References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-11-6425-2011

H2 vertical profiles in the continental boundary layer: measurements at the Cabauw tall tower in The Netherlands

Popa

M. E.

¹ ² Vermeulen

A. T.

¹ van den Bulk

W. C. M.

¹ Jongejan

P. A. C.

¹ Batenburg

A. M.

² Zahorowski

³ Röckmann

Energy research Centre of the Netherlands, Petten, The Netherlands

Institute for Marine and Atmospheric Research Utrecht, Utrecht University, Utrecht, The Netherlands

Australian Nuclear Science and Technology Organisation, Menai, New South Wales, Australia

06 07 2011

11 13 6425 6443

This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.

This article is available from http://www.atmos-chem-phys.net/11/6425/2011/acp-11-6425-2011.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/6425/2011/acp-11-6425-2011.pdf

In-situ, quasi-continuous measurements of atmospheric hydrogen (H2) have been performed since October 2007 at the Cabauw tall tower station in the Netherlands. Mole fractions of H2, CO and several greenhouse gases are determined simultaneously in air sampled successively at four heights, between 20 and 200 m above ground level. 222Rn measurements are performed in air sampled at 20 and 200 m. This H2 dataset represents the first in-situ, quasi-continuous long-term measurement series of vertical profiles of H2 in the lower continental boundary layer. Seasonal cycles are present at all heights in both H2 and CO, and their amplitude varies with the sampling height. The seasonality is evident in both the "baseline" values and in the short term (diurnal to synoptic time scales) variability, the latter being significantly larger during winter. The observed H2 short term signals and vertical gradients are in many cases well correlated to other species, especially to CO. On the other hand, H2 has at times a unique behaviour, due to its particular distribution of sources and sinks. Our estimation for the regional H2 soil uptake flux, using the radon tracer method, is (−1.89 ± 0.26) × 10−5 g/(m2 h), significantly smaller than other recent results from Europe. H2/CO ratios of the traffic emissions computed from our data, with an average of 0.54 ± 0.07 mol:mol, are larger and more variable than estimated in some of the previous studies in Europe. This difference can be explained by a different driving regime, due to the frequent traffic jams in the influence area of Cabauw. The H2/CO ratios of the large scale pollution events have an average of 0.36 ± 0.05 mol:mol; these ratios were observed to slightly increase with sampling height, possibly due to a stronger influence of soil uptake at the lower sampling heights.

References 1

% vor jede Referenz Aalto, T., Lallo, M., Hatakka, J., and Laurila, T.: Atmospheric hydrogen variations and traffic emissions at an urban site in Finland, Atmos. Chem. Phys., 9, 7387–7396, http://dx.doi.org/10.5194/acp-9-7387-2009doi:10.5194/acp-9-7387-2009, 2009.

Bakwin, P. S. and Tans, P. P.: Measurements of carbon dioxide on a very tall tower, Tellus, 47B, 535–549, 1995.

Barnes, D. H., Wofsy, S. C., Fehlau, B. P., Gottlieb, E. W., Elkins, J. W., Dutton, G. S., and Novelli, P. C.: Hydrogen in the atmosphere: Observations above a forest canopy in a polluted environment, J. Geophys. Res.-Atmos., 108, 4197, http://dx.doi.org/10.1029/2001JD001199doi:10.1029/2001JD001199, 2003.

Biraud, S., Ciais, P., Ramonet, M., Simmonds, P., Kazan, V., Monfray, P., O'Doherty, S., Spain, T. G., and Jennings, S. G.: European greenhouse gas emissions estimated from continuous atmospheric measurements and radon 222 at Mace Head, Ireland, J. Geophys. Res., 105, 1351–1366, 2000.

Bonasoni, P., Calzolari, F., Colombo, T., Corazza, E., Santaguida, R., and Tesi, G.: CO and H2 continuous measurements at Mt.Cimone (Italy): Preliminary results, Atmos. Environ., 31, 959–967, http://dx.doi.org/10.1016/S1352-2310(96)00259-2doi:10.1016/S1352-2310(96)00259-2, 1997.

Bond, S. W., Alvarez, R., Vollmer, M. K., Steinbacher, M., Weilenmann, M., and Reimann, S.: Molecular hydrogen (H$_2)$ emissions from gasoline and diesel vehicles, Sci. Total Environ., 408, 3596–3606, http://dx.doi.org/10.1016/j.scitotenv.2010.04.055doi:10.1016/j.scitotenv.2010.04.055, 2010.

