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2017
K. J. Zarzana, K-E. Min, R. A. Washenfelder, J. Kaiser, M. Krawiec-Thayer, J. Peischl, J. A. Neuman, J. B. Nowak, N. L. Wagner, W. P. Dubè, J. M. St. Clair, G. M. Wolfe, T. F. Hanisco, F. N. Keutsch, T. B. Ryerson, and S. S. Brown. 2017. “Emissions of Glyoxal and Other Carbonyl Compounds from Agricultural Biomass Burning Plumes Sampled by Aircraft.” Environmental Science & Technology. Publisher's Version
C. C. Miller, D.J. Jacob, E. A. Marais, K. Yu, K. R. Travis, P. S. Kim, J. A. Fisher, L. Zhu, G. M. Wolfe, F. N. Keutsch, J. Kaiser, K.-E. Min, S. S. Brown, R. A. Washenfelder, G. González Abad, and K. Chance. 2017. “Glyoxal yield from isoprene oxidation and relation to formaldehyde: chemical mechanism, constraints from SENEX aircraft observations, and interpretation of OMI satellite data.” Atmospheric Chemistry and Physics, 2017, 17, Pp. 8725-8738. Publisher's Version
J. Kaiser, D.J. Jacob, L. Zhu, K. R. Travis, J. A. Fisher, G. González Abad, L. Zhang, X. Zhang, A. Fried, J. D. Crounse, J. M. St. Clair, and A. Wisthaler. 2017. “High-resolution inversion of OMI formaldehyde columns to quantify isoprene emission on ecosystem-relevant scales: application to the Southeast US.” Atmospheric Chemistry and Physics Discussions. Publisher's VersionAbstract

Isoprene emissions from vegetation have a large effect on atmospheric chemistry and air quality. ‘Bottom-up’ isoprene emission inventories used in atmospheric models are based on limited vegetation information and uncertain land cover data, leading to potentially large errors. Satellite observations of atmospheric formaldehyde (HCHO), a high-yield product of isoprene oxidation, provide ‘top-down’ information to evaluate isoprene emission inventories through inverse analyses. Past inverse analyses have however been hampered by uncertainty in the HCHO satellite data, uncertainty in the time- and NOx-dependent yield of HCHO from isoprene oxidation, and coarse resolution of the atmospheric models used for the inversion. Here we demonstrate the ability to use HCHO satellite data from the OMI instrument in a high-resolution inversion to constrain isoprene emissions on ecosystem-relevant scales. The inversion uses the adjoint of the GEOS-Chem chemical transport model at 0.25° × 0.3125° horizontal resolution to interpret observations over the Southeast US in August-September 2013. It takes advantage of concurrent NASA SEAC4RS aircraft observations of isoprene and its oxidation products including HCHO to validate the OMI HCHO data over the region, test the GEOS-Chem isoprene oxidation mechanism and NOx environment, and independently evaluate the inversion. This evaluation shows in particular that local model errors in NOx concentrations propagate to biases in inferring isoprene emissions from the HCHO data. It is thus essential to correct model NOx biases, which was done here using SEAC4RS observations but can be done more generally using satellite NO2 data concurrently with HCHO. We find in our inversion that isoprene emissions from the widely-used MEGAN v2.1 inventory are biased high over the Southeast US by 40% on average, although the broad-scale distributions are correct including maximum emissions in Arkansas/Louisiana and high base emission factors in the oak-covered Ozarks of Southeast Missouri. A particularly large discrepancy is in the Edwards Plateau of Central Texas where MEGAN v2.1 is too high by a factor of 3, possibly reflecting errors in land cover. The lower isoprene emissions inferred from our inversion, when implemented into GEOS-Chem, decrease surface ozone over the Southeast US by 1–3 ppb and decrease the isoprene contribution to organic aerosol from 40% to 20%.

