Natural Hazards and Earth System Sciences. Nonlinear Processes in Geophysics. The Cryosphere. Weather and Climate Dynamics. Advances in Geosciences. Encyclopedia of Geosciences. Journal topic AMT. Author Title Abstract Full text. User ID.
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Prof. Dr. Ralf Koppmann
Volume 7, issue 10 Atmos. This work is distributed under the Creative Commons Attribution 3. Show only first author papers Show all papers. Short summary.
Experimental evidences that the regeneration efficiency of the OH radical is maintained globally at values higher than 0. In addition, current available models were tested and suggestions on how to improve their ability to reproduce the measured radical and oxygenated volatile organic compound concentrations are provided.
We use in situ observations of H 2 O 2 to study the interplay between photochemistry, transport and deposition processes. The data were obtained during five ground-based field campaigns across Europe. A budget calculation indicates that the photochemical production rate was much larger than photochemical loss and that dry deposition is the dominant loss process. To reproduce the change in H 2 O 2 mixing ratios after sunrise, a variable contribution of entrainment from the residual layer is required.
Sascha R. Within this study we demonstrate reliable measurement of hydroperoxy HO 2 radicals via chemical ionisation mass spectrometry. HO 2 is detected as an ion cluster with bromide ions, which allows a selective detection. This direct and sensitive measurement provides reliable data of HO 2 radical concentrations in the atmosphere as demonstrated in the first application in simulation chamber experiments.
John N. Crowley, Nicolas Pouvesle, Gavin J. Simultaneous observations of PAA, PAN and H 2 O 2 are used to provide insight into processes influencing the HO x chemistry of the boreal forest, including two biomass-burning-impacted periods. A significant contribution from photolytic HO x sources was included in a box model analysis to align model predictions with measurements.
The model predicts high levels of organic peroxy radicals, also at night-time. OH concentrations are nearly 2-fold larger than those observed in foreign cities during wintertime.
The high OH and large OH reactivities indicate photochemical processes can be effective even during wintertime. A box model largely underestimated HO 2 and RO 2 concentrations during pollution episodes correlated with high NO x , indicating a deficit current chemistry in the high NO x regime. MBO is a volatile organic compound mainly emitted by ponderosa and lodgepole pines which are very abundant in forests in the central-west USA.
OH and HO 2 control the transformation of air pollutants and O 3 formation.
Their implication for air quality over the climatically sensitive Mediterranean region was studied during a field campaign in Cyprus. Box model simulations of OH and HO 2 agreed with measurements except at high terpene concentrations when model RO 2 due to terpenes caused large HO 2 loss. Autoxidation schemes for RO 2 improved the agreement. The photooxidation of methyl vinyl ketone MVK, one of the most important products of isoprene that is emitted by plants, was investigated in the atmospheric simulation chamber SAPHIR for conditions found in forested areas.
The comparison of measured trace gas time series with model calculations shows a gap in the understanding of radical chemistry in the MVK oxidation scheme. The possibility of unimolecular isomerization reactions were investigated by means of quantum-chemical calculations. Defeng Zhao, Sebastian H. Cryer, Charlotte A. Brumby, Lisa K. Whalley, Daniel Stone, Paul W. Seakins, Dwayne E. Thames, William H. Hydroxyl radical reactivity k OH is closely related to processes that lead to the formation of oxidised, secondary pollutants such as ozone and aerosol. Chemical conditions were chosen either to be representative of the atmosphere or to test potential limitations of instruments.
Overall, the results show that instruments are capable of measuring k OH. The aim of the study was to examine aged air masses being transported from the European continent towards Cyprus.
POPCORN: A Field Study of Photochemistry in North-Eastern ...
Longer-lived oxygenated volatile organic compounds OVOCs such as methanol were mainly impacted by long-distance transport and showed higher values in air masses from eastern Europe than in a flow regime from the west. The ambient concentration of stabilised Criegee intermediates SCIs was estimated for two environments using field data. The low concentrations predicted indicate that SCIs are unlikely to have a large impact on atmospheric chemistry.
There are many studies which show discrepancies between modeled and measured nitrous acid HONO, precursor of OH radical in the troposphere but with no satisfactory explanation. Budget analysis of trace gas measurements indicates a common source of NO and HONO, which is not related to anthropogenic activity and is most likely derived from biologic activity in soils and subsequent emission. Oswald, M. Ermel, K. Hens, A. Novelli, H. Ouwersloot, P. Paasonen, T. Keronen, J. Hosaynali Beygi, H. Fischer, B. Bohn, D. Kubistin, H. Harder, M. Martinez, J.
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Hoffmann, I. Trebs, and M. Nitrous acid HONO is a key species in atmospheric photochemistry since the photolysis leads to the important hydroxyl radical OH. We present a detailed analysis of sources and sinks for HONO in the atmosphere for a field measurement campaign in the boreal forest in Finland and wonder if there is really a source term missing. Novelli, M. Auld, R. Axinte, B.