References

ACP

Atmospheric Chemistry and Physics

ACP

1680-7324

Copernicus GmbH

Göttingen, Germany

10.5194/acp-11-6749-2011

Isoprene oxidation mechanisms: measurements and modelling of OH and HO2 over a South-East Asian tropical rainforest during the OP3 field campaign

Stone

¹ ² Evans

M. J.

¹ Edwards

P. M.

² Commane

² ⁹ Ingham

² ³ Rickard

A. R.

² ³ Brookes

D. M.

⁴ Hopkins

⁵ ⁶ Leigh

R. J.

⁴ Lewis

A. C.

⁵ ⁶ Monks

P. S.

⁴ Oram

⁷ ⁸ Reeves

C. E.

⁷ ⁸ Stewart

⁷ ¹⁰ Heard

D. E.

² ³

School of Earth & Environment, University of Leeds, Leeds, UK

School of Chemistry, University of Leeds, Leeds, UK

National Centre for Atmospheric Science, University of Leeds, Leeds, UK

Department of Chemistry, University of Leicester, Leicester, UK

Department of Chemistry, University of York, York, UK

National Centre for Atmospheric Science, University of York, York, UK

School of Environmental Sciences, University of East Anglia, Norwich, UK

National Centre for Atmospheric Science, University of East Anglia, Norwich, UK

now at: School of Engineering & Applied Sciences, Harvard University, Cambridge, USA

now at: Department of Chemistry, University of Reading, Reading, UK

14 07 2011

11 13 6749 6771

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/11/6749/2011/acp-11-6749-2011.html

The full text article is available as a PDF file from http://www.atmos-chem-phys.net/11/6749/2011/acp-11-6749-2011.pdf

Forests are the dominant source of volatile organic compounds into the atmosphere, with isoprene being the most significant species. The oxidation chemistry of these compounds is a significant driver of local, regional and global atmospheric composition. Observations made over Borneo during the OP3 project in 2008, together with an observationally constrained box model are used to assess our understanding of this oxidation chemistry. In line with previous work in tropical forests, we find that the standard model based on MCM chemistry significantly underestimates the observed OH concentrations. Geometric mean observed to modelled ratios of OH and HO2 in airmasses impacted with isoprene are 5.32−4.43+3.68 and 1.18−0.30+0.30 respectively, with 68 % of the observations being within the specified variation. We implement a variety of mechanistic changes into the model, including epoxide formation and unimolecular decomposition of isoprene peroxy radicals, and assess their impact on the model success. We conclude that none of the current suggestions can simultaneously remove the bias from both OH and HO2 simulations and believe that detailed laboratory studies are now needed to resolve this issue.

References 1

Alicke, B., Hebestreit, K., Stutz, J., and Platt, U.: Iodine oxide in the marine boundary layer, Nature, 397, 572–573, 1999.

Anglada, J. M. and Domingo, V. M.: Mechanism for the Gas-Phase Reaction between Formaldehyde and Hydroperoxyl Radical. A Theoretical Study, J. Phys. Chem. A., 109, 10786–10794, 2005.

Archibald, A. T., Cooke, M. C., Utembe, S. R., Shallcross, D. E., Derwent, R. G., and Jenkin, M. E.: Impacts of mechanistic changes on HOx formation and recycling in the oxidation of isoprene, Atmos. Chem. Phys., 10, 8097–8118, http://dx.doi.org/10.5194/acp-10-8097-2010doi:10.5194/acp-10-8097-2010, 2010.

Archibald, A. T., Levine, J. G., Abraham, N. L., Cooke, M. C., Edwards, P. E., Heard, D. E., Jenkin, M. E., Pike, R. C., Monks, P., Shallcross, D. E., Teford, P. J., Whalley, L. K., and Pyle, J. A.: Impacts of HOx regeneration and recycling in the oxidation of isoprene: Consequences for the composition of past, present and future atmospheres, Geophys. Res. Lett., 38, L05804, http://dx.doi.org/10.1029/2010GL046520doi:10.1029/2010GL046520, 2011.

