News                                                                                                                              Back to Top

  • The 7th WMO-GAW Expert Workshop on Volatile Organic Compounds will be taking place November 4-6, 2019 at the University of Urbino in Urbino Italy. The aim of this workshop is to review the progress in global volatile organic compound (VOC) observations, to discuss new and emerging measurement techniques, and to assess progress in building up quality assurance and global data archiving programs.

  • We are now reporting isoprene and acetylene from the network! After further improvements in the analysis system and thorough testing and intercomparison measurements at the overlapping flask/in-situ sites Summit, Greenland and Hohenpeissenberg we have developed a protocol for quantification of isoprene and acetylene. This development work was presented at the recent WMO-GAW VOC Experts Workshop held in Boulder in May 2017. Two poster presentations detailing this research are available here. Network isoprene and acetylene data starting from 2011 are now available from the NOAA archive.

  • The WMO-GAW VOC Expert Meeting was hosted in Boulder from May 24-26th. The agenda and meeting description are posted here.

Synopsis                                                                                                                        Back to Top

In 2004, NOAA's Global Monitoring Division in collaboration with the Atmospheric Research Laboratory at the Institute of Arctic and Alpine Research at the University of Colorado, Boulder, began a program for measurements of Volatile Organic Compounds (VOC) in air samples collected at remote locations around the globe. This program is one of the core components of the World Meteorological Organization (WMO) Global Atmospheric Watch (GAW) program for Volatile Organic Compounds.  The objectives and approaches of this program have been detailed in these reports:

Schultz M.G., Akimoto H., Bottenheim J., Buchmann B., Galbally I.E., Gilge S., Helmig D., Koide H., Lewis A.C., Novelli P.C., Plass-Dülmer C., Ryerson T.B., Steinbacher M., Steinbrecher R., Tarasova O., Tørseth K., Thouret V., and Zellweger C. (2015) The Global Atmosphere Watch reactive gases measurement network. Elem. Sci. Anth. 3, 1-23, doi: 10.12952/journal.elementa.000067

Establishment of a World Calibration/Instrument Intercomparison for VOC to Serve the WMO Global Atmosphere Watch (GAW) Programme.  WMO-BMBF Workshop on VOC.  World Meteorological Organization Global Atmosphere Watch Report No. 111, 1996.

A WMO/GAW Expert Workshop on Global Long-Term Measurements of Volatile Organic Compounds (VOCs), 2009.  World Meteorological Organization Global Atmosphere Watch Report No. 171.

Helmig, D., Bottenheim J., Galbally I. E., Lewis A., Milton M. J. T., Penkett S., Plass-Duelmer C., Reimann S., Tans P., and Theil S. (2009) Volatile Organic Compounds in the Global Atmosphere. Eos Trans. AGU, 90(52), Feature.


Global Network                                                                                                            Back to Top

Approximately 45 sites have been included since the onset of the program.  A few sites have been added and several others have been discontinued in recent years.  Whole air samples are collected in a pair of glass flasks weekly to bi-weekly at each site and shipped to Boulder for analysis.  Depending on site location and accessibility analyses are typically conducted within 1-9 months after sample collection.
Detailed Sampling Site Information.

Flask Map Currently operated global network sites.

Analytical Procedure                                                                                                   Back to Top

The analytical procedure is based on extraction of ~ 500 ml of air from the flask samples onto a two-stage Peltier-cooled micro-adsorbent trap after drying of the sample air to a dewpoint of -30ºC.  After thermal desorption VOC are separated by gas chromatography on an Alumina PLOT column.  Quantification is done by flame ionization detection.  A series of 3-5 gravimetrically prepared standards is used for calibration of the detector response.   Flask analyses are automated with a series of 12 sample flasks being bracketed by blank and standard runs each.   More details and extensive tests on the analytical procedure were published by Pollmann et al., 2006 and Pollman et al., 2008Our laboratory was audited by the World Calibration Center for Volatile Organic Gases in 2008 and 2011 and found to meet all quality criteria defined by the WMO-GAW program for Reactive Gases on both occasions. 

Collection of whole air samples into a network flask on top of the Pico Mountain, Azores, site.

The analytical system for VOC analysis from the NOAA Cooperative Network Cabon Cycle flasks.  The photograph shows a series of 8 flasks mounted on the flask manifold with the gas chromatograph instrument to the left.

Included Compounds                                                                                                  Back to Top

The selection of gases that are included relies on their chemical stability during sampling, storage, and analyses, and our ability for detection at their observed levels at clean air background locations.  Reported chemical species are the non-methane hydrocarbons (NMHC) ethane, propane, iso-butane, n-butane, acetylene, iso-pentane, n-pentane, hexane, and isoprene. The flask-GC method also provides data for propene, benzene and toluene.  Those gases, however, currently are not reported due to the higher analytical uncertainties in the analysis of these species.

Flask In-Situ Comparisons                                                                                         Back to Top

At two sites, i.e. the German Weather Service Hohenpeissenberg Observatory and at Summit, Greenland, parallel VOC measurements are being conducted with flask sample collection and by in-situ monitoring at the site with a GC system.  These observations allow evaluation and quality control of the of bi-weekly flask sample collection with the much higher resolution in-situ measurements.  These measurements are continuing and further analyses and evaluations are ongoing.  