M. R. Marvin, G. M. Wolfe, R. J. Salawitch, T. P. Canty, S. J. Roberts, K. R. Travis, K. C. Aikin, J. A. deGouw, M. Graus, T. F. Hanisco, J. S. Holloway, G. Hübler, J. Kaiser, F. N. Keutsch, J. Peischl, I. B. Pollack, J. M. Roberts, T. B. Ryerson, P. R. Veres, and C. Warneke. 2017. “Impact of evolving isoprene mechanisms on simulated formaldehyde: An inter-comparison supported by in situ observations from SENEX.” Atmospheric Environment, 164, Pp. 325 - 336. Publisher's Version
P. M. Edwards, K. C. Aikin, W. P. Dube, J. L. Fry, J. B. Gilman, J. A. deGouw, M. G. Graus, T. F. Hanisco, J. Holloway, G. Huber, J. Kaiser, F. N. Keutsch, B. M. Lerner, J. A. Neuman, D. D. Parrish, J. Peischl, I. B. Pollack, A. R. Ravishankara, J. M. Roberts, T. B. Ryerson, M. Trainer, P. R. Veres, G. M. Wolfe, C. Warneke, and S. S. Brown. 2017. “Transition from high- to low-NOx control of night-time oxidation in the southeastern US.” Nature Geoscience, 10, 7, Pp. 490+.Abstract
The influence of nitrogen oxides (NOx) on daytime atmospheric oxidation cycles is well known, with clearly defined high-and low-NOx regimes. During the day, oxidation reactions-which contribute to the formation of secondary pollutants such as ozone-are proportional to NOx at low levels, and inversely proportional to NOx at high levels. Night-time oxidation of volatile organic compounds also influences secondary pollutants but lacks a similar clear definition of high-and low-NOx regimes, even though such regimes exist. Decreases in anthropogenic NOx emissions in the US and Europe coincided with increases in Asia over the last 10 to 20 years, and have altered both daytime and nocturnal oxidation cycles. Here we present measurements of chemical species in the lower atmosphere from day-and night-time research flights over the southeast US in 1999 and 2013, supplemented by atmospheric chemistry simulations. We find that night-time oxidation of biogenic volatile organic compounds (BVOC) is NOx-limited when the ratio of NOx to BVOC is below approximately 0.5, and becomes independent of NOx at higher ratios. The night-time ratio of NOx to BVOC in 2013 averaged 0.6 aloft. We suggest that night-time oxidation in the southeast US is in transition between NOx-dominated and ozone-dominated.
2016
C. Warneke, M. Trainer, J. A. deGouw, D. D. Parrish, D. W. Fahey, A. R. Ravishankara, A. M. Middlebrook, C. A. Brock, J. M. Roberts, S. S. Brown, J. A. Neuman, B. M. Lerner, D. Lack, D. Law, G. Hübler, I. Pollack, S. Sjostedt, T. B. Ryerson, J. B. Gilman, J. Liao, J. Holloway, J. Peischl, J. B. Nowak, K. C. Aikin, K.-E. Min, R. A. Washenfelder, M. G. Graus, M. Richardson, M. Z. Markovic, N. L. Wagner, A. Welti, P. R. Veres, P. Edwards, J. P. Schwarz, T. Gordon, W. P. Dube, S. A. McKeen, J. Brioude, R. Ahmadov, A. Bougiatioti, J. J. Lin, A. Nenes, G. M. Wolfe, T. F. Hanisco, B. H. Lee, F. D. Lopez-Hilfiker, J. A. Thornton, F. N. Keutsch, J. Kaiser, J. Mao, and C. D. Hatch. 2016. “Instrumentation and measurement strategy for the NOAA SENEX aircraft campaign as part of the Southeast Atmosphere Study 2013.” Atmospheric Measurement Techniques, 9, 7, Pp. 3063–3093. Publisher's Version
G. M. Wolfe, J. Kaiser, T. F. Hanisco, F. N. Keutsch, J. A. deGouw, J. B. Gilman, M. Graus, C. D. Hatch, J. Holloway, L. W. Horowitz, B. H. Lee, B. M. Lerner, F. Lopez-Hilifiker, J. Mao, M. R. Marvin, J. Peischl, I. B. Pollack, J. M. Roberts, T. B. Ryerson, J. A. Thornton, P. R. Veres, and C. Warneke. 2016. “Formaldehyde production from isoprene oxidation across NOx regimes.” Atmospheric Chemistry and Physics, 16, 4, Pp. 2597–2610. Publisher's Version
