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CARVE: L2 Atmospheric Gas Concentrations, Tower-based Flasks, Alaska, 2012-2015

Documentation Revision Date: 2016-11-14

Data Set Version: 1

Summary

This data set provides atmospheric carbon dioxide, methane, carbon monoxide, molecular hydrogen, nitrous oxide, sulfur hexafluoride, and other trace gas mole fractions (i.e. "concentrations") from a flask sampling system at the CARVE flux tower in Fox, Alaska for the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE). The data were derived from laboratory measurements of whole air samples collected by a Programmable Flask Package (PFP) from the top of the tower at 32 m above ground level during late evening multiple times per month since January 2012. Whole air samples collected in the PFPs were analyzed on automated systems at the NOAA Earth System Research Laboratory (ESRL) Global Monitoring Division in Boulder, CO, which also analyzes samples from the NOAA/ESRL Global Greenhouse Gas Reference Network. The measurements included in this data set are crucial for understanding changes in Arctic carbon cycling and the potential threats posed by thawing of Arctic permafrost.

There are 4 data files in netCDF (*.nc) format, one for each year of samples collected at the CARVE tower, with this data set.

Figure 1. a) Contours show sensitivity of CO2 and CH4 measurements to boreal forests and lowlands of interior Alaska; b) CARVE tower (Karion et al., 2016)

Citation

Miller, J.B., C. Sweeney, A. Karion, and C.E. Miller. 2016. CARVE: L2 Atmospheric Gas Concentrations, Tower-based Flasks, Alaska, 2012-2015. ORNL DAAC, Oak Ridge, Tennessee, USA. http://dx.doi.org/10.3334/ORNLDAAC/1405

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

Project: Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE)

The Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) is a NASA Earth Ventures (EV-1) investigation designed to quantify correlations between atmospheric and surface state variables for Alaskan terrestrial ecosystems through intensive seasonal aircraft campaigns, ground-based observations, and analysis sustained over a 5-year mission. CARVE collected detailed measurements of greenhouse gases on local to regional scales in the Alaskan Arctic and demonstrated new remote sensing and improved modeling capabilities to quantify Arctic carbon fluxes and carbon cycle-climate processes. CARVE science fills a critical gap in Earth science knowledge and satisfies high priority objectives across NASA’s Carbon Cycle and Ecosystems, Atmospheric Composition, and Climate Variability & Change focus areas as well as the Air Quality and Ecosystems elements of the Applied Sciences program. CARVE data also complements and enhances the science return from current NASA and non-NASA sensors.

Related Data:

A full list of CARVE data products is available at: https://carve.ornl.gov/dataproducts.html

Data Characteristics

Spatial Coverage: CARVE tower near Fairbanks, Alaska

Spatial Resolution: Point measurements

Temporal Coverage: 20120104 - 20151205

Temporal Resolution: Air samples collected multiple times per month

Study Area (coordinates in decimal degrees)

Site

Westernmost Longitude

Easternmost Longitude

Northernmost Latitude

Southernmost Latitude

CARVE tower

-147.5982

-147.5982

64.9863

64.9863

 

Data File Information

All data are stored in NetCDF (*.nc) version 4 file format. Each file provides measurements of dry mole fractions of atmospheric CO2, CH4, CO, H2, N2O, and SF6 and other trace gases acquired over one year of measurements.

 

Table 1: CARVE file naming convention. Example file name: carve_GroundFlask_L2_b23_20111231_20160807222152.nc

Name element

Example value

Units

Project name

carve

 

Instrument

GroundFlask

 

Processing level

L2

 

Build ID

b23

 

Flight date

20111231

yyyymmdd

Processing date and time

20150727184306

yyyymmddhhmmss

 

Data variables

Each file contains 14 geolocation variables and 69 science measurement variables described in (Table 2).

Table 2. Data variables in each netCDF file. Fill value or missing data were set to -999.9 for all variables.

