Environmental Engineering Reference
In-Depth Information
4.12 Model Evaluation of Regional Chemistry
Transport Models
Peter Builtjes
1
and Robert Vautard
2
1
TNO Enviroment and Geosciences, Utrecht, The Netherlands
2
LSCE/IPSL Laboratoire CEA/CNRS/UVSQ, Gif sur Yvette Cedex, France
Abstract
In Europe, over the last decade several model intercomparison and
model evaluation studies have been carried out. Using several models in a model
evaluation study has the clear advantage that the model results are not just
compared to observations, but that the models are also tested against each other.
Model evaluation studies have been performed first for ozone, but more recently
also for PM, and the components of PM. In general, the studies have been focused
on the overall model performance, without focussing on specific processes. The
studies show that most CTM's are capable of simulation ozone concentrations, but
that there are still major problems with modelling PM.
Keywords
Modelling, evaluation
1. Introduction
The first step in a model evaluation study should be to define the purpose of the
model, to be able to determine whether the model is “fit-for-purpose”. In case the
model is used to study in detail a specific process like for example in cloud
scavenging or dry deposition, then the model evaluation should be process oriented,
and will be of a scientific character. The observations used come in that case often
from dedicated field campaigns. More operational, and policy oriented model
applications ask for an overall model evaluation, and for observations often use is
made from existing networks.
Gradually, elements of a model evaluation protocol have been made and tested.
As stated, the first step should be to define the purpose of the model. The next step
should be to identify the processes required in the model. For example, modelling
the CH4-concentration over an extended period does not require that a module for
aerosol chemistry is included in the model. Further, the horizontal and vertical
resolution, and the time scale should be defined.
Concerning the input data like meteorology and emissions, it should be decided
whether these data are considered as “correct”, or whether they should be evalu-
ated separately. In most European model evaluation studies the emissions are
