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Chemical Reviews 04/2013; · 40.20 Impact Factor
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H.-P. Dorn,
R. L. Apodaca,
S. M. Ball,
T. Brauers,
S. S. Brown, R. C. Cohen,
J. N. Crowley,
W. P. Dubé,
J. L. Fry,
H. Fuchs, [......],
A. A. Ruth,
E. Schlosser,
G. Schuster,
A. J. L. Shillings,
W. R. Simpson,
J. Thieser,
D. S. Venables,
A. Wahner,
R. Wegener,
P. J. Wooldridge
[show abstract]
[hide abstract]
ABSTRACT: The detection of atmospheric NO3 radicals is still challenging owing to its low mixing
ratios (�1 to 300 pptv) in the troposphere. While long-path differential optical absorption
spectroscopy (DOAS) is a well established NO3 detection approach for over 25 yr,
5 newly sensitive techniques have been developed in the past decade. This publication
outlines the results of the first comprehensive intercomparison of seven instruments
developed for the spectroscopic detection of tropospheric NO3. Four instruments were
based on cavity ring-down spectroscopy (CRDS), two utilised open-path cavity enhanced
absorption spectroscopy (CEAS), and one applied “classical” long-path DOAS.
10 The intercomparison campaign “NO3Comp” was held at the atmosphere simulation
chamber SAPHIR in J¨ ulich (Germany) in June 2007. Twelve experiments were performed
in the well mixed chamber for variable concentrations of NO3, N2O5, NO2, hydrocarbons,
and water vapour, in the absence and in the presence of inorganic or
organic aerosol. The overall precision of the cavity instruments varied between 0.5 and
15 5 pptv for integration times of 1 s to 5min; that of the DOAS instrument was 9 pptv for an
acquisition time of 1 min. The NO3 data of all instruments correlated excellently with the
NOAA-CRDS instrument, which was selected as the common reference because of its
superb sensitivity, high time resolution, and most comprehensive data coverage. The
median of the coefficient of determination (r2) over all experiments of the campaign (60
20 correlations) is r2 =0.981 (25th/75th percentiles: 0.949/0.994; min/max: 0.540/0.999).
The linear regression analysis of the campaign data set yielded very small intercepts
(1.2±5.3 pptv) and the average slope of the regression lines was close to unity (1.02,
min: 0.72, max: 1.36). The deviation of individual regression slopes from unity was
always within the combined accuracies of each instrument pair. The very good cor-
respondence between the NO3 measurements by all instruments for aerosol-free experiments
indicates that the losses of NO3 in the inlet of the instruments were determined
reliably by the participants for the corresponding conditions. In the presence of
inorganic or organic aerosol, however, differences in the measured NO3 mixing ratios were detectable among the instruments. In individual experiments the discrepancies
increased with time, pointing to additional NO3 radical losses by aerosol deposited
onto the inlet walls of the instruments. Instruments using DOAS analyses showed no
significant effect of aerosol on the detection of NO3. No hint of a cross interference of
NO2 5 was found. The effect of non-Lambert–Beer behaviour of water vapour absorption
lines on the accuracy of the NO3 detection by broadband techniques was small
and well controlled. The NO3Comp campaign demonstrated the high quality, reliability
and robustness of performance of current state-of-the-art instrumentation for NO3
detection.
AMTD. 01/2013; 6:303-279.
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A W Rollins,
E C Browne,
K-E Min,
S E Pusede,
P J Wooldridge,
D R Gentner,
A H Goldstein,
S Liu,
D A Day,
L M Russell, R C Cohen
[show abstract]
[hide abstract]
ABSTRACT: Laboratory studies have established a number of chemical pathways by which nitrogen oxides (NO(x)) affect atmospheric organic aerosol (OA) production. However, these effects have not been directly observed in ambient OA. We report measurements of particulate organic nitrates in Bakersfield, California, the nighttime formation of which increases with NO(x) and is suppressed by high concentrations of organic molecules that rapidly react with nitrate radical (NO(3))--evidence that multigenerational chemistry is responsible for organic nitrate aerosol production. This class of molecules represents about a third of the nighttime increase in OA, suggesting that most nighttime secondary OA is due to the NO(3) product of anthropogenic NO(x) emissions. Consequently, reductions in NO(x) emissions should reduce the concentration of organic aerosol in Bakersfield and the surrounding region.