Variable name

Description

Units

Geolocation and ancillary measurements

 

 

center_lat

latitude

degrees North

center_lat_standard_error

latitude standard error

degrees North

center_lon

longitude

degrees East

center_lon_standard_error

longitude standard error

degrees East

height

height of sample above ground

meters

height_standard_error

height standard error

meters

geolocation_qc

geolocation status flag

0 = Success, 1 = Error

time

time

seconds since 1980-1-6 0:0:0

elevation

surface elevation

meters

event_number

NOAA database event number

 

intake_height

sample intake height

meters

flask_id

sample container ID

 

sample_method

sample collection method

 

site_code

sample site code

 

Science measurements

 

 

benz

benzene (C6H6)

parts per trillion (ppt) **

brfm

bromoform (CHBr3)

ppt

c2f6

hexafluoroethane (CF3CF3)

ppt

c2h2

ethyne (acetylene; C2H2)

ppt

c2h4

ethene (ethylene; C2H4)

ppt

c2h6

ethane (C2H6)

ppt

c3h6

propene (propylene; C3H6)

ppt

c3h8

propane (C3H8)

ppt

ccl4

carbon tetrachloride (tetrachloromethane; CCl4)

ppt

cf4

carbon tetraflouride (tetrafluoromethane; CF4)

ppt

ch2brcl

bromochloromethane (CH2BrCl)

ppt

ch3i

methyl iodide (CH3I)

ppt

ch4

methane (CH4)

parts per billion (ppb) **

chlf

chloroform (CHCl3)

ppt

co

carbon monoxide (CO)

ppb

co2

carbon dioxide (CO2)

parts per million (ppm) **

co2c13

d13C  of CO2

ppm

co2c14

D14C of CO2

ppm

co2o18

d18O of CO2

ppm

cs2

carbon disulfide (CS2)

ppt

dibr

dibromomethane (CH2Br2)

ppt

dicl

dichloromethane (CH2Cl2)

ppt

f112

CFC-112 (CCl3CClF2)

ppt

f113

CFC-113 (CCl2FCClF2)

ppt

f114

CFC-114 and CFC-114a (ClF2CCF2Cl)

ppt

f115

CFC-115 (CClF2CF3)

ppt

f11a

CFC-11 (ion 101; CCl3F)

ppt

f11b

CFC-11 (ion 103; CCl3F)

ppt

f124

HCFC-124 (CHClFCF3)

ppt

f125

HFC-125 (CHF2CF3)

ppt

f13

CFC-13 (CClF3)

ppt

f134

HFC-134 (CHF2CHF2)

ppt

f134a

HFC-134a (CH2FCF3)

ppt

f141b

HCFC-141b (CH3CCl2F)

ppt

f142b

HCFC-142b (CH3CF2Cl)

ppt

f143a

HFC-143a (CH3CF3)

ppt

f152a

HFC-152a (CH3CHF2)

ppt

f160

chloroethane (CH3CH2Cl)

ppt

f227e

HFC-227ea (CF3CHFCF3)

ppt

f23

HFC-23 (CHF3)

ppt

f236fa

HFC-236fa (CF3CH2CF3)

ppt

f32

HFC-32 (CH2F2)

ppt

f365m

HFC-365mfc (CH3CF2CH2CF3)

ppt

fc12

CFC-12 (CCl2F2)

ppt

h1211

bromochlorodifluoromethane (halon 1211; CBrClF2)

ppt

h1301

bromotrifluoromethane (halon 1301; CF3Br)

ppt

h2

hydrogen (H2)

ppb

h2402

dibromotetrafluoroethane (halon 2402; CBrF2CBrF2)

ppt

hf133a

HCFC-133a (CH2ClCF3)

ppt

hf21

HCFC-21 (CHCl2F)

ppt

hf22

HCFC-22 (CHF2Cl)

ppt

ic4h10

i-butane (i-C4H10)

ppt

ic5h12

i-pentane (i-C5H12)

ppt

mcfa

methyl chloroform (ion 97; CH3CCl3)

ppt

mebr

methyl bromide (CH3Br)

ppt

mecl

methyl chloride (CH3Cl)

ppt

n2o

nitrous oxide (N2O)

ppb

nc4h10

n-butane (n-C4H10)

ppt

nc5h12

n-pentane (n-C5H12)

ppt

nc6h14

n-hexane (n-C6H14)

ppt

nf3

nitrogen trifluoride (NF3)

ppt

ocs

carbonyl sulfide (COS)

ppt

p218

perfluoropropane (C3F8)

ppt

pce

tetrachloroethylene (C2Cl4)

ppt

sf6_ccgg

sulfur hexafluoride (SF6)

ppt

sf6_hats

sulfur hexafluoride (SF6)

ppt

so2f2

sulfuryl fluoride (SO2F2)

ppt

tce

trichloroethylene (C2HCl3)

ppt

tol

toluene (C7H8)

ppt

*          Values for geolocation variables do not change (-147.6 E, 65 N)

**        parts per million – ppm – micromol of gas per mol of dry air – 10-6

           parts per billion – ppb – nanomol of gas per mol of dry air – 10-9

           parts per trillion – ppt – picomol of gas per mol of dry air – 10-12

The netcdf files also include a QC flag for each analyte. For example, the benzene ratio QC flag is “benz_ratio_status”. The flag values are the same for all analytes and are provided in Table 3.