Bloss, W. J., Gravestock, T. J., Heard, D. E., Ingham, T., Johnson, G. P., and Lee, J. D.: Application of a compact all solid-state laser system to the in situ detection of atmospheric OH, HO2, NO and IO by laser-induced fluorescence, J. Environ. Monit., 5, 21–28, 2003.

Brough, N., Reeves, C. E., Penkett, S. A., Stewart, D. J., Dewey, K., Kent, J., Barjat, H., Monks, P. S., Ziereis, H., Stock, P., Huntrieser, H., and Schlager, H.: Intercomparison of aircraft instruments on board the C-130 and Falcon~20 over southern Germany during EXPORT~2000, Atmos. Chem. Phys., 3, 2127–2138, http://dx.doi.org/10.5194/acp-3-2127-2003doi:10.5194/acp-3-2127-2003, 2003.

Burrows, J. P., Moortgat, G. K., Tyndall, G. S., Cox, R. A., Jenkin, M. E., Hayman, G. D., and Veyret, B.: Kinetics and Mechanism of the Photooxidation of Formaldehyde. 2. Molecular Modulation Studies, J. Phys. Chem., 93, 2375–2382, 1989.

Butler, T. M., Taraborrelli, D., Brühl, C., Fischer, H., Harder, H., Martinez, M., Williams, J., Lawrence, M. G., and Lelieveld, J.: Improved simulation of isoprene oxidation chemistry with the ECHAM5/MESSy chemistry-climate model: lessons from the GABRIEL airborne field campaign, Atmos. Chem. Phys., 8, 4529–4546, http://dx.doi.org/10.5194/acp-8-4529-2008doi:10.5194/acp-8-4529-2008, 2008.

Capes, G., Murphy, J. G., Reeves, C. E., McQuaid, J. B., Hamilton, J. F., Hopkins, J. R., Crosier, J., Williams, P. I., and Coe, H.: Secondary organic aerosol from biogenic VOCs over West Africa during AMMA, Atmos. Chem. Phys., 9, 3841–3850, http://dx.doi.org/10.5194/acp-9-3841-2009doi:10.5194/acp-9-3841-2009, 2009.

Carslaw, N., Creasey, D. J., Harrison, D., Heard, D. E., Hunter, M. C., Jacobs, P. J., Jenkin, M. E., Lee, J. D., Lewis, A. C., Pilling, M. J., Saunders, S. M., and Seakins, P. W.: OH and HO2 radical chemistry in a forested region of north-western Greece, Atmos. Environ., 35, 4725–4737, 2001.

Chen, D., Jin, H., Wang, Z., Zhang, L., and Qi, F.: Unimolecular Decomposition of Ethyl Hydroperoxide: Ab Initio/Rice-Ramsperger-Kassel-Marcus Theoretical Prediction of Rate Constants, J. Phys. Chem. A., 115(5), 602–611, 2011.

Commane, R., Floquet, C. F. A., Ingham, T., Stone, D., Evans, M. J., and Heard, D. E.: Observations of OH and HO2 radicals over West Africa, Atmos. Chem. Phys., 10, 8783–8801, http://dx.doi.org/10.5194/acp-10-8783-2010doi:10.5194/acp-10-8783-2010, 2010.

da Silva, G.: Hydroxyl radical regeneration in the photochemical oxidation of glyoxal: kinetics and mechanism of the HC(O)CO + O2 reaction, Phys. Chem. Chem. Phys., 12, 6698–6705, 2010a.

da Silva, G.: Oxidation of Carboxylic Acids Regenerates Hydroxyl Radicals in the Unpolluted and Nighttime Troposphere, J. Phys. Chem. A., 114, 6861–6869, 2010b.

da Silva, G.: Kinetics and Mechanism of the Glyoxal + HO2 Reaction: Conversion of HO2 to OH by Carbonyls, J. Phys. Chem. A., 115, 291–297, 2011.

da Silva, G., Graham, C., and Wang, Z. F.: Unimolecular β-Hydroperoxy Radical Decomposition with OH Recycling in the Photochemical Oxidation of Isoprene, Environ. Sci. Technol., 44, 250–256, 2010.