Science 09/2012; 337(6099):1210-2. · 31.20 Impact Factor
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M R Beaver,
St. J M Clair,
F Paulot,
K M Spencer,
J D Crounse,
B W LaFranchi,
K E Min,
S E Pusede,
P J Wooldridge,
G W Schade,
C Park, R C Cohen,
P O Wennberg
Atmospheric Chemistry and Physics. 01/2012; 12(13):5773-5785.
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Atmospheric Chemistry and Physics 11/2011; 11(22):11647-11655.
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Atmospheric Measurement Techniques 09/2011; 4(9):1929-1935. · 3.34 Impact Factor
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Atmospheric Measurement Techniques Discussions. 03/2011; 4(2):1989-2005.
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Fried,
C Cantrell,
J Olson,
J H Crawford,
P Weibring,
J Walega,
D Richter,
W Junkermann,
R Volkamer,
R Sinreich, [......],
R E Shetter,
S R Hall,
K Ullmann,
W H Brune,
J Mao,
X Ren,
L G Huey,
H B Singh,
J W Hair,
D Riemer
Atmospheric Chemistry and Physics 03/2011; 11(3):9887-9957. · 4.88 Impact Factor
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A. J. Huisman,
J. R. Hottle,
M. M. Galloway,
J. P. DiGangi,
K. L. Coens,
W. Choi,
I. C. Faloona,
J. B. Gilman,
W. C. Kuster,
J. Gouw de, [......], R. C. Cohen,
G. M. Wolfe,
J. A. Thornton,
K. S. Docherty,
D. K. Farmer,
M. J. Cubison,
J. L. Jimenez,
J. Mao,
W. H. Brune,
F. N. Keutsch
Atmos. Chem. Phys. 01/2011; 11(17):8883-8897.
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G. M. Wolfe,
J. A. Thornton,
N. C. Bouvier-Brown,
A. H. Goldstein,
J. -H. Park,
M. McKay,
D. M. Matross,
J. Mao,
W. H. Brune,
B. W. LaFranchi, [......],
K. -E. Min,
P. J. Wooldridge, R. C. Cohen,
J. D. Crounse,
I. C. Faloona,
J. B. Gilman,
W. C. Kuster,
J. A. Gouw de,
A. Huisman,
F. N. Keutsch
Atmos. Chem. Phys. 01/2011; 11(3):1269-1294.
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[show abstract]
[hide abstract]
ABSTRACT: We use observations of fire radiative power (FRP) from the Moderate Resolution Imaging Spectroradiometer (MODIS) and tropospheric NO2 column measurements from the Ozone Monitoring Instrument (OMI) to derive NO2 wildfire emission coefficients (g MJ−1) for three land types over California and Nevada. Retrieved emission coefficients were 0.279 ± 0.077, 0.342 ± 0.053, and 0.696 ± 0.088 g MJ−1 NO2 for forest, grass and shrub fuels, respectively. These emission coefficients reproduce ratios of emissions with fuel type reported previously using independent methods. However, the magnitude of these coefficients is lower than prior estimates, which suggests either a negative bias in the OMI NO2 retrieval over regions of active emissions, or that the average fire observed in our study has a smaller ratio of flaming to smoldering combustion than measurements used in prior estimates of emissions. Our results indicate that satellite data can provide an extensive characterization of the variability in fire NOx emissions; 67% of the variability in emissions in this region can be accounted for using an FRP-based parameterization.
Atmospheric Chemistry and Physics Discussions. 01/2011;
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[show abstract]
[hide abstract]
ABSTRACT: Observations of NOx in the Sacramento, CA region show that mixing ratios decreased by 30% between 2001 and 2008. Here we use an observation-based method to quantify net ozone production rates in the outflow from the Sacramento metropolitan region and examine the O3 decrease resulting from reductions in NOx emissions. This observational method does not rely on assumptions about detailed chemistry of ozone production, rather it is an independent means to verify and test these assumptions. We use an instantaneous steady-state model as well as a detailed 1-D plume model to aid in interpretation of the ozone production inferred from observations. In agreement with the models, the observations show that early in the plume, the NOx dependence for Ox (Ox = O3 + NO2) production is strongly coupled with temperature, suggesting that temperature-dependent biogenic VOC emissions can drive Ox production between NOx-limited and NOx-suppressed regimes. As a result, NOx reductions were found to be most effective at higher temperatures over the 7 year period. We show that violations of the California 1-hour O3 standard (90 ppb) in the region have been decreasing linearly with decreases in NOx (at a given temperature) and predict that reductions of NOx concentrations (and presumably emissions) by an additional 30% (relative to 2007 levels) will eliminate violations of the state 1 h standard in the region. If current trends continue, a 30% decrease in NOx is expected by 2012, and an end to violations of the 1 h standard in the Sacramento region appears to be imminent.