Bond, S. W., Vollmer, M. K., Steinbacher, M., Henne, S., and Reimann, S.: Atmospheric molecular hydrogen (H$_2)$: Observations at the high altitude site Jungfraujoch, Switzerland, Tellus B, 64–76, http://dx.doi.org/10.1111/j.1600-0889.2010.00509.xdoi:10.1111/j.1600-0889.2010.00509.x, 2011.

Bousquet, P., Yver, C., Pison, I., Li, Y. S., Fortems, A., Hauglustaine, D., Szopa, S., Rayner, P. J., Novelli, P., Langenfelds, R., Steele, P., Ramonet, M., Schmidt, M., Foster, P., Morfopoulos, C., and Ciais, P.: A three-dimensional synthesis inversion of the molecular hydrogen cycle: Sources and sinks budget and implications for the soil uptake, J. Geophys. Res., 116, D01302, http://dx.doi.org/10.1029/2010JD014599doi:10.1029/2010JD014599, 2011.

Cofer III, W. R., Harriss, R. C., Levine, J. S., and Edahl Jr., R. A.: Vertical distributions of molecular hydrogen off the eastern and Gulf coasts of the United States, J. Geophys. Res., 91, 14561–14567, 1986.

Conrad, R.: Soil Microbial Processes and the Cycling of Atmospheric Trace Gases, Royal Society of London Philosophical Transactions Series A, 351, 219–230, 1995.

Conrad, R.: Soil microorganisms as controllers of atmospheric trace gases (H2, CO, CH4, OCS, N2O, and NO), Microbiology and Molecular Biology Reviews, 60, 609–640, 1996.

Conrad, R. and Seiler, W.: Decomposition of atmospheric hydrogen by soil microorganisms and soil enzymes, Soil Biol. Biochem., 13, 43–49, 1981.

Conrad, R. and Seiler, W.: Influence of Temperature, Moisture, and Organic Carbon on the Flux of H2 and CO Between Soil and Atmosphere: Field Studies in Subtropical Regions, J. Geophys. Res., 90, 5699–5709, 1985.

Constant, P., Poissant, L., and Villemur, R.: Annual hydrogen, carbon monoxide and carbon dioxide concentrations and surface to air exchanges in a rural area (Québec, Canada), Atmos. Environ., 42, 5090–5100, 2008.

Constant, P., Poissant, L., and Villemur, R.: Tropospheric H2 budget and the response of its soil uptake under the changing environment, Sci. Total Environ., 407, 1809–1823, 2009.

Ehhalt, D. H. and Rohrer, F.: The tropospheric cycle of H2: a critical review, Tellus B, 61, 500–535, 2009.

Ehhalt, D. H., Schmidt, U., and Heidt, L. E.: Vertical Profiles of Molecular Hydrogen in the Troposphere and Stratosphere, J. Geophys. Res., 82, 5907–5911, 1977.

Fabian, P., Borchers, R., Weiler, K. H., Schmidt, U., Volz, A., Ehhalt, D. H., Seiler, W., and Müller, F.: Simultaneously Measured Vertical Profiles of H2, CH4, CO, N2O, CFCl3, and CF2Cl2 in the Mid-Latitude Stratosphere and Troposphere, J. Geophys. Res., 84, 3149–3154, http://dx.doi.org/10.1029/JC084iC06p03149doi:10.1029/JC084iC06p03149, 1979.

Glueckauf, E. and Kitt, G. P.: The hydrogen content of atmospheric air at ground level, Q. J. Roy. Meteorol. Soc., 83, 522–528, 1957.

Gödde, M., Meuser, K., and Conrad, R.: Hydrogen consumption and carbon monoxide production in soils with different properties, Biology And Fertility Of Soils, 32, 129–134, 2000.

Grant, A., Stanley, K. F., Henshaw, S. J., Shallcross, D. E., and O'Doherty, S.: High-frequency urban measurements of molecular hydrogen and carbon monoxide in the United Kingdom, Atmos. Chem. Phys., 10, 4715–4724, http://dx.doi.org/10.5194/acp-10-4715-2010doi:10.5194/acp-10-4715-2010, 2010a.