Dillon, T. J. and Crowley, J. N.: Direct detection of OH formation in the reactions of HO2 with CH3C(O)O2 and other substituted peroxy radicals, Atmos. Chem. Phys., 8, 4877–4889, http://dx.doi.org/10.5194/acp-8-4877-2008doi:10.5194/acp-8-4877-2008, 2008.

Edwards, G. D. and Monks, P. S.: Performance of a single-monochromator diode array spectroradiometer for the determination of actinic flux and atmospheric photolysis frequencies, J. Geophys. Res., 108(D16), 8546, http://dx.doi.org/10.1029/2002JD002844doi:10.1029/2002JD002844, 2003.

Edwards, P. M., Whalley, L. K., Furneaux, K. L., Stone, D., Goddard, A., Ingham, T., Hopkins, J., Jones, C., Lee, J. D.,Lewis, A. C., Moller, S., Robinson, N., Evans, M. J., and Heard, D. E.: OH reactivity in a South East Asian Tropical rainforest, Atmos. Chem. Phys. Discuss., in preparation, 2011.

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

Emmerson, K. M. and Evans, M. J.: Comparison of tropospheric gas-phase chemistry schemes for use within global models, Atmos. Chem. Phys., 9, 1831–1845, http://dx.doi.org/10.5194/acp-9-1831-2009doi:10.5194/acp-9-1831-2009, 2009.

Fuchs, H., Bohn, B., Hofzumahaus, A., Holland, F., Lu, K. D., Nehr, S., Rohrer, F., and Wahner, A.: Detection of HO2 by laser-induced fluorescence: calibration and interferences from RO2 radicals, Atmos. Meas. Tech., 4, 1209–1225, http://dx.doi.org/10.5194/amt-4-1209-2011doi:10.5194/amt-4-1209-2011, 2011.

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

GLOBALVIEW-CH4, 2009: Cooperative Atmospheric Data Integration Project – Methane. CD-ROM, NOAA ESRL, Boulder, Colorado, also available on Internet via anonymous FTP to ftp://ftp.cmdl.noaa.gov, path: ccg/CH4/GLOBALVIEW, 2009, access: 26 January 2011.

Hard, T. M., O'Brien, R. J., Chan, C. Y., and Mehrabzadeh, A. A.: Tropospheric Free-Radical Determination by FAGE, Environ. Sci. Technol., 18, 768–777, 1984.

Hasson, A. S., Tyndall, G. S., and Orlando, J. J.: A product yield study of the reaction of HO2 radicals with ethyl peroxy (C2H$_5$O2), acetyl peroxy (CH3C(O)O2), and acetonyl peroxy (CH3C(O)CH2O2) radicals, J. Phys. Chem. A, 108, 5979–5989, 2004.

Heard, D. E. and Pilling, M. J.: Measurement of OH and HO2 in the troposphere, Chem. Reviews, 103, 5163–5198, 2003.

Hewitt, C. N., Lee, J. D., MacKenzie, A. R., Barkley, M. P., Carslaw, N., Carver, G. D., Chappell, N. A., Coe, H., Collier, C., Commane, R., Davies, F., Davison, B., DiCarlo, P., Di Marco, C. F., Dorsey, J. R., Edwards, P. M., Evans, M. J., Fowler, D., Furneaux, K. L., Gallagher, M., Guenther, A., Heard, D. E., Helfter, C., Hopkins, J., Ingham, T., Irwin, M., Jones, C., Karunaharan, A., Langford, B., Lewis, A. C., Lim, S. F., MacDonald, S. M., Mahajan, A. S., Malpass, S., McFiggans, G., Mills, G., Misztal, P., Moller, S., Monks, P. S., Nemitz, E., Nicolas-Perea, V., Oetjen, H., Oram, D. E., Palmer, P. I., Phillips, G. J., Pike, R., Plane, J. M. C., Pugh, T., Pyle, J. A., Reeves, C. E., Robinson, N. H., Stewart, D., Stone, D., Whalley, L. K., and Yin, X.: Overview: oxidant and particle photochemical processes above a south-east Asian tropical rainforest (the OP3 project): introduction, rationale, location characteristics and tools, Atmos. Chem. Phys., 10, 169–199, http://dx.doi.org/10.5194/acp-10-169-2010doi:10.5194/acp-10-169-2010, 2010.