Atmospheric Chemistry and Physics Discussions. 01/2011;
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G. M. Wolfe,
J. A. Thornton,
N. C. Bouvier-Brown,
A. H. Goldstein,
Park J.-H,
McKay M,
D. M. Matross,
Mao J,
W. H. Brune,
B. W. LaFranchi, [......],
Min K.-E,
P. J. Wooldridge, R. C. Cohen,
J. D. Crounse,
I. C. Faloona,
J. B. Gilman,
W. C. Kuster,
J. A. de Gouw,
Huisman A,
F. N. Keutsch
[show abstract]
[hide abstract]
ABSTRACT: In a companion paper, we introduced the Chemistry of Atmosphere-Forest Exchange (CAFE) model, a vertically-resolved 1-D chemical transport model designed to probe the details of near-surface reactive gas exchange. Here, we apply CAFE to noontime observations from the 2007 Biosphere Effects on Aerosols and Photochemistry Experiment (BEARPEX-2007). In this work we evaluate the CAFE modeling approach, demonstrate the significance of in-canopy chemistry for forest-atmosphere exchange and identify key shortcomings in the current understanding of intra-canopy processes. CAFE generally reproduces BEARPEX-2007 observations but requires an enhanced radical recycling mechanism to overcome a factor of 6 underestimate of hydroxyl (OH) concentrations observed during a warm (~29 °C) period. Modeled fluxes of acyl peroxy nitrates (APN) are quite sensitive to gradients in chemical production and loss, demonstrating that chemistry may perturb forest-atmosphere exchange even when the chemical timescale is long relative to the canopy mixing timescale. The model underestimates peroxy acetyl nitrate (PAN) fluxes by 50% and the exchange velocity by nearly a factor of three under warmer conditions, suggesting that near-surface APN sinks are underestimated relative to the sources. Nitric acid typically dominates gross dry N deposition at this site, though other reactive nitrogen (NOy) species can comprise up to 28% of the N deposition budget under cooler conditions. Upward NO2 fluxes cause the net above-canopy NOy flux to be ~30% lower than the gross depositional flux. CAFE under-predicts ozone fluxes and exchange velocities by ~20%. Large uncertainty in the parameterization of cuticular and ground deposition precludes conclusive attribution of non-stomatal fluxes to chemistry or surface uptake. Model-measurement comparisons of vertical concentration gradients for several emitted species suggests that the lower canopy airspace may be only weakly coupled with the upper canopy. Future efforts to model forest-atmosphere exchange will require a more mechanistic understanding of non-stomatal deposition and a more thorough characterization of in-canopy mixing processes.
Atmospheric Chemistry and Physics. 01/2011;
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E. C. Browne,
A. E. Perring,
P. J. Wooldridge,
Apel E,
S. R. Hall,
L. G. Huey,
Mao J,
K. M. Spencer,
J. M. St. Clair,
A. J. Weinheimer,
Wisthaler A, R. C. Cohen
[show abstract]
[hide abstract]
ABSTRACT: Using measurements from the NASA Arctic Research of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS) experiment, we show that methyl peroxy nitrate (CH3O2NO2) is present in concentrations of ~5–15 pptv in the springtime arctic upper troposphere. We investigate the regional and global effects of CH3O2NO2 by including its chemistry in the GEOS-CHEM 3-D global chemical transport model. We find that at temperatures below 240 K inclusion of CH3O2NO2 chemistry results in decreases of up to ~20% in NOx, ~20% in N2O5, ~5% in HNO3, ~2% in ozone, and increases in methyl hydrogen peroxide of up to ~14%. Larger changes are observed in biomass burning plumes lofted to high altitude. Additionally, by sequestering NOx at low temperatures, CH3O2NO2 decreases the cycling of HO2 to OH, resulting in a larger upper tropospheric HO2 to OH ratio. These results may impact some estimates of lightning NOx sources as well as help explain differences between models and measurements of upper tropospheric composition.