Table 3. QC flag value descriptions

QC Flag

Flag Meaning

Description

1

Valid

 

2

Preliminary

Sample measurement is preliminary and has not yet been carefully examined by the PI

3

Deselected

Sample measurement is likely valid but does not meet selection criteria determined by the goals of the CARVE investigation

4

Rejected

Obvious problems during collection or analysis

Calibration:

All measurements are reported as dry air mole fractions on their respective World Meteorological Organization (WMO) standard scales:

  • WMO X2014A CO standard scale (see Novelli et al., 1991)
  • WMO X2007 CO2 standard scale (see Zhao and Tans, 2006)
  • WMO 2004A CH4 standard scale (see Dlugokencky et al., 2005)
  • WMO 2004 CMDL H2 standard scale (Novelli et al., 1999)
  • WMO 2006A N2O standard scale (Hall et al., 2007)
  • WMO 2014 SF6 standard scale (Hall et al., 2007)

Application and Derivation

These data files contain dry mole fractions of CO, CO2, CH4, H2, N2O, and SF6 measured from whole air samples collected at the CARVE tower site between 2012 and 2015. These measurements provide context for aircraft observations obtained during the CARVE project. 

The CARVE project was designed to collect detailed measurements of important greenhouse gases on local to regional scales in the Alaskan arctic and demonstrate new remote sensing and improved modeling capabilities to quantify Arctic carbon fluxes and carbon cycle-climate processes. The CARVE data provide insights into Arctic carbon cycling that may be useful in numerous applications.

Quality Assessment

Table 4. Repeatability of gas detection was determined as 1 standard deviation of ~20 aliquots of natural air measured from a standard cylinder.

Gas

Average Repeatability

CO

UV resonance fluorescence: +/- 0.4 ppb (Gerbig et al., 1999)

CO2

+/- 0.03 ppm (Conway et al., 1994)

CH4

+/- 1.2 ppb (Dlugokencky et al., 1994)

H2

+/- 0.4 ppb (Novelli et al., 1999)

N2O

+/- 0.26 ppb (Dlugokencky et al., 2009)

SF6

+/- 0.03 ppt (Dlugokencky et al., 2009)

Data Acquisition, Materials, and Methods

CARVE research tower

A stationary, tower-based greenhouse gas measurement site, the CARVE tower (NOAA site code CRV), was established in 2011 to give year-round context for the intensive aircraft observations performed throughout the CARVE project. The measurements contained in this data set are from the flask sampling system at the top (32 m.a.g.l.) of CARVE tower in Fox, Alaska (17 km north of Fairbanks; 64.9863 N, 147.5982 W, 611 m.a.s.l.). The tower site was chosen for its high elevation compared to the immediate surrounding mean ground level and its relatively large region of influence to provide temporal and spatial context for CARVE aircraft measurements in interior Alaska.

The surrounding land cover is composed of deciduous and evergreen forest, shrub or scrub, some scattered areas of woody wetlands, mainly south of the Chena River south of Fairbanks, and medium and low intensity developed land in and immediately around Fairbanks (Homer et al., 2015). The tower is located on a ridge, and measurements from the tower represent a wide region of interior Alaska, as indicated by surface influence fields generated from the WRF-STILT modeling framework (Henderson et al., 2015), which show that the tower’s influence region encompasses a substantial part of Alaska (Fig. 1a).

Flask air sampling system

This data set includes measurements from discrete air samples captured by the flask sampling system atop the CARVE tower. 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 Global Monitoring Division’s Global Greenhouse Gas Reference Network (Sweeney et al., 2013).

Figure 2. Flask sampling system 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 sampling plan dictating the interval for filling each flask. 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.