J. Li, J. Mao, K-E. Min, R. A. Washenfelder, S. S. Brown, J. Kaiser, F. N. Keutsch, R. Volkamer, G. M. Wolfe, T. F. Hanisco, I. B. Pollack, T. B. Ryerson, Martin G., J. B. Gilman, B. M. Lerner, Carsten W., J. A. deGouw, A. M. Middlebrook, J. Liao, A. Welti, B. H. Henderson, V. F. McNeill, S. R. Hall, K. Ullmann, L. J. Donner, F. Paulot, and L. W. Horowitz. 2016. “Observational constraints on glyoxal production from isoprene oxidation and its contribution to organic aerosol over the Southeast United States.” Journal of Geophysical Research: Atmospheres, 121, 16, Pp. 9849–9861. Publisher's Version
J. Kaiser, K. M. Skog, K. Baumann, S. B. Bertman, S. B. Brown, W. H. Brune, J. D. Crounse, J. A. deGouw, E. S. Edgerton, P. A. Feiner, A. H. Goldstein, A. Koss, P. K. Misztal, T. B. Nguyen, K. F. Olson, J. M. St. Clair, A. P. Teng, S. Toma, P. O. Wennberg, R. J. Wild, L. Zhang, and F. N. Keutsch. 2016. “Speciation of OH reactivity above the canopy of an isoprene-dominated forest.” Atmospheric Chemistry and Physics, 16, 14, Pp. 9349–9359. Publisher's VersionAbstract
Measurements of OH reactivity, the inverse lifetime of the OH radical, can provide a top–down estimate of the total amount of reactive carbon in an air mass. Using a comprehensive measurement suite, we examine the measured and modeled OH reactivity above an isoprene-dominated forest in the southeast United States during the 2013 Southern Oxidant and Aerosol Study (SOAS) field campaign. Measured and modeled species account for the vast majority of average daytime reactivity (80–95 %) and a smaller portion of nighttime and early morning reactivity (68–80 %). The largest contribution to total reactivity consistently comes from primary biogenic emissions, with isoprene contributing ∼  60 % in the afternoon, and ∼  30–40 % at night and monoterpenes contributing ∼  15–25 % at night. By comparing total reactivity to the reactivity stemming from isoprene alone, we find that ∼  20 % of the discrepancy is temporally related to isoprene reactivity, and an additional constant ∼  1 s−1 offset accounts for the remaining portion. The model typically overestimates measured OVOC concentrations, indicating that unmeasured oxidation products are unlikely to influence measured OH reactivity. Instead, we suggest that unmeasured primary emissions may influence the OH reactivity at this site.
2015
J. A. deGouw, S. A. McKeen, K. C. Aikin, C. A. Brock, S. S. Brown, J. B. Gilman, M. Graus, T. Hanisco, J. S. Holloway, J. Kaiser, F. N. Keutsch, B. M. Lerner, J. Liao, M. Z. Markovic, A. M. Middlebrook, K.-E. Min, J. A. Neuman, J. B. Nowak, J. Peischl, I. B. Pollack, J. M. Roberts, T. B. Ryerson, M. Trainer, P. R. Veres, C. Warneke, A. Welti, and G. M. Wolfe. 2015. “Airborne measurements of the atmospheric emissions from a fuel ethanol refinery.” Journal of Geophysical Research: Atmospheres, 120, 9, Pp. 4385–4397. Publisher's Version
J. Kaiser, G. M. Wolfe, B. Bohn, S. Broch, H. Fuchs, L. N. Ganzeveld, S. Gomm, R. Häseler, A. Hofzumahaus, F. Holland, J. Jäger, X. Li, I. Lohse, K. Lu, A. S. H. Prévôt, F. Rohrer, R. Wegener, R. Wolf, T. F. Mentel, A. Kiendler-Scharr, A. Wahner, and F. N. Keutsch. 2015. “Evidence for an unidentified non-photochemical ground-level source of formaldehyde in the Po Valley with potential implications for ozone production.” Atmospheric Chemistry and Physics, 15, 3, Pp. 1289–1298. Publisher's VersionAbstract