Eight month comparison of propane quantification results from flasks and in-situ measurements at Hohenpeissenberg Observatory (DWD).


Eight month comparison of isoprene quantification results from flaks and in-situ measurements at Hohenpeissenberg Observatory (DWD).


Two year comparison of ethane quantification results from in-situ measurements and NOAA/INSTAAR bi-weekly flask samples from Summit, Greenland.


Results of Spacial and Seasonal Distribution                                                          Back to Top

3D Presentations of ethane, propane, butane, and pentane global distribution.

Global distribution of ethane (C2H6) from 2005- April 2016.


Global distribution of propane (C3H8) from 2005- March 2015.


Global distribution of iso-butane (i-C4H10) from 2005- March 2015.


Global distribution of n-butane (n-C4H10) from 2005- March 2015.


Global distribution of i-pentane (i-C5H12) from 2005- March 2015.


Global distribution of n-pentane (n-C5H12) from 2005- March 2015.

Data Products and Policy                                                                                            Back to Top

After completion of all calibration and quality control steps, final data are reported to the NOAA GMD data portal and from there they are released to the World Data Centre of Greenhouse Gases in Tokyo approximately 18-24 months after sample collection. Data are in the process of being submitted to the World Data Center for Reactive Gases, hosted by EBAS in Norway. Progress on the submission can be viewed here. Data from this program are for public use in scientific research.  We request that the Program Principal Investigator (D. Helmig) be contacted to discuss intentions to utilize these data in scientific publication for possible consideration of co-authorship.

Publications Resulting From This Program                                                              Back to Top

Thompson R. L., Nisbet E. G., Pisso I., Stohl A., Blake D., Dlugokencky E. J., Helmig D., and White J. W. C. (2018) Variability in atmospheric methane from fossil fuel and microbial sources over the last three decades. Geophys. Res. Lett. 45, 11,499–11,508.

Monks S. A., Wilson C., Emmons L. K., Hannigan J., Helmig D., Blake N. J., and Blake D. R. Using an inverse model to reconcile differences in simulated and observed global ethane concentrations and trends between 2008 and 2014, J. Geophys. Res., doi:10.1029/2017JD028112. (link to article)

Rossabi S., and Helmig D. (2018) Changes in atmospheric butanes and pentanes and their isomeric ratios in the Continental United States, J. Geophys. Res. Atmos. 123, 3772-3790, doi:10.1002/2017JD027709. (link to article)

Tzompa-Sosa Z.A., Mahieu E., Franco B., Keller C.A., Turner A.J., Helmig D., Fried A., Richter D., Weibring P., Walega J., Yacovitch T.I., Herndon S.C., Blake D.R., Hase F., Hannigan J.W., Conway S., Strong K., Schneider M., and Fischer E.V. (2017) Revisiting global fossil fuel and biofuel emissions of ethane, J. Geophys. Res. 122, 2493–2512, doi:10.1002/ 2016JD025767. (link to article)

Feldman D. R., Collins W. D., Biraud S. C., Risser M. D., Turner D. D., Gero P. J., Tadić J., Helmig D., Xie S., Mlawer E. J., Shippert T. R., and Torn M. S. (2018) Observationally derived rise in methane surface forcing mediated by water vapour trends, Nature Geoscience, 11, 238-243, doi:10.1038/s41561-018-0085-9. (link to article)

Oil and gas emissions could far exceed current estimates, in Editorial, Nature. (2018)

Dalsøren S.B., Myhre G., Hodnebrog Ø., Myhre C.L., Stohl A., Pisso I., Schwietzke S., Höglund-Isaksson L., Helmig D., Reimann S., Sauvage S., Schmidbauer N., Read K.A., Carpenter L.J., Lewis A.C., Punjabi S., and Wallasch M. (2018) Discrepancy between simulated and observed ethane and propane levels explained by underestimated fossil emissions. Nature Geosci. 11, 178–184.

WMO (2017) WMO Reactive Gases Bulletin: Highlights from the Global Atmosphere Watch Programme, World Meteorological Organization. (link to bulletin)

Huang Y., Wu S., Kramer L. J., Helmig D., and Honrath R. E. (2017) Surface ozone and its precursors at Summit, Greenland: comparison between observations and model simulations, Atmos. Chem. Phys., 17(23), 14661-14674, doi:10.5194/acp-17-14661-2017.(link to article)

Schultz M.G., Akimoto H., Bottenheim J., Buchmann B., Galbally I.E., Gilge S., Helmig D., Koide H., Lewis A.C., Novelli P.C., Plass-Dülmer C., Ryerson T.B., Steinbacher M., Steinbrecher R., Tarasova O., Tørseth K., Thouret V., and Zellweger C. (2015) The Global Atmosphere Watch reactive gases measurement network. Elem. Sci. Anth. 3: 000067. doi: 10.12952/journal.elementa.000067. (link to article)