Gas detection

  • Quantities of CO2 in flask air samples were detected using a non-dispersive infrared analyzer and reported in parts per million (micromol CO2 per mol dry air, i.e. ppm). Because detector response is non-linear in the range of atmospheric levels, ambient samples are bracketed during analysis by a set of reference standards used to calibrate detector response.
  • CH4 was isolated from constituent gases through gas chromatography and quantified with flame ionization detection. Measurements are reported in parts per billion (ppb).
  • CO was determined by either resonance fluorescence at ~150 nm with a precision of ±0.4 ppb, or by UV absorption spectroscopy with precision ~1 ppb (Novelli et al., 1998) and reported in ppb.
  • H2 was isolated using gas chromatography, and detected using pulsed-discharge He ionization, providing a precision of ±0.4 ppb for H2 (Novelli et al., 2009). H2 quantities are reported in ppb.
  • The N2O and SF6 sample components were isolated using gas chromatography and quantified with electron capture detection. N2O and SF6 are reported in ppb and parts per trillion (ppt), respectively.

Data Access

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

CARVE: L2 Atmospheric Gas Concentrations, Tower-based Flasks, Alaska, 2012-2015

Contact for Data Center Access Information:

References

Conway, T.J., et al. (1994), Evidence for interannual variability of the carbon cycle from the National Oceanic and Atmospheric Administration/Climate Monitoring and Diagnostics Laboratory Global Air Sampling Network, J. Geophys. Res., 99, 22,831–22,855.

Dlugokencky, E.J., L.P. Steele, P.M. Lang, K.A. Masarie (1994), The growth rate and distribution of atmospheric methane, J. Geophys. Res., 99, 17,021–17,043.

Dlugokencky, E.J., R.C. Myers, P.M. Lang, K.A. Masarie, A.M. Crotwell, K.W. Thoning, B.D. Hall, J.W. Elkins, and L.P. Steele (2005). Conversion of NOAA CMDL atmospheric dry air methane mole fractions to   gravimetrically-prepared standard scale, J. Geophys. Res., 110, D18306 doi: 10.1029/2005JD006035.

Dlugokencky, E. J., et al. (2009), Observational constraints on recent increases in the atmospheric CH4 burden, Geophys. Res. Lett., 36, L18803, doi:10.1029/2009GL039780.

Gerbig, C., S. Schmitgen, D. Kley, A. Volz-Thomas, K. Dewey, D. Haaks (1999), An improved fast-response vacuum-UV resonance fluorescence CO instrument, J. Geophys. Res. 104, 1699 –1704.

Henderson, J.M., J. Eluszkiewicz, M.E. Mountain, T. Nehrkorn, R.Y.-W. Chang, A. Karion, J.B. Miller, C. Sweeney, N. Steiner, S.C. Wofsy, and C.E. Miller (2015). Atmospheric transport simulations in support of the Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE), Atmos. Chem. Phys., 15, 4093-4116, doi:10.5194/acp-15-4093-2015.

Homer, C.G., J.A. Dewitz, L. Yang, S. Jin, P. Danielson, G. Xian, J. Coulston, N.D. Herold, J.D. Wickham, and K. Megown (2015). Completion of the 2011 National Land Cover Database for the conterminous United States-Representing a decade of land cover change information, Photogramm. Eng. Rem. S., 81, 345-354.

Karion, A., C. Sweeney, J.B. Miller, A.E. Andrews, R. Commane, S. Dinardo, J.M. Henderson, J. Lindaas, J.C. Lin, K.A. Luus, T. Newberger, P. Tans, S.C. Wofsy, S. Wolter, and C.E. Miller (2016). Investigating Alaskan methane and carbon dioxide fluxes using measurements from the CARVE tower, Atmos. Chem. Phys., 16, 5383-5398, doi:10.5194/acp-16-5383-2016.

Miller, C.E. and S. J. Dinardo, "CARVE: The Carbon in Arctic Reservoirs Vulnerability Experiment," Aerospace Conference, 2012 IEEE, Big Sky, MT, 2012, pp. 1-17. doi: 10.1109/AERO.2012.6187026

Novelli, P. C., Elkins, J. W., and Steele, L. P. (1991). The development and evaluation of a gravimetric reference scale for measurements of atmospheric carbon monoxide, J. Geophys. Res.-Atmos., 96, 13109–13121, doi:10.1029/91jd01108.

Novelli, P.C., P.M. Lang, K.A. Masarie, D.F. Hurst, R. Myers, J.W. Elkins (1999), Molecular hydrogen in the troposphere: Global distribution and budget, J. Geophys. Res. 104, 30,427-30,444.

Zhao, C., and P.P. Tans (2006). Estimating uncertainty of the WMO Mole Fraction Scale for carbon dioxide in air, J. Geophys.  Res. 111, D08S09, doi: 10.1029/2005JD006003.