Grant, A., Witham, C. S., Simmonds, P. G., Manning, A. J., and O'Doherty, S.: A 15 year record of high-frequency, in situ measurements of hydrogen at Mace Head, Ireland, Atmos. Chem. Phys., 10, 1203–1214, http://dx.doi.org/10.5194/acp-10-1203-2010doi:10.5194/acp-10-1203-2010, 2010b.

Guo, R. and Conrad, R.: Extraction and characterization of soil hydrogenases oxidizing atmospheric hydrogen, Soil Biol. Biochem., 40, 1149–1154, 2008.

Hammer, S. and Levin, I.: Seasonal variation of the molecular hydrogen uptake by soils inferred from continuous atmospheric observations in Heidelberg, southwest Germany, Tellus B, 61, 556–565, 2009.

Hammer, S., Vogel, F., Kaul, M., and Levin, I.: The H2/CO ratio of emissions from combustion sources: comparison of top-down with bottom-up measurements in southwest Germany, Tellus B, 61, 547–555, 2009.

Harris, S. H., Smith, R. L., and Suflita, J. M.: In situ hydrogen consumption kinetics as an indicator of subsurface microbial activity, FEMS Microbiology Ecology, 60, 220–228, 2007.

Hauglustaine, D. A. and Ehhalt, D. H.: A three-dimensional model of molecular hydrogen in the troposphere, J. Geophys. Res.-Atmos., 107, 4330, http://dx.doi.org/10.1029/2001JD001156doi:10.1029/2001JD001156, 2002.

Henne, S., Brunner, D., Folini, D., Solberg, S., Klausen, J., and Buchmann, B.: Assessment of parameters describing representativeness of air quality in-situ measurement sites, Atmos. Chem. Phys., 10, 3561–3581, http://dx.doi.org/10.5194/acp-10-3561-2010doi:10.5194/acp-10-3561-2010, 2010.

Hurst, D. F., Bakwin, P. S., Myers, R. C., and Elkins, J. W.: Behavior of trace gas mixing ratios on a very tall tower in North Carolina, J. Geophys. Res., 102(D7), 8825–8835, 1997.

Jordan, A. and Steinberg, B.: Calibration of atmospheric hydrogen measurements, Atmos. Meas. Tech., 4, 509–521, http://dx.doi.org/10.5194/amt-4-509-2011doi:10.5194/amt-4-509-2011, 2011.

Khalil, M. A. K. and Rasmussen, R. A.: Global increase of atmospheric molecular hydrogen, Nature, 347, 743–745, 1990.

King, G. M.: Uptake of Carbon Monoxide and Hydrogen at Environmentally Relevant Concentrations by Mycobacteria, Appl. Environ. Microbiol., 69, 7266–7272, http://dx.doi.org/10.1128/aem.69.12.7266-7272.2003doi:10.1128/aem.69.12.7266-7272.2003, 2003a.

King, G. M.: Contributions of Atmospheric CO and Hydrogen Uptake to Microbial Dynamics on Recent Hawaiian Volcanic Deposits, Appl. Environ. Microbiol., 69, 4067–4075, http://dx.doi.org/10.1128/aem.69.7.4067-4075.2003doi:10.1128/aem.69.7.4067-4075.2003, 2003b.

Lallo, M., Aalto, T., Laurila, T., and Hatakka, J.: Seasonal variations in hydrogen deposition to boreal forest soil in southern Finland, Geophys. Res. Lett., 35, L04402, http://dx.doi.org/10.1029/2007GL032357doi:10.1029/2007GL032357, 2008.

Lallo, M., Aalto, T., Hatakka, J., and Laurila, T.: Hydrogen soil deposition at an urban site in Finland, Atmos. Chem. Phys., 9, 8559–8571, http://dx.doi.org/10.5194/acp-9-8559-2009doi:10.5194/acp-9-8559-2009, 2009a.

Lallo, M., Aalto, T., Laurila, T., and Hatakka, J.: Hydrogen soil deposition in northern boreal zone, Boreal Environ. Res, 14, 784–793, 2009b.

Langenfelds, R., Francey, R., Pak, B. C., Steele, L. P., Lloyd, J., Trudinger, C. M., and Allison, C. E.: Interannual growth rate variations of atmospheric CO2 and its $\delta ^13$C, H2, CH4, and CO between 1992 and 1999 linked to biomass burning, Global Biogeochem. Cy., 16, 1048, http://dx.doi.org/10.1029/2001GB001466doi:10.1029/2001GB001466, 2002.