Hofzumahaus, A., Rohrer, F., Lu, K., Bohn, B., Brauers, T., Chang, C. C., Fuchs, H., Holland, F., Kita, K., Kondo, Y., Li, X., Lou, S., Shao, M., Zeng, L., Wahner, A., and Zhang, Y.: Amplified trace gas removal in the troposphere, Science, 324, 1702–1704, 2009.

Hopkins, J. R., Lewis, A. C., and Read, K. A.: A two-column method for long-term monitoring of non-methane hydrocarbons (NMHCs) and oxygenated volatile organic compounds (oVOCs), J. Environ. Monit., 5, 8–13, 2003.

Hopkins, J. R., Evans, M. J., Lee, J. D., Lewis, A. C., H Marsham, J., McQuaid, J. B., Parker, D. J., Stewart, D. J., Reeves, C. E., and Purvis, R. M.: Direct estimates of emissions from the megacity of Lagos, Atmos. Chem. Phys., 9, 8471–8477, http://dx.doi.org/10.5194/acp-9-8471-2009doi:10.5194/acp-9-8471-2009, 2009.

Jaegle, L., Jacob, D. J., Brune, W. H., Faloona, I., Tan, D., Heikes, B. G., Kondo, Y., Sachse, G. W., Anderson, B., Gregory, G. L., Singh, H. B., Pueschel, R., Ferry, G., Blake, D. R., and Shetter, R. E.: Photochemistry of HOx in the uppoer troposphere at northern midlatitudes, J. Geophys. Res., 105(D3), 3877–3892, 2000.

Jenkin, M. E., Saunders, S. M., Wagner, V., and Pilling, M. J.: Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part B): tropospheric degradation of aromatic volatile organic compounds, Atmos. Chem. Phys., 3, 181–193, http://dx.doi.org/10.5194/acp-3-181-2003doi:10.5194/acp-3-181-2003, 2003.

Jenkin, M. E., Hurley, M. D., and Wallington, T. J.: Investigation of the radical product channel of the CH3C(O)O2+HO2 reaction in the gas phase, Phys. Chem. Chem. Phys., 9, 3149–3162, 2007.

Jenkin, M. E., Hurley, M. D., and Wallington, T. J.: Investigation of the radical product channel of the CH3C(O)CH2O2+HO2 reaction in the gas phase, Phys. Chem. Chem. Phys., 10, 4274–4280, 2008.

Jenkin, M. E., Hurley, M. D., and Wallington, T. J.: Investigation of the Radical Product Channel of the CH3OCH2O2 + HO2 Reaction in the Gas Phase, J. Phys. Chem. A., 114, 408–416, 2010.

Jones, C. E., Hopkins, J. R., and Lewis, A. C.: In situ measurements of isoprene and monoterpenes within a South-East Asian tropical rainforest, Atmos. Chem. Phys. Discuss., 11, 1189–1218, http://dx.doi.org/10.5194/acpd-11-1189-2011doi:10.5194/acpd-11-1189-2011, 2011.

Kolmorogov, A.: Sulla determinazione empirica di una legge di distribuzione, G. Inst. Ital. Attuari, 4, 83, 1933.

Kruskal, W. H. and Wallis, W. A.: Use of ranks in one-criterion variance analysis, J. Am. Stat. Assoc., 47(260), 583–621, 1952.

Kubistin, D., Harder, H., Martinez, M., Rudolf, M., Sander, R., Bozem, H., Eerdekens, G., Fischer, H., Gurk, C., Kl�pfel, T., K�nigstedt, R., Parchatka, U., Schiller, C. L., Stickler, A., Taraborrelli, D., Williams, J., and Lelieveld, J.: Hydroxyl radicals in the tropical troposphere over the Suriname rainforest: comparison of measurements with the box model MECCA, Atmos. Chem. Phys., 10, 9705–9728, http://dx.doi.org/10.5194/acp-10-9705-2010doi:10.5194/acp-10-9705-2010, 2010.

