Keywords:
stratosphere
;
ozone
;
chemistry
;
climate models
Description / Table of Contents:
Three-dimensional climate models with a fully interactive representation of stratospheric ozone chemistry
— otherwise known as stratosphere-resolving chemistry-climate models (CCMs) — are key tools for the
attribution and prediction of stratospheric ozone changes arising from the combined effects of changes in the
amounts of greenhouse gases (GHG) and ozone-depleting substances (ODS). These models can also be used to
infer potential effects of stratospheric changes on the climate of the troposphere. In order to know how much
confi dence can be placed in the results from the CCMs, both individually and collectively, it is necessary to assess
their performance by comparison with observations and known physical constraints.
The Stratospheric Processes And their Role in Climate (SPARC) core project of the World Climate Research
Programme (WCRP) initiated the CCM Validation (CCMVal) activity in 2003 to coordinate exactly such an
evaluation. The CCMVal concept (see Chapter 1) takes as a starting point the premise that model performance is
most accurately assessed by examining the representation of key processes, rather than just the model’s ability
to reproduce long-term ozone trends, as the latter can be more easily tuned and can include compensating errors.
Thus a premium is placed on high-quality observations that can be used to assess the representation of key
processes in the models. This Report does not provide a detailed assessment of the quality of the observational
databases; the compilation and assessment of data sets suitable for model evaluation is the focus of a future
SPARC activity, which has been motivated by this Report.
The fi rst round of CCMVal (CCMVal-1) evaluated only a limited set of key processes in the CCMs, focusing
mainly on dynamics and transport. This Report, which describes the second round of CCMVal (CCMVal-2),
represents a more complete effort by CCMVal to assess CCM performance. As with CCMVal-1, it also includes
an assessment of the extent to which CCMs are able to reproduce past observations in the stratosphere, and the
future evolution of stratospheric ozone and climate under one particular scenario. A key aspect of the model
evaluation within this Report is the application of observationally-based performance metrics to quantify the
ability of models to reproduce key processes for stratospheric ozone and its impact on climate. The Report is
targeted at a variety of users, including: (1) international climate science assessments, including the WMO/
UNEP Ozone Assessments and the IPCC Assessment Reports; (2) the CCM groups themselves; (3) users of
CCM simulations; (4) measurement and process scientists who wish to help improve CCM evaluation; (5)
space agencies and other bodies involved in the Global Climate Observing System.
The Report was prepared by dozens of scientists and underwent several revisions and extensive peer review,
culminating in a Final Review Meeting in Toledo, Spain on November 9-11, 2009.
Pages:
Online-Ressource (XXXVIII, 426 Seiten)
URL:
http://www.sparc-climate.org/publications/sparc-reports/sparc-report-no5/
Language:
English
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