Levin, I.: Atmosphaerisches CO2, Quellen und Senken auf dem Europaeischen Kontinent, PhD, University of Heidelberg, Heidelberg, Germany, 1984.

Levin, I., Glatzel-Mattheier, H., Marik, T., Cuntz, M., Schmidt, M., and Worthy, D. E.: Verification of German methane emission inventories and their recent changes based on atmospheric observations, J. Geophys. Res., 104, 3447–3456, 1999.

Liebl, K. H. and Seiler, W.: CO and H2 destruction at the soil surface, in: Microbial Production and Utilization of Gases, edited by: Schlegel, H. G., Gottschalk, G., and Pfennig, N., Goltze, Göttingen, 215–229, 1976.

Messager, C., Schmidt, M., Ramonet, M., Bousquet, P., Simmonds, P., Manning, A., Kazan, V., Spain, G., Jennings, S. G., and Ciais, P.: Ten years of CO2, CH4, CO and N2O fluxes over Western Europe inferred from atmospheric measurements at Mace Head, Ireland, Atmos. Chem. Phys. Discuss., 8, 1191–1237, http://dx.doi.org/10.5194/acpd-8-1191-2008doi:10.5194/acpd-8-1191-2008, 2008.

Moxley, J. M. and Cape, J. N.: Depletion of carbon monoxide from the nocturnal boundary layer, Atmos. Environ., 31, 1147–1155, 1997.

Neubert, R. E. M., Spijkervet, L. L., Schut, J. K., Been, H. A., and Meijer, H. A. J.: A computer-controlled continuous air drying and flask sampling system, J. Atmos. Ocean. Tech., 21, 651–659, http://dx.doi.org/10.1175/1520-0426(2004)021<0651:ACCADA>2.0.CO;2doi:10.1175/1520-0426(2004)021<0651:ACCADA>2.0.CO;2, 2004.

Novelli, P. C., Lang, P. M., Masarie, K. A., Hurst, D. F., Myers, R., and Elkins, J. W.: Molecular hydrogen in the troposphere: Global distribution and budget, J. Geophys. Res., 104, 30427–30444, 1999.

Pieterse, G., Krol, M. C., Batenburg, A. M., Steele, L. P., Krummel, P. B., Langenfelds, R. L., and Röckmann, T.: Global modelling of H2 mixing ratios and isotopic compositions with the TM5 model, Atmos. Chem. Phys. Discuss., 11, 5811–5866, http://dx.doi.org/10.5194/acpd-11-5811-2011doi:10.5194/acpd-11-5811-2011, 2011.

Pison, I., Bousquet, P., Chevallier, F., Szopa, S., and Hauglustaine, D.: Multi-species inversion of CH4, CO and H2 emissions from surface measurements, Atmos. Chem. Phys., 9, 5281–5297, http://dx.doi.org/10.5194/acp-9-5281-2009doi:10.5194/acp-9-5281-2009, 2009.

Prather, M. J.: An Environmental Experiment with H2?, Science, 302, 581–582, http://dx.doi.org/10.1126/science.1091060doi:10.1126/science.1091060, 2003.

Price, H., Jaeglé, L., Rice, A., Quay, P., Novelli, P. C., and Gammon, R.: Global budget of molecular hydrogen and its deuterium content: Constraints from ground station, cruise, and aircraft observations, J. Geophys. Res.-Atmos., 112, D22108, http://dx.doi.org/10.1029/2006JD008152doi:10.1029/2006JD008152, 2007.

Rhee, T. S., Brenninkmeijer, C. A. M., and Röckmann, T.: The overwhelming role of soils in the global atmospheric hydrogen cycle, Atmos. Chem. Phys., 6, 1611–1625, http://dx.doi.org/10.5194/acp-6-1611-2006doi:10.5194/acp-6-1611-2006, 2006.

Rice, A., Quay, P., Stutsman, J., Gammon, R., Price, H., and Jaegle, L.: Meridional distribution of molecular hydrogen and its deuterium content in the atmosphere, J. Geophys. Res., 115, D12306, http://dx.doi.org/10.1029/2009JD012529doi:10.1029/2009JD012529, 2010.