Ozone concentrations in the Po Valley of northern Italy often exceed international regulations. As both a source of radicals and an intermediate in the oxidation of most volatile organic compounds (VOCs), formaldehyde (HCHO) is a useful tracer for the oxidative processing of hydrocarbons that leads to ozone production. We investigate the sources of HCHO in the Po Valley using vertical profile measurements acquired from the airship Zeppelin NT over an agricultural region during the PEGASOS 2012 campaign. Using a 1-D model, the total VOC oxidation rate is examined and discussed in the context of formaldehyde and ozone production in the early morning. While model and measurement discrepancies in OH reactivity are small (on average 3.4 ± 13%), HCHO concentrations are underestimated by as much as 1.5 ppb (45%) in the convective mixed layer. A similar underestimate in HCHO was seen in the 2002–2003 FORMAT Po Valley measurements, though the additional source of HCHO was not identified. Oxidation of unmeasured VOC precursors cannot explain the missing HCHO source, as measured OH reactivity is explained by measured VOCs and their calculated oxidation products. We conclude that local direct emissions from agricultural land are the most likely source of missing HCHO. Model calculations demonstrate that radicals from degradation of this non-photochemical HCHO source increase model ozone production rates by as much as 0.6 ppb h−1 (12%) before noon.
J. Kaiser, G. M. Wolfe, K. E. Min, S. S. Brown, C. C. Miller, D.J. Jacob, J. A. deGouw, M. Graus, T. F. Hanisco, J. Holloway, J. Peischl, I. B. Pollack, T. B. Ryerson, C. Warneke, R. A. Washenfelder, and F. N. Keutsch. 2015. “Reassessing the ratio of glyoxal to formaldehyde as an indicator of hydrocarbon precursor speciation.” Atmospheric Chemistry and Physics, 15, 13, Pp. 7571–7583. Publisher's VersionAbstract
The yield of formaldehyde (HCHO) and glyoxal (CHOCHO) from oxidation of volatile organic compounds (VOCs) depends on precursor VOC structure and the concentration of NOx (NOx = NO + NO2). Previous work has proposed that the ratio of CHOCHO to HCHO (RGF) can be used as an indicator of precursor VOC speciation, and absolute concentrations of the CHOCHO and HCHO as indicators of NOx. Because this metric is measurable by satellite, it is potentially useful on a global scale; however, absolute values and trends in RGF have differed between satellite and ground-based observations. To investigate potential causes of previous discrepancies and the usefulness of this ratio, we present measurements of CHOCHO and HCHO over the southeastern United States (SE US) from the 2013 SENEX (Southeast Nexus) flight campaign, and compare these measurements with OMI (Ozone Monitoring Instrument) satellite retrievals. High time-resolution flight measurements show that high RGF is associated with monoterpene emissions, low RGF is associated with isoprene oxidation, and emissions associated with oil and gas production can lead to small-scale variation in regional RGF. During the summertime in the SE US, RGF is not a reliable diagnostic of anthropogenic VOC emissions, as HCHO and CHOCHO production are dominated by isoprene oxidation. Our results show that the new CHOCHO retrieval algorithm reduces the previous disagreement between satellite and in situ RGF observations. As the absolute values and trends in RGF observed during SENEX are largely reproduced by OMI observations, we conclude that satellite-based observations of RGF can be used alongside knowledge of land use as a global diagnostic of dominant hydrocarbon speciation.