Atmospheric Chemistry and Physics Discussions. 01/2011;
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J L Fry,
A Kiendler-Scharr,
A W Rollins,
T Brauers,
S S Brown,
H.-P Dorn,
W P Dubé,
H Fuchs,
A Mensah,
F Rohrer,
R Tillmann,
A Wahner,
P J Wooldridge, R C Cohen
[show abstract]
[hide abstract]
ABSTRACT: The formation of organic nitrates and sec-ondary organic aerosol (SOA) were monitored during the NO 3 + limonene reaction in the atmosphere simulation chamber SAPHIR at Research Center Jülich. The 24-h run began in a purged, dry, particle-free chamber and com-prised two injections of limonene and oxidants, such that the first experiment measured SOA yield in the absence of seed aerosol, and the second experiment yields in the pres-ence of 10 µg m −3 seed organic aerosol. After each injection, two separate increases in aerosol mass were observed, corre-sponding to sequential oxidation of the two limonene double bonds. Analysis of the measured NO 3 , limonene, product ni-trate concentrations, and aerosol properties provides mech-anistic insight and constrains rate constants, branching ra-tios and vapor pressures of the products. The organic ni-trate yield from NO 3 + limonene is ≈30%. The SOA mass yield was observed to be 25–40%. The first injection is re-produced by a kinetic model. PMF analysis of the aerosol composition suggests that much of the aerosol mass results from combined oxidation by both O 3 and NO 3 , e.g., oxida-tion of NO 3 + limonene products by O 3 . Further, later aerosol nitrate mass seems to derive from heterogeneous uptake of NO 3 onto unreacted aerosol alkene.
Atmos. Chem. Phys. 01/2011; 11:3879-3894.
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[show abstract]
[hide abstract]
ABSTRACT: We present a new retrieval of tropospheric NO 2 vertical column density from the Ozone Monitoring Instrument (OMI) based on high spatial and temporal resolution terrain and profile inputs. We find non-negligible impacts on the retrieved NO 2 column for ter-rain pressure (±20%), albedo (±40%), and NO 2 vertical profile (−75%–+10%). We 5 compare our NO 2 product, the Berkeley High-Resolution (BEHR) product, with oper-ational retrievals and find that the operational retrievals are biased high (30%) over remote areas and biased low (8%) over urban regions. We validate the operational and BEHR products using boundary layer aircraft observations from the Arctic Re-search of the Composition of the Troposphere from Aircraft and Satellites (ARCTAS-10 CA) field campaign which occurred in June 2008 in California. Results indicate that columns derived using our boundary layer extrapolation method show good agreement with satellite observations (R 2 = 0.65–0.83; N = 68) and provide a more robust valida-tion of satellite-observed NO 2 column than those determined using full vertical spirals (R 2 = 0.26; N = 5) as in previous work. Agreement between aircraft observations and 15 the BEHR product (R 2 = 0.83) is better than agreement with the operational products (R 2 = 0.65–0.72). We also show that agreement between satellite and aircraft observa-tions for all products can be further improved (e.g. BEHR: R 2 = 0.91) using cloud infor-mation from the Moderate Resolution Imaging Spectroradiometer (MODIS) instrument instead of the OMI cloud product. These results indicate that much of the variance 20 in the operational products can be attributed to coarse resolution terrain and profile parameters.
ACPD Chem. Phys. Discuss. 01/2011; 11(11):12411-12440.
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A Fried,
C Cantrell,
J Olson,
J H Crawford,
P Weibring,
J Walega,
D Richter,
W Junkermann,
R Volkamer,
R Sinreich, [......],
K Ullmann,
W H Brune,
J Mao,
X Ren,
L G Huey,
H B Singh,
J W Hair,
D Riemer,
G Diskin,
G Sachse
Atmospheric Chemistry and Physics 01/2011; 11(22):11867-11894.