Sanderson, M. G., Collins, W. J., Derwent, R. G., and Johnson, C. E.: Simulation of Global Hydrogen Levels Using a Lagrangian Three-Dimensional Model, J. Atmos. Chem., 46, 15–28, 2003.

Schmidt, M., Glatzel-Mattheier, H., Sartorius, H., Worthy, D. E., and Levin, I.: Western European N2O emissions - A top-down approach based on atmospheric observations, J. Geophys. Res., 106, 5507–5516, 2001.

Schmidt, M., Graul, R., Sartorius, H., and Levin, I.: The Schauinsland CO2 record: 30 years of continental observations and their implications for the variability of the European CO2 budget, J. Geophys. Res, 108, 4619, http://dx.doi.org/10.1029/2002JD003085doi:10.1029/2002JD003085, 2003.

Schmitt, S., Hanselmann, A., Wollschläger, U., Hammer, S., and Levin, I.: Investigation of parameters controlling the soil sink of atmospheric molecular hydrogen, Tellus B, 61, 416–423, 2009.

Schmidt, U.: Molecular hydrogen in the atmosphere, Tellus, 26, 78–90, 1974.

Schmidt, U.: The latitudinal and vertical distribution of molecular hydrogen in the troposphere, J. Geophys. Res., 83, 941–946, 1978.

Schuler, S. and Conrad, R.: Hydrogen oxidation activities in soil as influenced by pH, temperature, moisture, and season, Biology and Fertility of Soils, 12, 127–130, 1991.

Schultz, M. G., Diehl, T., Brasseur, G. P., and Zittel, W.: Air Pollution and Climate-Forcing Impacts of a Global Hydrogen Economy, Science, 302, 624–627, http://dx.doi.org/10.1126/science.1089527doi:10.1126/science.1089527, 2003.

Scranton, M. I., Barger, W. R., and Herr, F. L.: Molecular hydrogen in the urban troposphere- Measurement of seasonal variability, J. Geophys. Res., 85, 5575–5580, 1980.

Seiler, W., Müller, F., and Oeser, H.: Vertical distribution of chlorofluoromethanes in the upper troposphere and lower stratosphere, Pure and Applied Geophysics, 116, 554–566, 1978.

Simmonds, P. G., Derwent, R. G., O'Doherty, S., Ryall, D. B., Steele, L. P., Langenfelds, R. L., Salameh, P., Wang, H. J., Dimmer, C. H., and Hudson, L. E.: Continuous high-frequency observations of hydrogen at the Mace Head baseline atmospheric monitoring station over the 1994–1998 period, J. Geophys. Res., 105, 12105–12122, 2000.

Smith-Downey, N. V., Randerson, J. T., and Eiler, J. M.: Temperature and moisture dependence of soil H2 uptake measured in the laboratory, Geophys. Res. Lett., 33, L14813, http://dx.doi.org/10.1029/2006GL026749doi:10.1029/2006GL026749, 2006.

Steinbacher, M., Fischer, A., Vollmer, M. K., Buchmann, B., Reimann, S., and Hueglin, C.: Perennial observations of molecular hydrogen (H$_2)$ at a suburban site in Switzerland, Atmos. Environ., 41, 2111–2124, 2007.

Szegvary, T.: European $^222$Rn flux map for atmospheric tracer applications, Ph.D. Thesis, Institute of Environmental Geosciences, University of Basel, Switzerland, Basel, 2007a.

Szegvary, T., Leuenberger, M. C., and Conen, F.: Predicting terrestrial $^222$Rn flux using gamma dose rate as a proxy, Atmos. Chem. Phys., 7, 2789–2795, http://dx.doi.org/10.5194/acp-7-2789-2007doi:10.5194/acp-7-2789-2007, 2007b.

Tromp, T. K., Shia, R. L., Allen, M., Eiler, J. M., and Yung, Y. L.: Potential environmental impact of a hydrogen economy on the stratosphere, Science, 300, 1740–1742, 2003.

Vermeulen, A. T., Eisma, R., Hensen, A., and Slanina, J.: Transport model calculations of NW-European methane emissions, Environ. Sci. Policy, 2, 315–324, 1999.

