HR: 16:00h
AN: A14D-01 INVITED    [Abstracts]
TI: Emission Rate and Chemical State Assessments by Nested 4D-Variational Chemistry Data Assimilation
AU: * Elbern, H
EM: he@eurad.uni-koeln.de
AF: Rhenish Institute for Environmental Research at the University of Cologne, Aachener Strasse 209, Cologne, NRW D-50935, Germany
AU: Strunk, A
EM: as@eurad.uni-koeln.de
AF: Rhenish Institute for Environmental Research at the University of Cologne, Aachener Strasse 209, Cologne, NRW D-50935, Germany
AB: The presentation demonstrates the potential and limits of an advanced inversion method to estimate pollutant precursor sources from observations, both in situ and satellite tropospheric columns. Ozone, sulphur dioxide, and partly nitrogen oxides observations are taken to infer source strength estimates. As methodology, the four--dimensional variational data assimilation technique has been generalised and employed to include emission rate optimisation, in addition to chemical state estimates as usual objective of data assimilation. To this end, the optimisation space of the variational assimilation system has been complemented by emission rate correction factors of 19 emitted species at each emitting grid point, involving the University of Cologne mesoscale EURAD model. For validation, predictive skills were assessed for several ozone episodes, comparing forecast performances of pure initial value optimisation, pure emission rate optimisation, and joint emission rate/initial value optimisation. Validation procedures rest on both measurements withheld from data assimilation and prediction skill evaluation of forecasts after the inversion procedures. Results show that excellent improvements can be claimed for sulphur dioxide forecasts, after emission rate optimisation. Significant improvements can be claimed for ozone forecasts after initial value and joint emission rate/initial value optimisation of precursor constituents. The additional benefits applying joint emission rate/initial value optimisation are moderate, and very useful in typical cases, where upwind emission rate optimisation is essential. The poor representativity of NO_x observations enforced augmentation of the 4D-var system by multi level nesting techniques. The improvements of the analysis result with increasing horizontal resolution, starting from a 54 km mother grid down to 6 km finest grid.
UR: http://www.atmos-chem-phys.net/7/3749/2007/acp-7-3749-2007.html
DE: 0322 Constituent sources and sinks
DE: 0345 Pollution: urban and regional (0305, 0478, 4251)
DE: 0365 Troposphere: composition and chemistry
DE: 0368 Troposphere: constituent transport and chemistry
SC: Atmospheric Sciences [A]
MN: 2007 Fall Meeting