scholarly journals Isoprene and monoterpene fluxes from Central Amazonian rainforest inferred from tower-based and airborne measurements, and implications on the atmospheric chemistry and the local carbon budget

2007 ◽  
Vol 7 (11) ◽  
pp. 2855-2879 ◽  
Author(s):  
U. Kuhn ◽  
M. O. Andreae ◽  
C. Ammann ◽  
A. C. Araújo ◽  
E. Brancaleoni ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Reasonable Agreement ◽  
Carbon Budget ◽  
Eddy Correlation ◽  
Oh Radicals ◽  
Model Calculations ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Budget Analysis ◽  
Vertical Gradients

Abstract. We estimated the isoprene and monoterpene source strengths of a pristine tropical forest north of Manaus in the central Amazon Basin using three different micrometeorological flux measurement approaches. During the early dry season campaign of the Cooperative LBA Airborne Regional Experiment (LBA-CLAIRE-2001), a tower-based surface layer gradient (SLG) technique was applied simultaneously with a relaxed eddy accumulation (REA) system. Airborne measurements of vertical profiles within and above the convective boundary layer (CBL) were used to estimate fluxes on a landscape scale by application of the mixed layer gradient (MLG) technique. The mean daytime fluxes of organic carbon measured by REA were 2.1 mg C m−2 h−1 for isoprene, 0.20 mg C m−2 h−1 for α-pinene, and 0.39 mg C m−2 h−1 for the sum of monoterpenes. These values are in reasonable agreement with fluxes determined with the SLG approach, which exhibited a higher scatter, as expected for the complex terrain investigated. The observed VOC fluxes are in good agreement with simulations using a single-column chemistry and climate model (SCM). In contrast, the model-derived mixing ratios of VOCs were by far higher than observed, indicating that chemical processes may not be adequately represented in the model. The observed vertical gradients of isoprene and its primary degradation products methyl vinyl ketone (MVK) and methacrolein (MACR) suggest that the oxidation capacity in the tropical CBL is much higher than previously assumed. A simple chemical kinetics model was used to infer OH radical concentrations from the vertical gradients of (MVK+MACR)/isoprene. The estimated range of OH concentrations during the daytime was 3–8×106 molecules cm−3, i.e., an order of magnitude higher than is estimated for the tropical CBL by current state-of-the-art atmospheric chemistry and transport models. The remarkably high OH concentrations were also supported by results of a simple budget analysis, based on the flux-to-lifetime relationship of isoprene within the CBL. Furthermore, VOC fluxes determined with the airborne MLG approach were only in reasonable agreement with those of the tower-based REA and SLG approaches after correction for chemical decay by OH radicals, applying a best estimate OH concentration of 5.5×106 molecules cm−3. The SCM model calculations support relatively high OH concentration estimates after specifically being constrained by the mixing ratios of chemical constituents observed during the campaign. The relevance of the VOC fluxes for the local carbon budget of the tropical rainforest site during the measurements campaign was assessed by comparison with the concurrent CO2 fluxes, estimated by three different methods (eddy correlation, Lagrangian dispersion, and mass budget approach). Depending on the CO2 flux estimate, 1–6% or more of the carbon gained by net ecosystem productivity appeared to be re-emitted through VOC emissions.

scholarly journals Isoprene and monoterpene fluxes from Central Amazonian rainforest inferred from tower-based and airborne measurements, and implications on the atmospheric chemistry and the local carbon budget

2007 ◽  
Vol 7 (1) ◽  
pp. 641-708 ◽  
Author(s):  
U. Kuhn ◽  
M. O. Andreae ◽  
C. Ammann ◽  
A. C. Araújo ◽  
E. Brancaleoni ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Reasonable Agreement ◽  
Carbon Budget ◽  
Eddy Correlation ◽  
Oh Radicals ◽  
Model Calculations ◽  
Airborne Measurements ◽  
Mixing Ratios ◽  
Budget Analysis ◽  
Vertical Gradients

