per square. The output is consequently a coarse-scale average over
urban, rural, and remote location; thus inaccuracies can arise when
comparing the model output with field measurements. Additionally,
when the number of parcels is limited interpolation errors can
arise in circumstances where grid squares do not contain any
Lagrangian cells. STOCHEM has previously been used for global
investigations, including those modelling the transport of chemical
species (Collins et al., 1999; Johnson et al., 2002; Sanderson et al.,
2003). In this study, STOCHEM is used to reveal the global burden
of peroxy radicals, their localised concentrations at specific measurement
stations, and the distribution of RO2.H2O complexes. The
simulationwas conducted with meteorology from 1998 for a period
of 24 months with the first 12 allowing the model to spin up.
Analysis is performed on the subsequent 12 months of data.