Le Crane, J. P., Rayez, M. T., Rayez, J. C., and Villenave, E.: A reinvestigation of the kinetics and the mechanism of the CH3C(O)O2+HO2 reaction using both experimental and theoretical approaches, Phys. Chem. Chem. Phys., 8, 2163–2171, 2006.

Lelieveld, J., Butler, T. M., Crowley, J. N., Dillon, T. J., Fischer, H., Ganzeveld, L., Harder, H., Lawrence, M. G., Martinez, M., Taraborrelli, D., and Williams, J.: Atmospheric oxidation capacity sustained by a tropical forest, Nature, 452, 737–740, 2008.

Mahajan, A. S., Oetjen, H., Saiz-Lopez, A., Lee, J. D., McFiggans, G. B., and Plane, J. M. C.: Reactive iodine species in a semi-polluted environment, Geophys. Res. Lett., 36, L16803, http://dx.doi.org/10.1029/2009GL038018doi:10.1029/2009GL038018, 2009.

Mao, J., Ren, X., Brune, W. H., Olson, J. R., Crawford, J. H., Fried, A., Huey, L. G., Cohen, R. C., Heikes, B., Singh, H. B., Blake, D. R., Sachse, G. W., Diskin, G. S., Hall, S. R., and Shetter, R. E.: Airborne measurement of OH reactivity during INTEX-B, Atmos. Chem. Phys., 9, 163–173, http://dx.doi.org/10.5194/acp-9-163-2009doi:10.5194/acp-9-163-2009, 2009.

Martinez, M., Harder, H., Kubistin, D., Rudolf, M., Bozem, H., Eerdekens, G., Fischer, H., Klüpfel, T., Gurk, C., Königstedt, R., Parchatka, U., Schiller, C. L., Stickler, A., Williams, J., and Lelieveld, J.: Hydroxyl radicals in the tropical troposphere over the Suriname rainforest: airborne measurements, Atmos. Chem. Phys., 10, 3759–3773, http://dx.doi.org/10.5194/acp-10-3759-2010doi:10.5194/acp-10-3759-2010, 2010.

Monks, P. S.: Gas-phase radical chemistry in the troposphere, Chem. Soc. Rev., 34(5), 376–395, 2005.

Murphy, J. G., Oram, D. E., and Reeves, C. E.: Measurements of volatile organic compounds over West Africa, Atmos. Chem. Phys., 10, 5281–5294, http://dx.doi.org/10.5194/acp-10-5281-2010doi:10.5194/acp-10-5281-2010, 2010.

Nguyen, T. L., Vereecken, L., and Peeters, J.: HOx Regeneration in the Oxidation of Isoprene III: Theoretical Study of the key Isomerisation of the \textitZ-δ-hydroxy-peroxy Isoprene Radicals, Chem. Phys. Chem., 11, 3996–4001, 2010

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(D23), 30427–30444, 1999.

Olson, J. R., Crawford, J. H., Chen, G., Fried, A., Evans, M. J., Jordan, C. E., Sandholm, S. T., Davis, D. D., Anderson, B. E., Avery, M. A., Barrick, J. D., Blake, D. R., Brune, W. H., Eisele, F. L., Flocke, F., Harder, H., Jacob, D. J., Kondo, Y., Lefer, B. L., Martinez, M., Mauldin, R. L., Sachse, G. W., Shetter, R. E., Singh, H. N., Talbot, R. W., and Tan, D.: Testing fast photochemical theory during TRACE-P based on measurements of OH, HO2 and CH2O, J. Geophys. Res., 109, D15S10, http://dx.doi.org/10.1029/2003JD004278doi:10.1029/2003JD004278, 2004.

