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ACT-America: L2 In Situ CO2, CO, and CH4 Concentrations from Towers, Eastern USA

Documentation Revision Date: 2018-02-05

Data Set Version: 1

Summary

This dataset provides atmospheric carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) concentrations as measured on a network of 9 instrumented communications towers operated by the Atmospheric Carbon and Transport-America (ACT-America) project. ACT-America's mission spans five years and includes five 6-week intensive field campaigns covering all 4 seasons and 3 regions of the central and eastern United States. Tower-based measurements began in early 2016 and are continuously collecting CO2, CO, and CH4 data to characterize ground-level (>100 m) carbon background conditions to support the periodic airborne measurement campaigns and transport modeling conducted by ACT-America. The towers are instrumented with infrared cavity ring-down spectrometer systems (CRDS; Picarro Inc.). Data are reported for the highest sampling port on each tower, with heights ranging between 61 and 215 meters above ground level. The data averaging interval is 1 hour for 8 towers and 10 minutes for the Marcellus South - Mildred tower. The averaging interval standard deviation and uncertainty derived from periodic flask sample to in-situ measurement comparisons are provided. Complete tower location, elevation, instrument height, and date/time information are also provided.

This dataset provides results from year 2016. New annual tower measurement data will be added approximately 6 months after the end of each year.

There are a total of 18 files in this dataset. The data from the 9 towers are provided in two formats; ICARTT file format (*.ict) and netCDF (*.nc) CF-compliant station-based time series file format.  

Figure 1: Locations of ACT-America towers active in 2016.

Citation

Miles, N.L., S.J. Richardson, D.K. Martins, K.J. Davis, T. Lauvaux, B.J. Haupt, and S.K. Miller. 2018. ACT-America: L2 In Situ CO2, CO, and CH4 Concentrations from Towers, Eastern USA. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1568

Table of Contents

  1. Data Set Overview
  2. Data Characteristics
  3. Application and Derivation
  4. Quality Assessment
  5. Data Acquisition, Materials, and Methods
  6. Data Access
  7. References

Data Set Overview

This dataset provides atmospheric carbon dioxide (CO2), carbon monoxide (CO), and methane (CH4) concentrations as measured on a network of 9 instrumented communications towers operated by the Atmospheric Carbon and Transport-America (ACT-America) project. ACT-America's mission spans five years and includes five 6-week intensive field campaigns covering all 4 seasons and 3 regions of the central and eastern United States. Tower-based measurements began in early 2016 and are continuously collecting CO2, CO, and CH4 data to characterize ground-level (>100 m) carbon background conditions to support the periodic airborne measurement campaigns and transport modeling conducted by ACT-America. The towers are instrumented with infrared cavity ring-down spectrometer systems (CRDS; Picarro Inc.). Data are reported for the highest sampling port on each tower, with heights ranging between 61 and 215 meters above ground level. The data averaging interval is 1 hour for 8 towers and 10 minutes for the Marcellus South - Mildred tower. The averaging interval standard deviation and uncertainty derived from periodic flask sample to in-situ measurement comparisons are provided. Complete tower location, elevation, instrument height, and date/time information are also provided.

This dataset provides results from year 2016. New annual tower measurement data will be added approximately 6 months after the end of each year.

Project:  Atmospheric Carbon and Transport (ACT-America)

ACT-America is an Earth Venture Suborbital-2 mission that will conduct five airborne campaigns across three regions in the eastern United States to study the transport and fluxes of atmospheric carbon dioxide and methane. Each 6-week campaign will measure how weather systems transport these greenhouse gases. The objective of the study is to enable more accurate and precise estimates of the sources and sinks of these gases. Better estimates of greenhouse gas sources and sinks are needed for climate management and for prediction of future climate. ACT America addresses three primary sources of uncertainty in our ability to infer carbon dioxide and methane sources and sinks - transport error, prior flux uncertainty and limited data density.

Related Data Set:

Digangi, J.P., Y. Choi, J.B. Nowak, and H.S. Halliday. 2017. ACT-America: L2 In Situ Atmospheric CO2, CO, CH4, and O3 Concentrations, Eastern USA. ORNL DAAC, Oak Ridge, Tennessee, USA. https://doi.org/10.3334/ORNLDAAC/1556

Data Characteristics

Spatial Coverage:  Tower locations over eastern and central United States

Spatial Resolution:  Point locations

Temporal Coverage: 2016-01-01 to 2016-12-31

Temporal Resolution: Computed mean within each hour. The Mildred site has an averaging window of 10 minutes instead of 1 hour.

