Tropospheric ozone during the MINOS campaign: model simulations and analysis
Geert-Jan Roelofs, Bert Scheeren and Tasos Kentarchos
Institute for Marine and Atmospheric Research Utrecht (IMAU),
Utrecht University, the Netherlands
The MINOS measurement campaign in August 2001 was based on Crete (Greece)
and had as purpose to measure the chemical composition of the troposphere
in the Mediterranean region during summer, to analyse the influences of
chemical and dynamical processes, and investigate regional climate effects.
With the aid of tropospheric chemistry-climate model simulations we
analysed the concentrations of ozone and ozone precursors observed during
measurement flights from MINOS. The model is based on ECHAM4, which is
coupled to a tropospheric chemistry module that accounts for emissions of
ozone precursors, higher hydrocarbon chemistry, dry and wet deposition, and
stratosphere-troposphere exchange of chemical species. The model
realistically represents the measured ozone vertical gradients, generally
displaying highest ozone concentrations in the middle troposphere between 5
and 8 km altitude. Model analysis indicates a significant contribution from
relatively ozone-rich stratospheric air in this layer, that lasted
throughout most of the MINOS period. The atmospheric dynamics over a large
part of south-east Europe are dominated by the western side of a strong
upper-tropospheric anti-cyclone centered over the Tibetan Plateau,which
cause steep vertical potential temperature gradients and therefore lead to
efficient transport of a relatively thin layer of upper tropospheric/lower
stratospheric air from high latitudes southward to the eastern
Mediterranean region. Smaller scale features in ozone concentrations,
possibly related to convective transports, remain unresolved by the model.
In this study we will analyse the influences of atmospheric dynamical and
chemical processes associated with the air mass source regions on regional
ozone distributions, and discuss the anthropogenic contribution.