Abstract. We estimated the isoprene and monoterpene source strengths of a pristine tropical forest north of Manaus in the central Amazon Basin using three different micrometeorological flux measurement approaches. During the early dry season campaign of the Cooperative LBA Airborne Regional Experiment (LBA-CLAIRE-2001), a tower-based surface layer gradient (SLG) technique was applied simultaneously with a relaxed eddy accumulation (REA) system. Airborne measurements of vertical profiles within and above the convective boundary layer (CBL) were used to estimate fluxes on a regional scale by application of the mixed layer gradient (MLG) technique. The mean daytime fluxes of organic carbon measured by REA were 2.1 mg C m−2 h−1 for isoprene, 0.20 mg C m−2 h−1 for α-pinene, and 0.39 mg C m−2 h−1 for the sum of monoterpenes. These values are in reasonable agreement with fluxes determined with the SLG approach, which exhibited a higher scatter, as expected for the complex terrain investigated. The observed VOC fluxes are in good agreement with simulations using a single-column chemistry and climate model (SCM). In contrast, the model-derived mixing ratios of VOCs were by far higher than observed, indicating that chemical processes may not be adequately represented in the model. The observed vertical gradients of isoprene and its primary degradation products methyl vinyl ketone (MVK) and methacrolein (MACR) suggest that the oxidation capacity in the tropical CBL is much higher than previously assumed. A simple chemical kinetics model was used to infer OH radical concentrations from the vertical gradients of (MVK+MACR)/isoprene. The estimated range of OH concentrations during the daytime was 3–8×106 molecules cm−3, i.e., an order of magnitude higher than is estimated for the tropical CBL by current state-of-the-art atmospheric chemistry and transport models. The remarkably high OH concentrations were also supported by results of a simple budget analysis, based on the flux-to-lifetime relationship of isoprene within the CBL. Furthermore, VOC fluxes determined with the airborne MLG approach were only in reasonable agreement with those of the tower-based REA and SLG approaches after correction for chemical decay by OH radicals, applying a best estimate OH concentration of 5.5×106 molecules cm−3. The SCM model calculations support relatively high OH concentration estimates after specifically being constrained by the mixing ratios of chemical constituents observed during the campaign. The relevance of the VOC fluxes for the local carbon budget of the tropical rainforest site during the measurements campaign was assessed by comparison with the concurrent CO2 fluxes, estimated by three different methods (eddy correlation, Lagrangian dispersion, and mass budget approach). Depending on the CO2 flux estimate, 1–6% or more of the carbon gained by net ecosystem productivity appeared to be re-emitted through VOC emissions.

scholarly journals Exploration of the atmospheric chemistry of nitrous acid in a coastal city of southeastern China: results from measurements across four seasons

2022 ◽  
Vol 22 (1) ◽  
pp. 371-393
Author(s):  
Baoye Hu ◽  
Jun Duan ◽  
Youwei Hong ◽  
Lingling Xu ◽  
Mengren Li ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Simulation Models ◽  
Oh Radicals ◽  
Vehicle Exhaust ◽  
Southeastern China ◽  
Coastal City ◽  
Budget Analysis ◽  
Four Seasons ◽  
Conversion Frequency

