Verlag des Forschungszentrums Jülich
JUEL-3822
The experimental investigations of anthropogenic plumes in the planetary boundary layer (TACIA) and the remote free troposphere (ACSOE) are interpreted by heuristic model calculations. The model set-up, with modules for transport and chemistry, allows for a separation of these processes in the analysis. The transport module in combination with the CO observations is shown to be a useful tool for the analysis of emissions and transport. Convective transport into the free troposphere is identified by combination of the transport module with satellite data.
The interpretation of observations distant from the source regions, with respect to the in-fluence of anthropogenic VOC and NOx emissions on the ozone formation in a plume, is made by an indirect inverse modelling approach. The method involves extensive sensitivity studies regarding various initial VOC and NOx concentrations, in an EKMA framework. Despite the large degree of abstraction, the results of EKMA plot calculations can be com-pared to the measurements with the help of CO as emission tracer and enable the depend-ency of the observed O3 on anthropogenic VOC and NOx emissions to be analysed.
A central point of this study is the use of statistical test methods for the analysis of the sig-nificance of deviations between model results and measurements. Sensitivity studies, re-garding the dependence of model results on the variability of input parameters, are ana-lysed with respect to confidence regions of the observations.
With these means, the following general conclusions regarding ozone formation in conti-nental plumes transported into source free maritime areas are obtained:
The O3 formation within the PBL depends on a multitude of parameters. It is shown for the example of the TACIA flight A581, that the natural variability and uncertainties of these parameters are still too high for an unambiguous interpretation of observed O3 formation in a continental plume with respect to anthropogenic NOx and VOC emis-sions. This complicates the task of estimating the influence of export of pollution-derived ozone and its precursors on the remote troposphere.
Schmitgen, Sandra
Use of airborne CO measurements for Lagrangian analysis of ozone formation and transport in continental plumes
182 S., 2000
The anthropogenic ozone budget is investigated in remote regions with respect to the influ-ence of emissions of VOC and NOx at source regions, and with regard to the relative roles of ozone formation in the polluted boundary layer (PBL) and in the free troposphere (FT). The investigation makes use of airborne measurements aboard the United Kingdom Mete-orological Office (UKMO) C-130 Hercules aircraft obtained during the European project TACIA (Testing Atmospheric Chemistry in Anticyclones) and the UK project ACSOE (Atmospheric Chemistry Studies in Oceanic Environment). High resolution measurements of CO as a quasi-inert tracer of anthropogenic emissions were made and interpreted.
The layers of enhanced CO and O3 in the FT, observed during ACSOE flight A575, can only partly be explained by in-situ production of ozone in the FT. Higher O3 pro-duction efficiencies on a per-molecule basis of NOx in the FT compared to the PBL are found to be compensated by the reduced NOx availability in the free troposphere, related to CO. PBL-produced O3 is found not only to be important close to source regions, but also for long range transport within the FT in connection with cloud venting, where it contributes to the tropospheric budget of ozone.
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