Geoscience Reference
In-Depth Information
Chapter 4
Geographical Information for the Initialization
of Numerical Weather Forecast Models and
Climate Modeling
4.1. Introduction
Numerical models have been used operationally in weather prediction centers
since the 1970s; since then, they have been subject to large improvements, either in
terms of performances due to improved computer capabilities, increasingly precise
descriptions of physical and chemical processes involved, improved horizontal and
vertical resolutions and use of increasingly relevant observations [PAI 02].
Climate models which are derived from numerical weather prediction models
generally include a much more detailed description of atmospheric composition.
They have also improved dramatically, both for demonstrating climate predictability
at monthly, seasonal or inter-annual timescales [PAL 04], and for the study of
climate scenarios, i.e. the response of the climate system to different hypotheses on
the evolution of the global socio-economical context. These different scenarios of
our future climate have been the subject of assessment reports produced by the
Intergovernmental Panel on Climate Change (IPCC). More information can be
found in the 2007 fourth IPCC Assessment Report [IPC 07].
4.2. Brief description of the climate system
The climate system consists of five major components which interact at different
time and space scales (see Figure 4.1):
- the atmosphere,
- the hydrosphere (liquid water at and underneath the Earth's surface: ocean,
rivers, lakes, ground water),
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