Abstract. Because nitrous acid (HONO) photolysis is a key source of hydroxyl (OH) radicals, identifying the atmospheric sources of HONO is essential to enhance the understanding of atmospheric chemistry processes and improve the accuracy of simulation models. We performed seasonal field observations of HONO in a coastal city of southeastern China, along with measurements of trace gases, aerosol compositions, photolysis rate constants (J), and meteorological parameters. The results showed that the average observed concentration of HONO was 0.54 ± 0.47 ppb. Vehicle exhaust emissions contributed an average of 1.45 % to HONO, higher than the values found in most other studies, suggesting an influence from diesel vehicle emissions. The mean conversion frequency of NO2 to HONO in the nighttime was the highest in summer due to water droplets evaporating under high-temperature conditions. Based on a budget analysis, the rate of emission from unknown sources (Runknown) was highest around midday, with values of 4.51 ppb h−1 in summer, 3.51 ppb h−1 in spring, 3.28 ppb h−1 in autumn, and 2.08 ppb h−1 in winter. Unknown sources made up the largest proportion of all sources in summer (81.25 %), autumn (73.99 %), spring (70.87 %), and winter (59.28 %). The photolysis of particulate nitrate was probably a source in spring and summer while the conversion from NO2 to HONO on BC enhanced by light was perhaps a source in autumn and winter. The variation of HONO at night can be exactly simulated based on the HONO / NOx ratio, while the J(NO3-_R) × pNO3- should be considered for daytime simulations in summer and autumn, or 1/4× (J(NO3-_R) × pNO3-) in spring and winter. Compared with O3 photolysis, HONO photolysis has long been an important source of OH except for summer afternoons. Observation of HONO across four seasons with various auxiliary parameters improves the comprehension of HONO chemistry in southeastern coastal China.

scholarly journals Diurnal variations of reactive chlorine and nitrogen oxides observed by MIPAS-B inside the January 2010 Arctic vortex

2012 ◽  
Vol 12 (14) ◽  
pp. 6581-6592 ◽  
Author(s):  
G. Wetzel ◽  
H. Oelhaf ◽  
O. Kirner ◽  
F. Friedl-Vallon ◽  
R. Ruhnke ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Climate Model ◽  
Michelson Interferometer ◽  
Emission Spectra ◽  
The Arctic ◽  
Polar Stratospheric Clouds ◽  
Model Calculations ◽  
Mixing Ratios ◽  
Reservoir Species ◽  
Stratospheric Clouds

Abstract. The winter 2009/2010 was characterized by a strong Arctic vortex with extremely cold mid-winter temperatures in the lower stratosphere associated with an intense activation of reactive chlorine compounds (ClOx) from reservoir species. Stratospheric limb emission spectra were recorded during a flight of the balloon version of the Michelson Interferometer for Passive Atmospheric Sounding (MIPAS-B) from Kiruna (Sweden) on 24 January 2010 inside the Arctic vortex. Several fast limb sequences of spectra (in time steps of about 10 min) were measured from nighttime photochemical equilibrium to local noon allowing the retrieval of chlorine- and nitrogen-containing species which change rapidly their concentration around the terminator between night and day. Mixing ratios of species like ClO, NO2, and N2O5 show significant changes around sunrise, which are temporally delayed due to polar stratospheric clouds reducing the direct radiative flux from the sun. ClO variations were derived for the first time from MIPAS-B spectra. Daytime ClO values of up to 1.6 ppbv are visible in a broad chlorine activated layer below 26 km correlated with low values (below 0.1 ppbv) of the chlorine reservoir species ClONO2. Observations are compared and discussed with calculations performed with the 3-dimensional Chemistry Climate Model EMAC (ECHAM5/MESSy Atmospheric Chemistry). Mixing ratios of the species ClO, NO2, and N2O5 are well reproduced by the model during night and noon. However, the onset of ClO production and NO2 loss around the terminator in the model is not consistent with the measurements. The MIPAS-B observations along with Tropospheric Ultraviolet-Visible (TUV) radiation model calculations suggest that polar stratospheric clouds lead to a delayed start followed by a faster increase of the photodissoziation of ClOOCl and NO2 near the morning terminator since stratospheric clouds alter the direct and the diffuse flux of solar radiation. These effects are not considered in the EMAC model simulations which assume a cloudless atmosphere.

scholarly journals OH regeneration from methacrolein oxidation investigated in the atmosphere simulation chamber SAPHIR