2014
J. C. Rivera-Rios, T. B. Nguyen, J. D. Crounse, W. Jud, J. M. St. Clair, T. Mikoviny, J. B. Gilman, B. M. Lerner, J. B. Kaiser, J. de Gouw, A. Wisthaler, A. Hansel, P. O. Wennberg, J. H. Seinfeld, and F. N. Keutsch. 2014. “Conversion of hydroperoxides to carbonyls in field and laboratory instrumentation: Observational bias in diagnosing pristine versus anthropogenically controlled atmospheric chemistry.” Geophysical Research Letters, 41, 23, Pp. 8645–8651. Publisher's Version
J. Kaiser, X. Li, R. Tillmann, I. Acir, F. Holland, F. Rohrer, R. Wegener, and F. N. Keutsch. 2014. “Intercomparison of Hantzsch and fiber-laser-induced-fluorescence formaldehyde measurements.” Atmospheric Measurement Techniques, 7, 6, Pp. 1571–1580. Publisher's VersionAbstract
Two gas-phase formaldehyde (HCHO) measurement techniques, a modified commercial wet-chemical instrument based on Hantzsch fluorimetry and a custom-built instrument based on fiber laser-induced fluorescence (FILIF), were deployed at the atmospheric simulation chamber SAPHIR (Simulation of Atmospheric PHotochemistry In a large Reaction Chamber) to compare the instruments' performances under a range of conditions. Thermolysis of para-HCHO and ozonolysis of 1-butene were used as HCHO sources, allowing for calculations of theoretical HCHO mixing ratios. Calculated HCHO mixing ratios are compared to measurements, and the two measurements are also compared. Experiments were repeated under dry and humid conditions (RH < 2% and RH > 60%) to investigate the possibility of a water artifact in the FILIF measurements. The ozonolysis of 1-butene also allowed for the investigation of an ozone artifact seen in some Hantzsch measurements in previous intercomparisons. Results show that under all conditions the two techniques are well correlated (R2 ≥ 0.997), and linear regression statistics show measurements agree with within stated uncertainty (15% FILIF + 5% Hantzsch). No water or ozone artifacts are identified. While a slight curvature is observed in some Hantzsch vs. FILIF regressions, the potential for variable instrument sensitivity cannot be attributed to a single instrument at this time. Measurements at low concentrations highlight the need for a secondary method for testing the purity of air used in instrument zeroing and the need for further FILIF White cell outgassing experiments.
Xin L., F. Rohrer, A. Hofzumahaus, T. Brauers, R. Häseler, B. Bohn, S. Broch, H. Fuchs, S. Gomm, F. Holland, J. Jäger, J. Kaiser, F. N. Keutsch, I. Lohse, K. Lu, R. Tillmann, R. Wegener, G. M. Wolfe, T. F. Mentel, A. Kiendler-Scharr, and A. Wahner. 2014. “Missing Gas-Phase Source of HONO Inferred from Zeppelin Measurements in the Troposphere.” Science, 344, 6181, Pp. 292–296. Publisher's VersionAbstract
Nitrous acid (HONO) is an important atmospheric trace gas that acts as a precursor of tropospheric hydroxyl-radicals (OH), which is responsible for the self-cleansing capacity of the atmosphere and which also controls the concentrations of greenhouse gases, such as methane and ozone. How HONO is made is a mystery. Flying onboard a Zeppelin over the Po Valley in Northern Italy, Li et al. (p. 292) discovered HONO in the undisturbed morning troposphere, indicating that HONO must be produced there, rather than mixed from the surface. The high HONO concentrations are likely to have been formed by a light-dependent gas-phase source that probably consumed OH or HO2 radicals, which hints that the impact of HONO on the abundance of OH in the entire troposphere may be substantially overestimated. Gaseous nitrous acid (HONO) is an important precursor of tropospheric hydroxyl radicals (OH). OH is responsible for atmospheric self-cleansing and controls the concentrations of greenhouse gases like methane and ozone. Due to lack of measurements, vertical distributions of HONO and its sources in the troposphere remain unclear. Here, we present a set of observations of HONO and its budget made onboard a Zeppelin airship. In a sunlit layer separated from Earth’s surface processes by temperature inversion, we found high HONO concentrations providing evidence for a strong gas-phase source of HONO consuming nitrogen oxides and potentially hydrogen oxide radicals. The observed properties of this production process suggest that the generally assumed impact of HONO on the abundance of OH in the troposphere is substantially overestimated.