Olson, J. R., Crawford, J. H., Chen, G., Brune, W. H., Faloona, I. C., Tan, D., Harder, H., and Martinez, M.: A reevaluation of airborne HO$_\mathbf x$ observations from NASA field campaigns, J. Geophys. Res., 111, D10301, http://dx.doi.org/10.1029/2005JD006617doi:10.1029/2005JD006617, 2006.

Paulot, F., Crounse, J. D., Kjaergaard, H. G., Kurten, A., St. Clair, J. M., Seinfeld, J. H., and Wennberg, P. O.: Unexpected Epoxide Formation in the Gas-Phase Photooxidation of Isoprene, Science, 325, 730–733, 2009.

Peeters, J. and Muller, J.-F.: HOx radical regeneration in isoprene oxidation via peroxy radical isomerisations. II: experimental evidence and global impact, Phys. Chem. Chem. Phys., 12, 14227–14235, 2010.

Peeters, J., Nguyen, T. L., and Vereecken, L.: HOx radical regeneration in the oxidation of isoprene, Phys. Chem. Chem. Phys., 11(28), 5935–5939, 2009.

Pugh, T. A. M., MacKenzie, A. R., Hewitt, C. N., Langford, B., Edwards, P. M., Furneaux, K. L., Heard, D. E., Hopkins, J. R., Jones, C. E., Karunaharan, A., Lee, J., Mills, G., Misztal, P., Moller, S., Monks, P. S., and Whalley, L. K.: Simulating atmospheric composition over a South-East Asian tropical rainforest: performance of a chemistry box model, Atmos. Chem. Phys., 10, 279–298, http://dx.doi.org/10.5194/acp-10-279-2010doi:10.5194/acp-10-279-2010, 2010.

Ren, X., Harder, H., Martinez, M., Faloona, I. C., Tan, D., Lesher, R. L., Di Carlo, P., Simpas, J. B., and Brune, W. H.: Interference Testing for Atmospheric HOx Measurements by Laser-induced Fluorescence, J. Atmos. Chem., 47, 169–190, 2004.

Ren, R., Olson, J. R., Crawford, J. H., Brune, W. H., Mao, J., Long, R. B., Chen, Z., Chen, G., Avery, M. A., Sachse, G. W., Barrick, J. D., Diskin, G. S., Huey, L. G., Fried, A., Cohen, R. C., Heikes, B., Wennberg, P. O., Singh, H. B., Blake, D. R., and Shetter, R. E.: HOx chemistry during INTEX-A 2004: Observation, model calculation, and comparison with previous studies, J. Geophys. Res., 113, D05310, http://dx.doi.org/10.1029/2007JD009166doi:10.1029/2007JD009166, 2008.

Saunders, S. M., Jenkin, M. E., Derwent, R. G., and Pilling, M. J.: Protocol for the development of the Master Chemical Mechanism, MCM v3 (Part A): tropospheric degradation of non-aromatic volatile organic compounds, Atmos. Chem. Phys., 3, 161–180, http://dx.doi.org/10.5194/acp-3-161-2003doi:10.5194/acp-3-161-2003, 2003.

Smirnov, N. V.: Tables for estimating the goodness of fit of empirical distributions, Ann. Math. Stat., 19, 279, 1948.

Stavrakou, T., Peeters, J., and Müller, J.-F.: Improved global modelling of HOx recycling in isoprene oxidation: evaluation against the GABRIEL and INTEX-A aircraft campaign measurements, Atmos. Chem. Phys., 10, 9863–9878, http://dx.doi.org/10.5194/acp-10-9863-2010doi:10.5194/acp-10-9863-2010, 2010.

Stephens, M. A.: EDF Statistics for Goodnes of Fit and Some Comparisons, J. Am. Soc. Stat. Assoc., 69(347), 730–737, 1974.

Stewart, D. J., Taylor, C. M., Reeves, C. E., and McQuaid, J. B.: Biogenic nitrogen oxide emissions from soils: impact on NOx and ozone over west Africa during AMMA (African Monsoon Multidisciplinary Analysis): observational study, Atmos. Chem. Phys., 8, 2285–2297, http://dx.doi.org/10.5194/acp-8-2285-2008doi:10.5194/acp-8-2285-2008, 2008.