2014 ◽  
Vol 14 (15) ◽  
pp. 7895-7908 ◽  
Author(s):  
H. Fuchs ◽  
I.-H. Acir ◽  
B. Bohn ◽  
T. Brauers ◽  
H.-P. Dorn ◽  
...  
Keyword(s):  
Reaction Pathway ◽  
Chemical Mechanism ◽  
Isomerization Reaction ◽  
Initial Reaction ◽  
Oh Radicals ◽  
Peroxy Radicals ◽  
Atmospheric Conditions ◽  
Model Calculations ◽  
Mixing Ratios ◽  
Simulation Chamber

Abstract. Hydroxyl radicals (OH) are the most important reagent for the oxidation of trace gases in the atmosphere. OH concentrations measured during recent field campaigns in isoprene-rich environments were unexpectedly large. A number of studies showed that unimolecular reactions of organic peroxy radicals (RO2) formed in the initial reaction step of isoprene with OH play an important role for the OH budget in the atmosphere at low mixing ratios of nitrogen monoxide (NO) of less than 100 pptv. It has also been suggested that similar reactions potentially play an important role for RO2 from other compounds. Here, we investigate the oxidation of methacrolein (MACR), one major oxidation product of isoprene, by OH in experiments in the simulation chamber SAPHIR under controlled atmospheric conditions. The experiments show that measured OH concentrations are approximately 50% larger than calculated by the Master Chemical Mechanism (MCM) for conditions of the experiments (NO mixing ratio of 90 pptv). The analysis of the OH budget reveals an OH source that is not accounted for in MCM, which is correlated with the production rate of RO2 radicals from MACR. In order to balance the measured OH destruction rate, 0.77 OH radicals (1σ error: ± 0.31) need to be additionally reformed from each reaction of OH with MACR. The strong correlation of the missing OH source with the production of RO2 radicals is consistent with the concept of OH formation from unimolecular isomerization and decomposition reactions of RO2. The comparison of observations with model calculations gives a lower limit of 0.03 s−1 for the reaction rate constant if the OH source is attributed to an isomerization reaction of MACR-1-OH-2-OO and MACR-2-OH-2-OO formed in the MACR + OH reaction as suggested in the literature (Crounse et al., 2012). This fast isomerization reaction would be a competitor to the reaction of this RO2 species with a minimum of 150 pptv NO. The isomerization reaction would be the dominant reaction pathway for this specific RO2 radical in forested regions, where NO mixing ratios are typically much smaller.

scholarly journals HO<sub>x</sub> measurements in the summertime upper troposphere over Europe: a comparison of observations to a box model and a 3-D model

2012 ◽  
Vol 12 (11) ◽  
pp. 30619-30660 ◽  
Author(s):  
E. Regelin ◽  
H. Harder ◽  
M. Martinez ◽  
D. Kubistin ◽  
C. Tatum Ernest ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Circulation Model ◽  
Box Model ◽  
Measurement Unit ◽  
Data Set ◽  
Upper Troposphere ◽  
Sources And Sinks ◽  
Airborne Measurements ◽  
Mixing Ratios

Abstract. In-situ airborne measurements of OH and HO2 with the HORUS (HydrOxyl Radical measurement Unit based on fluorescence Spectroscopy) instrument were performed in the summertime upper troposphere across Europe during the HOOVER 2 (HOx OVer EuRope) campaign in July 2007. Complementary measurements of trace gas species and photolysis frequencies were conducted to obtain a broad data set, which has been used to quantify the significant HOx sources and sinks. In this study we compare the in-situ measurement of OH and HO2 with simulated mixing ratios from the constrained box model CAABA/MECCA (Chemistry As A Box Model Application/Module Efficiently Calculating the Chemistry of the Atmosphere), and the global circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry Model). The constrained box model reproduces the observed OH and HO2 mixing ratios with better agreement (obs/mod median 98% OH, 96% HO2) than the global model (median 76% OH, 59% HO2). The observations and the computed HOx sources and sinks are used to identify deviations between the models and their impacts on the calculated HOx budget.

