Ozone Production in the Atmosphere Simulation Chamber SAPHIR
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Beschreibung
Tropospheric ozone in high concentrations is harmful for mankind and the
environment as a whole. As it is a greenhouse gas, its rising due to anthropogenic
emissions of the precursor species contributes to global warming. By
being the precursor specie for all oxidizing agents in the atmosphere, e.g. the
highly reactive OH radical, and being an oxidizing agent itself, ozone is very
important in atmospheric chemistry.
Due to this importance, a sound understanding of the chemical ozone production
processes is needed. The necessary precursors for the photochemical
production are the mainly anthropogenic nitrogen oxides NOx and the both
anthropogenic and biogenic volatile organic compounds. In principle, the processes
are fairly understood. In details huge uncertainties still exist. These
have to be examined further to allow for well-founded predictions of short and
long term ozone concentrations, e.g. to early warn the population off injurious
values to come or for the use in climate change modelling.
In the atmosphere simulation chamber SAPHIR chemical processes of the
troposphere can be examined nearly without physical caused changes, like
transport, mixing, or unknown sources and sinks of trace constituents. Ambient
conditions concerning trace gas concentrations, temperature, pressure and
lighting conditions characterize the SAPHIR experiments. To understand the
complex processes influencing trace gas concentrations in nature, field experiments
are obligatory. For the interpretation of measured field data model
calculations are needed to distinguish between chemical and physical influences.
The test of these models is only feasible under the physically controlled
conditions inside the SAPHIR chamber.
In this thesis, three different approaches, which strongly vary concerning
their needed (measured) input and the computational effort, for the prediction
of the photochemical ozone production were tested against SAPHIR chamber
experiments. First of all model runs on the basis of the Master Chemical
Mechanism, which compiles the state of the art knowledge in atmospheric
chemistry in one mechanism, were tested at ambient trace gas concentrations
for the first time. These model runs only need few measured input but a high
computational effort. The newly developed First Degradation Step approach in
contrast needs a lot of measured input, which then is combined by fundamental
arithmetic to calculate the ozone production. The third, also new approach
tested is an even simpler method, which estimates the ozone production by a
simple combination of measured OH concentrations and OH lifetimes.
Autor*in
Cornelia A Richter