On the budget of hydroxyl radicals at Schauinsland during the Schauinsland Ozone Precursor Experiment (SLOPE96)

Volz‐Thomas, A.; Kolahgar, Bita

doi:10.1029/1999jd901046

Cited by 30 publications

(22 citation statements)

References 57 publications

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“…Mean noon OH concentrations are 1.2 ϫ 10 7 molecules cm Ϫ3 at Verzago and 9 ϫ 10 6 molecules cm Ϫ3 at Bresso. The OH-radical levels in relation to the NO x concentrations at these two sites are within the range of results from measurements or estimates in other experiments [Daum et al, 2000;Volz-Thomas and Kolahgar, 2000].…”

Section: Radical Concentrationssupporting

confidence: 81%

NO_x versus VOC limitation of O₃ production in the Po valley: Local and integrated view based on observations

et al. 2002

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[1] We characterize the local O 3 production at an urban and a rural site in the northern part of the Po valley (Italy) during the Pianura Padana Produzione di Ozono experiment (PIPAPO). A steady state calculation based on observations is performed to determine the local O 3 production rate, P(O 3 ), and its sensitivity to precursor concentrations. The urban site exhibited a strongly VOC sensitive O 3 production rate, while both VOC and NO x sensitive conditions were observed at the rural site. In addition to the local steady state analysis, we performed one-dimensional Lagrangian model calculations that simulate conditions in the Po valley. These calculations show that the P(O 3 ) at the surface tends to be more VOC sensitive than the average in the mixed layer. The Lagrangian calculations are also used to determine the response of O 3 concentration to an emissions change. We compare emission control information with information on sensitivities from the local analysis. It is concluded that a local analysis of P(O 3 ) within the mixing layer offers useful qualitative information but tends to overestimate VOC sensitivity as judged by a comparison with an emissions-based Lagrangian model.

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Section: Radical Concentrationssupporting

confidence: 81%

NO_x versus VOC limitation of O₃ production in the Po valley: Local and integrated view based on observations

et al. 2002

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“…, 1997; George et al , 1999; Frost et al , 1999; Carslaw et al , 1999]. Volz‐Thomas and Kolahgar [2000] also reported a case where measured OH was higher than modeled.…”

Section: Model‐measurement Comparisonsmentioning

confidence: 89%

Loss of isoprene and sources of nighttime OH radicals at a rural site in the United States: Results from photochemical models

et al. 2002

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[1] A one-dimensional Lagrangian model for atmospheric transport and photochemistry has been developed and used to interpret measurements made at Pellston, Michigan, during the summer of 1998. The model represents a moving vertical column of air with vertical resolution of 25 m near the ground. Calculations have been performed for a series of trajectories, with representation of emissions, vertical mixing, and photochemistry for a 3-day period ending with the arrival of the air column at Pellston. Results have been used to identify causes of the observed decrease in isoprene at night, to investigate causes of high nighttime OH. Significant OH can be generated at night by terpenes if it is assumed that some fast-reacting monoterpenes are emitted at rates comparable to inventory emissions for terpenes. However, this nighttime OH is confined to a shallow surface layer (0 -25 m) and has little impact on nighttime chemistry. The observed decrease in isoprene at night can be reproduced in models with low OH, and is attributed primarily to vertical dilution. There is also evidence that transport from Lake Michigan contributes to low nighttime isoprene at Pellston. Model results compare well with measured isoprene, NO x , and with isoprene vertical profiles. Significant model-measurement discrepancies are found for OH, HO 2 , methylvinylketone, and formaldehyde.

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“…The aim of this experiment was to perform a Lagrangian study of polluted air masses, making interceptions several times using 4 different research aircraft during their transport from North America to Europe. Lagrangian experiments have been conducted previously, for example, in the stratosphere [ Rex et al , 1998] using balloons, or close to emission regions [ Daum et al , 2000; Volz‐Thomas and Kolahgar , 2000]. This is the first time that a Lagrangian experiment has been conducted in the free troposphere on intercontinental scales.…”

Section: Introductionmentioning

confidence: 99%

Processes influencing ozone levels in Alaskan forest fire plumes during long‐range transport over the North Atlantic

et al. 2007

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[1] A case of long-range transport of a biomass burning plume from Alaska to Europe is analyzed using a Lagrangian approach. This plume was sampled several times in the free troposphere over North America, the North Atlantic and Europe by three different aircraft during the IGAC Lagrangian 2K4 experiment which was part of the ICARTT/ ITOP measurement intensive in summer 2004. Measurements in the plume showed enhanced values of CO, VOCs and NO y , mainly in form of PAN. Observed O 3 levels increased by 17 ppbv over 5 days. A photochemical trajectory model, CiTTyCAT, was used to examine processes responsible for the chemical evolution of the plume. The model was initialized with upwind data and compared with downwind measurements. The influence of high aerosol loading on photolysis rates in the plume was investigated using in situ aerosol measurements in the plume and lidar retrievals of optical depth as input into a photolysis code (Fast-J), run in the model. Significant impacts on photochemistry are found with a decrease of 18% in O 3 production and 24% in O 3 destruction over 5 days when including aerosols. The plume is found to be chemically active with large O 3 increases attributed primarily to PAN decomposition during descent of the plume toward Europe. The predicted O 3 changes are very dependent on temperature changes during transport and also on water vapor levels in the lower troposphere which can lead to O 3 destruction. Simulation of mixing/dilution was necessary to reproduce observed pollutant levels in the plume. Mixing was simulated using background concentrations from measurements in air masses in close proximity to the plume, and mixing timescales (averaging 6.25 days) were derived from CO changes. Observed and simulated O 3 /CO correlations in the plume were also compared in order to evaluate the photochemistry in the model. Observed slopes change from negative to positive over 5 days. This change, which can be attributed largely to photochemistry, is well reproduced by multiple model runs even if slope values are slightly underestimated suggesting a small underestimation in modeled photochemical O 3 production. The possible impact of this biomass burning plume on O 3 levels in the European boundary layer was also examined by running the model for a further 5 days and comparing with data collected at surface sites, such as Jungfraujoch, which showed small O 3 increases and elevated CO levels. The model predicts significant changes in O 3 over the entire 10 day period due to photochemistry but the signal is largely lost because of the effects of dilution. However, measurements in several other BB plumes over Europe show that O 3 impact of Alaskan fires can be potentially significant over Europe.

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On the budget of hydroxyl radicals at Schauinsland during the Schauinsland Ozone Precursor Experiment (SLOPE96)

Cited by 30 publications

References 57 publications

NO_x versus VOC limitation of O₃ production in the Po valley: Local and integrated view based on observations

NO_x versus VOC limitation of O₃ production in the Po valley: Local and integrated view based on observations

Loss of isoprene and sources of nighttime OH radicals at a rural site in the United States: Results from photochemical models

Processes influencing ozone levels in Alaskan forest fire plumes during long‐range transport over the North Atlantic

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On the budget of hydroxyl radicals at Schauinsland during the Schauinsland Ozone Precursor Experiment (SLOPE96)

Cited by 30 publications

References 57 publications

NOx versus VOC limitation of O3 production in the Po valley: Local and integrated view based on observations

NOx versus VOC limitation of O3 production in the Po valley: Local and integrated view based on observations

Loss of isoprene and sources of nighttime OH radicals at a rural site in the United States: Results from photochemical models

Processes influencing ozone levels in Alaskan forest fire plumes during long‐range transport over the North Atlantic

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NO_x versus VOC limitation of O₃ production in the Po valley: Local and integrated view based on observations

NO_x versus VOC limitation of O₃ production in the Po valley: Local and integrated view based on observations