scholarly journals HOx measurements in the summertime upper troposphere over Europe: a comparison of observations to a box model and a 3-D model

2013 ◽  
Vol 13 (21) ◽  
pp. 10703-10720 ◽  
Author(s):  
E. Regelin ◽  
H. Harder ◽  
M. Martinez ◽  
D. Kubistin ◽  
C. Tatum Ernest ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Circulation Model ◽  
Box Model ◽  
Measurement Unit ◽  
Data Set ◽  
Upper Troposphere ◽  
Sources And Sinks ◽  
Airborne Measurements ◽  
Mixing Ratios

Abstract. In situ airborne measurements of OH and HO2 with the HORUS (HydrOxyl Radical measurement Unit based on fluorescence Spectroscopy) instrument were performed in the summertime upper troposphere across Europe during the HOOVER 2 (HOx OVer EuRope) campaign in July 2007. Complementary measurements of trace gas species and photolysis frequencies were conducted to obtain a broad data set, which has been used to quantify the significant HOx sources and sinks. In this study we compare the in situ measurement of OH and HO2 with simulated mixing ratios from the constrained box model CAABA/MECCA (Chemistry As A Box Model Application/Module Efficiently Calculating the Chemistry of the Atmosphere), and the global circulation model EMAC (ECHAM5/MESSy Atmospheric Chemistry Model). The constrained box model reproduces the observed OH and HO2 mixing ratios with better agreement (obs/mod median 98% OH, 96% HO2) than the global model (median 76% OH, 59% HO2). The observations and the computed HOx sources and sinks are used to identify deviations between the models and their impacts on the calculated HOx budget.

scholarly journals OH regeneration from methacrolein oxidation investigated in the atmosphere simulation chamber SAPHIR

2014 ◽  
Vol 14 (4) ◽  
pp. 5197-5231 ◽  
Author(s):  
H. Fuchs ◽  
I.-H. Acir ◽  
B. Bohn ◽  
T. Brauers ◽  
H.-P. Dorn ◽  
...  
Keyword(s):  
Nitrogen Monoxide ◽  
Reaction Rate Constant ◽  
Isomerization Reaction ◽  
Initial Reaction ◽  
Oh Radicals ◽  
Peroxy Radicals ◽  
Atmospheric Conditions ◽  
Model Calculations ◽  
Mixing Ratios ◽  
Simulation Chamber

Abstract. Hydroxyl radicals (OH) are the most important reagent for the oxidation of trace gases in the atmosphere. OH concentrations measured during recent field campaigns in isoprene rich environments were unexpectedly large. A number of studies showed that unimolecular reactions of organic peroxy radicals (RO2) formed in the initial reaction step of isoprene with OH play an important role for the OH budget in the atmosphere at low mixing ratios of nitrogen monoxide (NO) of less than 100 pptv. It has also been suggested that similar reactions potentially play an important role for RO2 from other compounds. Here, we investigate the oxidation of methacrolein (MACR), one major oxidation product of isoprene, by OH in experiments in the simulation chamber SAPHIR under controlled atmospheric conditions. The experiments show that measured OH concentrations are approximately 50% larger than calculated by current chemical models for conditions of the experiments (NO mixing ratio of 90 pptv). The analysis of the OH budget reveals a so far unaccounted OH source, which is correlated with the production rate of RO2 radicals from MACR. In order to balance the measured OH destruction rate, (0.77±0.3) OH radicals need to be additionally reformed from each OH that has reacted with MACR. The strong correlation of the missing OH source with the production of RO2 radicals is consistent with the concept of OH formation from unimolecular isomerization and decomposition reactions of RO2. The comparison of observations with model calculations gives a lower limit of 0.03 s−1 for the reaction rate constant, if the OH source is attributed to an isomerization reaction of one RO2 species formed in the MACR+OH reaction as suggested in literature. This fast isomerization reaction would be competitive to the reaction of this RO2 species with minimum 150 pptv NO.

