NOAA/ESRL Global Greenhouse Gas Reference Network, J Geophys Res Atmos, 120, 5155-5190, https://doi.org/10.1002/2014JD02259
Version 1.1 (released 2019-03-27) updated all PFP data from the Summer 2016 and Winter 2017 campaigns and added the Fall 2017 and Spring 2018 campaign data.
Version 1.0 (released 2018-06-26) provided the PFP data from Summer 2016 and Winter 2017 campaigns.