Study Area: (Coordinates in decimal degrees)

Site

Westernmost Longitude

Easternmost Longitude

Northernmost Latitude

Southernmost Latitude

Eastern and Central United States

-92.2829

-76.4188

41.4662

30.1951

 

Tower Locations and Measurement Parameters

Tower Site Latitude Longitude

Elevation (meters ASL)

Sampling Height on Tower (m) Start Date End Date
Panama_City 30.1951 -85.8336 5 100 2016-01-01 2016-12-31
Mooresville 39.5805 -86.4207 256 121 2016-01-01 2016-12-31
Monroe 32.469 -92.2829 65 100 2016-01-01 2016-12-31
Millerville 33.1759 -85.8911 328 100 2016-01-01 2016-12-31
Mildred 41.4662 -76.4188 591 61 2016-01-08 2016-12-31
Magee 31.8869 -89.7276 132 100 2016-01-19 2016-09-16
Grenada 33.7525 -89.8539 105 100 2016-01-08 2016-07-10
Greenfield 39.8627 -85.7448 277 130 2016-01-01 2016-12-31
Danville 36.70581 -79.4369 276 215 2016-07-13 2016-12-31

 

Data File Information:

There are 9 data files in netCDF (*.nc) time series (station) file format following CF conventions 1.6. Each tower location is contained in a separate file. These files contain greenhouse gases (CO2, CH4 and CO) as dry mole fractions averaged over each hour. However, the Mildred site has an averaging window of 10 minutes instead of one hour. The standard deviation within the averaging window and an uncertainty estimate are also provided.

There are 9 data files in ICARTT file format (*.ict) following ICARTT standards. All ICARTT files have detailed header information and follow the standards established and summarized in the ICARTT File Format Standards V1.1. 

Both the netCDF and ICARTT formatted files contain the same greenhouse gas dry mole fraction data.

 

File naming convention

Naming conventions are the same for both file formats. ACT-America files names are standardized by:

project-instrument_platform-station_startdate_R#_thruenddate.ext

where:

project = ACTAMERICA

instrument = PICARRO

platform = Ground

station = one of the 9 tower site names listed above

startdate = start date in UTC, in YYYYMMDD format

R# = revision number of data. A higher number indicates a more recent revision.

enddate = YYYYMMDD

ext = file extension, either '.nc' for NetCDF or '.ict' for ICARTT

An example file name:

ACTAMERICA-PICARRO_Ground-Danville_20160713_R0_thru20161231.ict
 

Data Dictionary (Note that the Mildred Tower files contain additional measurement and descriptor fields.)

Variable Name Description Units
Station Information    
altitude height above ground level m
elevation height above sea level m
latitude site latitude decimal degrees north
longitude site longitude decimal degrees east
site_name site name  
Time Series Variables    
C2H6 *** dry C2H6 mixing ratio average between Time_start and Time_stop in parts per billion by volume ppbv
CH4 dry CH4 mixing ratio average between Time_start and Time_stop in parts per billion by volume ppbv
CH4_std dry CH4 mixing ratio standard deviation between Time_start and Time_stop in parts per billion by volume ppbv
CH4_unc estimated CH4 measurement uncertainty in parts per billion by volume ppbv
CH4_IsotopicRatio *** isotopic ratio (13C/12C) of CH4 in permil per mil
CO dry CO mixing ratio average between Time_start and Time_stop in parts per billion by volume ppbv
CO_std dry CO mixing ratio standard deviation between Time_start and Time_stop in parts per billion by volume ppbv
CO_unc estimated CO measurement uncertainty in parts per billion by volume ppbv
CO2 dry CO2 mixing ratio average between Time_start and Time_stop in parts per million by volume ppmv
CO2_std dry CO2 mixing ratio standard deviation between Time_start and Time_stop in parts per million by volume ppmv
CO2_unc estimated CO2 measurement uncertainty in parts per million by volume ppmv
Data_Flag data quality indicator 1 indicates no known problems. 0 indicates that the data is not recommended for use.
DOY day of year of the measurement day of year
H20 ** water vapor mixing ratio average of the dried sample between Time_start and Time_stop in parts per hundred by volume. Samples are dried, H2O useful only for diagnostic purposes. %
Hour nominal hour of the measurement hour
Instrument_Flag ** indicator of the instrument used to make the measurement 0 = CFKADS2005, 1 = CFKADS2025, 2 = CFKADS2218
N_points *** number of points included in average  
time * time hours since 2016-01-01 00:00:00.0 UTC
Time_mid average fractional day of year of the measurement fractional day of year UTC
Time_start minimum fractional day of year of the measurement fractional day of year UTC
Time_stop maximum fractional day of year of the measurement fractional day of year UTC
Year year of the measurement year
Out of Range or Missing    
ulod_flag Data greater than the upper limit of detection -7777
llod_flag Data less than the upper limit of detection -8888
Missing data, nodata, or _FillValue   -9999

* only present in netCDF file dimension and variable

** Not available in all files

*** Only available in the ACTAMERICA-PICARRO_Ground-Mildred_20160108_R0_thru20161231 files

Application and Derivation

ACT-America's goals include:

  1. To quantify and reduce atmospheric transport uncertainties.
  2. To improve regional-scale, seasonal prior estimate of CO2 and CH4 fluxes.
  3. 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.