scholarly journals New approach to evaluate satellite derived XCO<sub>2</sub> over oceans by integrating ship and aircraft observations

2020 ◽  
Author(s):  
Astrid Müller ◽  
Hiroshi Tanimoto ◽  
Takafumi Sugita ◽  
Toshinobu Machida ◽  
Shin-ichiro Nakaoka ◽  
...  
Keyword(s):  
Carbon Cycle ◽  
Atmospheric Chemistry ◽  
Transport Model ◽  
Satellite Observations ◽  
Reference Dataset ◽  
Model Calculations ◽  
New Approach ◽  
Mixing Ratios ◽  
In Situ Data

Abstract. Satellite observations provide spatially-resolved global estimates of column-averaged mixing ratios of CO2 (XCO2) over the Earth's surface. The accuracy of these datasets can be validated against reliable standards in some areas, but other areas remain inaccessible. To date, limited reference data over oceans hinders successful uncertainty quantification or bias correction efforts, and precludes reliable conclusions about changes in the carbon cycle in some regions. Here, we propose a new approach to analyze and evaluate seasonal, interannual and latitudinal variations of XCO2 over oceans by integrating cargo-ship (SOOP, Ship Of Opportunity) and commercial aircraft (CONTRAIL, Comprehensive Observation Network for Trace gases by Airliner) observations with the aid of state-of-the art atmospheric chemistry-transport model calculations. The consistency of the in situ based column-averaged CO2 dataset (in situ XCO2) with satellite estimates was analyzed over the Western Pacific between 2014 and 2017, and its utility as reference dataset evaluated. Our results demonstrate that the new dataset accurately captures seasonal and interannual variations of CO2. Retrievals of XCO2 over the ocean from GOSAT (Greenhouse gases observing satellite: NIES v02.75, National Institute for Environmental Studies; ACOS v7.3, Atmospheric CO2 Observation from Space) and OCO-2 (Orbiting Carbon Observatory, v9r) observations show a negative bias of about 1 parts per million (ppm) in northern midlatitudes, which was attributed to measurement uncertainties of the satellite observations. The NIES retrieval had higher consistency with in situ XCO2 at midlatitudes as compared to the other retrievals. At low latitudes, it shows many fewer valid data and high scatter, such that ACOS and OCO-2 appear to provide a better representation of the carbon cycle. At different times, the seasonal cycles of all three retrievals show positive phase shifts of one month relative to the in situ data. The study indicates that even if the retrievals complement each other, remaining uncertainties limit the accurate interpretation of spatiotemporal changes in CO2 fluxes. A continuous long-term XCO2 dataset with wide latitudinal coverage based on the new approach has a great potential as a robust reference dataset for XCO2 and can help to better understand changes in the carbon cycle in response to climate change using satellite observations.

scholarly journals Exploration of the atmospheric chemistry of nitrous acid in a coastal city of southeastern China: Results from measurements across four seasons

2021 ◽  
Author(s):  
Baoye Hu ◽  
Jun Duan ◽  
Youwei Hong ◽  
Lingling Xu ◽  
Mengren Li ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Nitrous Acid ◽  
Simulation Models ◽  
Oh Radicals ◽  
Vehicle Exhaust ◽  
Southeastern China ◽  
Coastal City ◽  
Budget Analysis ◽  
Four Seasons ◽  
Conversion Frequency