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H. Fuchs,
S. M. Ball,
B. Bohn,
T. Brauers, R. C. Cohen,
H. P. Dorn,
W. P. Dubé,
J. L. Fry,
R. Häseler,
U. Heitmann, [......],
E. Schlosser,
A. J. L. Shillings,
R. Tillmann,
R. M. Varma,
D. S. Venables,
G. V. Tapia,
A. Wahner,
R. Wegener,
P. J. Wooldridge,
S. S. Brown
[show abstract]
[hide abstract]
ABSTRACT: NO2 concentrations were measured by various instruments during the NO3Comp campaign at the atmosphere simulation chamber SAPHIR at Forschungszentrum Julich, Germany, in June 2007. Analytical methods included photolytic conversion with chemiluminescence (PC-CLD), broadband cavity ring-down spectroscopy (BBCRDS), pulsed cavity ring-down spectroscopy (CRDS), incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS), and laser-induced fluorescence (LIF). All broadband absorption spectrometers were optimized for the detection of the main target species of the campaign, NO3, but were also capable of detecting NO2 simultaneously with reduced sensitivity. NO2 mixing ratios in the chamber were within a range characteristic of polluted, urban conditions, with a maximum mixing ratio of approximately 75 ppbv. The overall agreement between measurements of all instruments was excellent. Linear fits of the combined data sets resulted in slopes that differ from unity only within the stated uncertainty of each instrument. Possible interferences from species such as water vapor and ozone were negligible under the experimental conditions.
Atmospheric Measurement Techniques 01/2010; 3:21-37. · 3.34 Impact Factor
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Ren X,
Gao H,
Zhou X,
J. D. Crounse,
P. O. Wennberg,
E. C. Browne,
B. W. LaFranchi, R. C. Cohen,
McKay M,
A. H. Goldstein,
Mao J
Atmospheric Chemistry and Physics. 01/2010;
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Mao J,
D. J. Jacob,
M J Evans,
J. R. Olson,
Ren X,
W. H. Brune,
J. M. S. Clair,
J. D. Crounse,
K. M. Spencer,
M. R. Beaver, [......],
S. R. Hall,
A. J. Weinheimer, R. C. Cohen,
Chen G,
J. H. Crawford,
Jaeglé L,
J. A. Fisher,
R.M. Yantosca,
P. Le Sager,
Carouge C
[show abstract]
[hide abstract]
ABSTRACT: We use observations from the April~2008 NASA ARCTAS aircraft campaign to the North American Arctic, interpreted with a global 3-D chemical transport model (GEOS-Chem), to better understand the sources and cycling of hydrogen oxide radicals (HO<sub>x</sub>≡H+OH+peroxy radicals) and their reservoirs (HO<sub>y</sub>≡HO<sub>x</sub>+peroxides) in the springtime Arctic atmosphere. We find that a standard gas-phase chemical mechanism overestimates the observed HO<sub>2</sub> and H<sub>2</sub>O<sub>2</sub> concentrations. Computation of HO<sub>x</sub> and HO<sub>y</sub> gas-phase chemical budgets on the basis of the aircraft observations also indicates a large missing sink for both. We hypothesize that this could reflect HO<sub>2</sub> uptake by aerosols, favored by low temperatures and relatively high aerosol loadings, through a mechanism that does not produce H<sub>2</sub>O<sub>2</sub>. Such a mechanism could involve HO<sub>2</sub> aqueous-phase reaction with sulfate (58% of the ARCTAS submicron aerosol by mass) to produce peroxymonosulfate (HSO<sub>5</sub><sup>−</sup>) that would eventually convert back to sulfate and return water. We implemented such an uptake of HO<sub>2</sub> by aerosol in the model using a standard reactive uptake coefficient parameterization with γ(HO<sub>2</sub>) values ranging from 0.02 at 275 K to 0.5 at 220 K. This successfully reproduces the concentrations and vertical distributions of the different HO<sub>x</sub> species and HO<sub>y</sub> reservoirs. HO<sub>2</sub> uptake by aerosol is then a major HO<sub>x</sub> and HO<sub>y</sub> sink, decreasing mean OH and HO<sub>2</sub> concentrations in the Arctic troposphere by 48% and 45% respectively. Circumpolar budget analysis in the model shows that transport of peroxides from northern mid-latitudes contributes 50% of the HO<sub>y</sub> source above 6 km, and cloud chemistry and deposition of H<sub>2</sub>O<sub>2</sub> account together for 40% of the HO<sub>y</sub> sink below 3 km. Better rate and product data for HO<sub>2</sub> uptake by aerosol are needed to understand this role of aerosols in limiting the oxidizing power of the Arctic atmosphere.
Atmospheric Chemistry and Physics Discussions. 01/2010;