Stone, D., Evans, M. J., Commane, R., Ingham, T., Floquet, C. F. A., McQuaid, J. B., Brookes, D. M., Monks, P. S., Purvis, R., Hamilton, J. F., Hopkins, J., Lee, J., Lewis, A. C., Stewart, D., Murphy, J. G., Mills, G., Oram, D., Reeves, C. E., and Heard, D. E.: HOx observations over West Africa during AMMA: impact of isoprene and NOx, Atmos. Chem. Phys., 10, 9415–9429, http://dx.doi.org/10.5194/acp-10-9415-2010doi:10.5194/acp-10-9415-2010, 2010.

Tan, D., Faloona, I., Simpas, J. B., Brune, W., Olson, J., Crawford, J., Avery, M., Sachse, G., Vay, S., Sandholm, S., Guan, H. W., Vaughn, T., Mastromarino, J., Heikes, B., Snow, J., Podolske, J., and Singh, H.: OH and HO2 in the tropical Pacific: Results from PEM-Tropics B, J. Geophys. Res., 106, 32667–32681, 2001.

Thornton, J. A., Wooldridge, P. J., Cohen, R. C., Martinez, M., Harder, H., Brune, W. H., Williams, E. J., Roberts, J. M., Fehsenfeld, F. C., Hall, S. R., Shetter, R. E., Wert, B. P., and Fried, A.: Ozone production rates as a function of NOx abundances and HOx production rates in the Nashville urban plume, J. Geophys. Res., 107, D124146, http://dx.doi.org/10.1029/2001JD000932doi:10.1029/2001JD000932, 2002.

Veyret, B., Lesclaux, R., Rayez, M.-T., Rayez, J.-C., Cox, R. A., and Moortgat, G. K.: Kinetics and Mechanism of the Photooxidation of Formaldehyde. 1. Flash Photolysis Study, J. Phys. Chem., 93, 2368–2374, 1989.

Whalley, L. K., Furneaux, K. L., Goddard, A., Lee, J. D., Mahajan, A., Oetjen, H., Read, K. A., Kaaden, N., Carpenter, L. J., Lewis, A. C., Plane, J. M. C., Saltzman, E. S., Wiedensohler, A., and Heard, D. E.: The chemistry of OH and HO2 radicals in the boundary layer over the tropical Atlantic Ocean, Atmos. Chem. Phys., 10, 1555–1576, http://dx.doi.org/10.5194/acp-10-1555-2010doi:10.5194/acp-10-1555-2010, 2010.

Whalley, L. K., Edwards, P. M., Furneaux, K. L., Goddard, A., Ingham, T., Evans, M. J., Stone, D., Hopkins, J. R., Jones, C. E., Karunaharan, A., Lee, J. D., Lewis, A. C., Monks, P. S., Moller, S. J., and Heard, D. E.: Quantifying the magnitude of a missing hydroxyl radical source in a tropical rainforest, Atmos. Chem. Phys. Discuss., 11, 5785–5809, http://dx.doi.org/10.5194/acpd-11-5785-2011doi:10.5194/acpd-11-5785-2011, 2011.

Wolfe, G. M., Thornton, J. A., Bouvier-Brown, N. C., Goldstein, A. H., Park, J.-H., McKay, M., Matross, D. M., Mao, J., Brune, W. H., LaFranchi, B. W., Browne, E. C., Min, K.-E., Wooldridge, P. J., Cohen, R. C., Crounse, J. D., Faloona, I. C., Gilman, J. B., Kuster, W. C., de Gouw, J. A., Huisman, A., and Keutsch, F. N.: The Chemistry of Atmosphere-Forest Exchange (CAFE) Model – Part 2: Application to BEARPEX-2007 observations, Atmos. Chem. Phys., 11, 1269–1294, http://dx.doi.org/10.5194/acp-11-1269-2011doi:10.5194/acp-11-1269-2011, 2011.