Vermeulen, A. T., Hensen, A., Popa, M. E., van den Bulk, W. C. M., and Jongejan, P. A. C.: Greenhouse gas observations from Cabauw Tall Tower (1992–2010), Atmos. Meas. Tech., 4, 617–644, http://dx.doi.org/10.5194/amt-4-617-2011doi:10.5194/amt-4-617-2011, 2011.

Vollmer, M. K., Juergens, N., Steinbacher, M., Reimann, S., Weilenmann, M., and Buchmann, B.: Road vehicle emissions of molecular hydrogen (H$_2)$ from a tunnel study, Atmos. Environ., 41, 8355–8369, 2007.

Vollmer, M. K., Walter, S., Bond, S. W., Soltic, P., and Röckmann, T.: Molecular hydrogen (H2) emissions and their isotopic signatures (H/D) from a motor vehicle: implications on atmospheric H2, Atmos. Chem. Phys., 10, 5707–5718, http://dx.doi.org/10.5194/acp-10-5707-2010doi:10.5194/acp-10-5707-2010, 2010.

Warwick, N. J., Bekki, S., Nisbet, E. G., and Pyle, J. A.: Impact of a hydrogen economy on the stratosphere and troposphere studied in a 2-D model, Geophys. Res. Lett., 31, L05107, http://dx.doi.org/10.1029/2003GL019224doi:10.1029/2003GL019224, 2004.

Whittlestone, S. and Zahorowski, W.: Baseline radon detectors for shipboard use: Development and deployment in the First Aerosol Characterization Experiment (ACE 1), J. Geophys. Res., 103, 16743–16751, 1998.

Wilson, S. R., Dick, A. L., Fraser, P. J., and Whittlestone, S.: Nitrous oxide flux estimates for south-eastern Australia, J. Atmos. Chem., 26, 169–188, 1997.

Xiao, X., Prinn, R. G., Simmonds, P. G., Steele, L. P., Novelli, P. C., Huang, J., Langenfelds, R. L., O'Doherty, S., Krummel, P. B., Fraser, P. J., Porter, L. W., Weiss, R. F., Salameh, P., and Wang, R. H. J.: Optimal estimation of the soil uptake rate of molecular hydrogen from the Advanced Global Atmospheric Gases Experiment and other measurements, J. Geophys. Res.-Atmos., 112, D07303, http://dx.doi.org/10.1029/2006JD007241doi:10.1029/2006JD007241, 2007.

Yonemura, S., Kawashima, S., and Tsuruta, H.: Continuous measurements of CO and H2 deposition velocities onto an andisol: uptake control by soil moisture, Tellus B, 51, 688–700, 1999.

Yonemura, S., Yokozawa, M., Kawashima, S., and Tsuruta, H.: Model analysis of the influence of gas diffusivity in soil on CO and H2 uptake, Tellus B, 52, 919–933, 2000.

York, D., Evensen, N. M., Martinez , M. L., and Delgado, J. D. B.: Unified equations for the slope, intercept, and standard errors of the best straight line, American Journal of Physics, 72, 367–375, 2004.

Yver, C., Schmidt, M., Bousquet, P., Zahorowski, W., and Ramonet, M.: Estimation of the molecular hydrogen soil uptake and traffic emissions at a suburban site near Paris through hydrogen, carbon monoxide, and radon-222 semicontinuous measurements, J. Geophys. Res., 114, D18304, http://dx.doi.org/10.1029/2009JD012122doi:10.1029/2009JD012122, 2009.

Yver, C. E., Pison, I. C., Fortems-Cheiney, A., Schmidt, M., Chevallier, F., Ramonet, M., Jordan, A., Søvde, O. A., Engel, A., Fisher, R. E., Lowry, D., Nisbet, E. G., Levin, I., Hammer, S., Necki, J., Bartyzel, J., Reimann, S., Vollmer, M. K., Steinbacher, M., Aalto, T., Maione, M., Arduini, J., O'Doherty, S., Grant, A., Sturges, W. T., Forster, G. L., Lunder, C. R., Privalov, V., Paramonova, N., Werner, A., and Bousquet, P.: A new estimation of the recent tropospheric molecular hydrogen budget using atmospheric observations and variational inversion, Atmos. Chem. Phys., 11, 3375–3392, http://dx.doi.org/10.5194/acp-11-3375-2011doi:10.5194/acp-11-3375-2011, 2011.