Newland M.J., Martinerie P., Witrant E., Helmig D., Worton D.R., Hogan C., Sturges W.T., and Reeves C.E. (2017) Changes to the chemical state of the Northern Hemisphere atmosphere during the second half of the twentieth century, Atmos. Chem. Phys., 17, 8269-8283. (link to article)

Pollmann J., Helmig D., Liptzin D., Thompson C.R., Hueber J., Tans P.P., and Lelieveld J. (2016) Variability analyses, site characterization, and regional [OH] estimates using trace gas measurements from the NOAA Global Greenhouse Gas Reference Network. Elementa 4: 000128. doi: 10.12952/journal.elementa.000128. (link to article)

Helmig D., Rossabi S., Hueber J., Tans P., Montzka S.A., Masarie K., Thoning K., Plass-Duelmer C., Claude A., Carpenter L.J., Lewis A.C., Punjabi S., Reimann S., Vollmer M.K., Steinbrecher R., Hannigan J.W., Emmons L.K., Mahieu E., Franco B., Smale D., and Pozzer A. (2016) Reversal of global atmospheric ethane and propane trends largely due to US oil and natural gas production, Nature Geosci, 9, 490-495. (link to article)

Lawson S.J., Selleck P.W., Galbally I.E., Keywood M.D., Harvey M.J., Lerot C., Helmig D., Ristovski Z. (2015) Seasonal in situ observations of glyoxal and methylglyoxal over the temperate oceans of the Southern Hemisphere. Atmos. Chem. Phys. 15, 223-240. (link to article)

Emmons L.K., Arnold S.R., Monks S.A., Huijnen V., Tilmes S., Law K.S., Thomas J.L., Raut J.C., Bouarar I., Turquety S., Long Y., Duncan B., Steenrod S., Strode S., Flemming J., Mao J., Langner J., Thompson A.M., Tarasick D., Apel E.C., Blake D.R., Cohen R.C., Dibb J., Diskin G.S., Fried A., Hall S.R., Huey L.G., Weinheimer A.J., Wisthaler A., Mikoviny T., Nowak J., Peischl J., Roberts J.M., Ryerson T., Warneke C., and Helmig D. (2015) The POLARCAT Model Intercomparison Project (POLMIP): overview and evaluation with observations, Atmos. Chem. Phys., 15(12), 6721-6744. (link to article)

Helmig D., Petrenko V., Martinerie P., Witrant E., Röckmann T., Zuiderweg A., Holzinger R., Hueber J., Thompson C., White J.W.C., Sturges W., Baker A., Blunier T., Etheridge D., Rubino M., and Tans P. (2014) Reconstruction of Northern Hemisphere 1950 – 2010 atmospheric non-methane hydrocarbons. Atmos. Chem. Phys. 14, 1463-1483, doi:10.5194/acpd-14-1463-2014. (link to article)

Simpson I.J., Sulbaek Andersen M.P., Meinardi S., Bruhwiler L., Blake N.J., Helmig D., Rowland F.S., and Blake D.R. (2012) Long-term decline of global atmospheric ethane concentrations and implications for methane, Nature, 488(7412), 490-494. (link to article)

Pozzer A., Pollmann J., Taraborrelli D., Jöckel P., Helmig D., Tans P., Hueber J., and Lelieveld J. (2010) Observed and simulated global distribution and budget of atmospheric C2-C5 alkanes, Atmos. Chem. Phys., 10(9), 4403-4422. (link to article)

Helmig D., Bottenheim J., Galbally I.E., Lewis A., Milton M.J.T., Penkett S., Plass-Duelmer C., Reimann S., Tans P., and Thiel S. (2009) Volatile Organic Compounds in the Global Atmosphere, Eos, Transactions American Geophysical Union, 90(52), 513-514. (link to article)

Pollmann J., Helmig D., Hueber J., Plass-Duelmer C., and Tans P. (2008) Sampling, storage, and analysis of C2-C7 non-methane hydrocarbons from the US National Oceanic and Atmospheric Administration Cooperative Air Sampling Network glass flasks. J. Chromatogr., 1188, 75-87. (link to article)

Pollmann J., Helmig D., Hueber J., Tanner D., and Tans P. (2006) Evaluation of adsorbent materials for cryogen-free trapping-one stage-GC analysis of atmospheric C2-C6 non-methane hydrocarbons. J. Chrom., 1134, 1-15. (link to article)

Recognition                                                                                                                 Back to Top

WMO-GAW VOC Expert Meeting, May 2017

Global Atmosphere Watch

World Calibration Centre for Volatile Organic Compounds (WCC-VOC)

NOAA ESRL Global Monitoring Division

World Data Centre for Greenhouse Gases

Institute of Arctic and Alpine Research

D. Helmig1
J. Hueber1
P. Tans2

1) Institute for Arctic and Alpine Research, University of Colorado Boulder, Boulder, Colorado, USA

2) NOAA Earth System Research Laboratory, Boulder, Colorado, USA


Contact Information                                                                                                    Back to Top

Detlev Helmig
Institute of Arctic and Alpine Research
University of Colorado
Boulder, CO 80303, USA
001 303 492-2509

Last Updated: September, 2019 - Webmaster: Jashan Chopra View Page Stats