Abstract. Because nitrous acid (HONO) photolysis is a key source of hydroxyl (OH) radicals, identifying the atmospheric sources of HONO is essential to enhance the understanding of atmospheric chemistry processes and improve the accuracy of simulation models. We performed seasonal field observations of HONO in a coastal city of southeastern China, along with measurements of trace gases, aerosol compositions, photolysis rate constants (J), and meteorological parameters. The results showed that the average observed concentration of HONO was 0.54 ± 0.47 ppb. Vehicle exhaust emissions contributed an average of 1.64 % to HONO, higher than the values found in most other studies, suggesting an influence from diesel vehicle emissions. The mean conversion frequency of NO2 to HONO in the nighttime was the highest in summer due to water droplets was evaporated under the condition of high temperatures. Based on a budget analysis, the rate of emission from unknown sources (Runknown) was highest around midday, with values of 4.35 ppb · h−1 in summer, 3.53 ppb · h−1 in spring, 3.13 ppb · h−1 in autumn, and 2.05 in winter. Unknown sources made up the largest proportion of all sources in summer (78.55 %), autumn (71.51 %), spring (69.67 %), and winter (55.63 %). The photolysis of particulate nitrate was probably a source in spring and summer while the conversion from NO2 to HONO on BC enhanced by light was perhaps a source in autumn and winter. The variation of HONO at night can be exactly simulated based on the HONO/NOx ratio, while the J(NO3−_R) × pNO3− should be considered for daytime simulations in summer and autumn, or 1/4 × (J(NO3−_R) × pNO3−) in spring and winter. Compared with O3 photolysis, HONO photolysis has long been an important source of OH except for summer afternoon. Observation on HONO across four seasons with various auxiliary parameters improves the comprehension of HONO chemistry in southeastern coastal China.

Airborne Measurements of Trace Organic Species in the Upper Troposphere Over Europe: the Impact of Deep Convection

2006 ◽  
Vol 3 (4) ◽  
pp. 244 ◽  
Author(s):  
Aurélie Colomb ◽  
Jonathan Williams ◽  
John Crowley ◽  
Valérie Gros ◽  
Rolf Hofmann ◽  
...  
Keyword(s):  
Atmospheric Chemistry ◽  
Deep Convection ◽  
Trace Gases ◽  
Upper Troposphere ◽  
Airborne Measurements ◽  
Organic Species ◽  
Mixing Ratios ◽  
Benzene Toluene ◽  
The Impact ◽  
Organic Trace

Environmental Context. In the upper troposphere, sources of HOx such as acetone, peroxides, and aldehydes can play an important role in governing the production and destruction of ozone. Convection (over both land and sea) carries gases that can contribute to increased levels of HOx to the upper troposphere. The chemical impact of convection on the continental upper troposphere over Europe is studied by sampling the upper troposphere. Mass spectrometry techniques are used to analyze the collected samples. Such a study should aid in understanding the impact meteorological events have on atmospheric chemistry. Abstract. The volume mixing ratios of several organic trace gases and ozone (O3) were measured in the upper troposphere over Europe during the UTOPIHAN-ACT aircraft campaign in July 2003. The organic trace gases included alkanes, isoprene, aromatics, iodomethane, and trichloroethylene, oxygenates such as acetone, methanol, formaldehyde, carbon monoxide, and longer-lived tracer species such as chlorofluorocarbons and halochloroflurocarbons. The aim of the UTOPIHAN-ACT project was to study the chemical impact of deep convection on the continental upper troposphere. A Lear Jet aircraft, based in Germany, was flown at heights between 6 and 13 km in the region 59°N–42°N to 7°W–13°E during July 2003. Overall, the convectively influenced measurements presented here show a weaker variability lifetime dependence of trace gases than similar measurements collected over the Mediterranean region under more stable high-pressure conditions. Several cases of convective outflow are identified by the elevated mixing ratios of organic species relative to quiescent background conditions, with both biogenic and anthropogenic influences detectable in the upper troposphere. Enhancement at higher altitudes, notably of species with relatively short chemical lifetimes such as benzene, toluene, and even isoprene indicates deep convection over short timescales during summertime. The impact of deep convection on the local upper tropospheric formaldehyde and HOx budgets is assessed.

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