The ACT-America mission requires both airborne and ground measurements, including 1) remote measurements of column CO2 number densities from various altitudes and meteorological conditions, 2) in situ measurements of CO2, CH4, trace gases and meteorological variables in the Atmospheric Boundary Layer (ABL) and free troposphere (FT), and 3) in situ measurements of CO2, CH4, and H2O collected 100 m above ground level (AGL) or higher from towers.

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.

Quality Assessment

Calibration: Prior to deployment, the instruments were calibrated in the laboratory using 4 NOAA-calibrated tanks.  A field calibration tank was sampled daily and used to apply a zero-offset correction. Round robin tests using 3-4 NOAA-calibrated tanks were conducted every 1-2 years. NOAA flask measurements were used for comparison at the Mildred, Greenfield, and Mooresville sites.

Uncertainty: The averaging interval standard deviation and uncertainty derived from periodic flask sample to in-situ measurement comparisons are provided in the data files. Based on flask to in-situ comparisons and round robin testing presented in Richardson et al. (2017), the estimated compatibility of these measurements is approximately 0.18 ppm CO2 and 0.6 ppb CH4.  

Data Acquisition, Materials, and Methods

Tower Sites

ACT-America will utilize existing communications towers, filling gaps that exist in or near our three study regions in existing tower networks. Specific sites have been selected in science-critical locations based on tall tower and local Ethernet or cell phone data connection availability. Daily, automated data transfer to the Langley Atmospheric Science Data Center allows for remote monitoring of instrument status and investigation planning.

Tower platforms utilize the Picarro G2301 CRDS for CO2, CO, CH4, and H2O measurements. Instruments report raw data every 2 - 3 seconds, but these data points are not independent because of the mixing volume. Excluding data from the calibration tanks and other measurement heights (if applicable), the mean within each hour was computed. The minimum and maximum times of the data included in each average is indicated in the file.

Data Synthesis

Additional measurements that will be used in this study include NOAA moorings along the East and Gulf coasts, the Total Carbon Column Observing Network (TCCON) sites at Park Falls, Wisconsin (WLEF) and the Department of Energy-Atmospheric Radiation Measurement (DOE-ARM) Central Facility, OK sites, and the NOAA Aircraft (biweekly vertical profiles) and Tall Tower networks. These data are all accessible to the public.

Data Access

These data are available through the Oak Ridge National Laboratory (ORNL) Distributed Active Archive Center (DAAC).

ACT-America: L2 In Situ CO2, CO, and CH4 Concentrations from Towers, Eastern USA

Contact for Data Center Access Information:

References

ICARTT File Format Standards V1.1. Available from https://www-air.larc.nasa.gov/missions/etc/IcarttDataFormat.htm

Miles, N.L., D.K. Martins, S.J. Richardson, C. Rella, T. Lauvaux, K.J. Davis, Z.R. Barkley, K. McKain, and C. Sweeney. 2017. Calibration and field testing of cavity ring-down laser spectrometers measuring CH4, CO2, and δ13CH4 deployed on towers in the Marcellus Shale region. Atmos. Meas. Tech. Disc., in review, https://doi.org/10.5194/amt-2017-364

Miles, N.L., S.J. Richardson, T. Lauvaux, K.J. Davis, J. Turnbull, A. Karion, C. Sweeney, K.R. Gurney, R. Patarasuk, I. Razlivanov, M.O. Cambaliza, and P. Shepson. 2017. Quantification of urban atmospheric boundary layer greenhouse gas dry mole fraction enhancements: Results from the Indianapolis Flux Experiment (INFLUX). Elem. Sci. Anth., 5:27,  http://doi.org/10.1525/elementa.127

Richardson SJ, Miles NL, Davis KJ, Lauvaux T, Martins DK, Turnbull JC, et al.. 2017. Tower measurement network of in-situ CO2, CH4, and CO in support of the Indianapolis FLUX (INFLUX) Experiment. Elem Sci Anth. 5:59. DOI: http://doi.org/10.1525/elementa.140