4
E. Raschke
(and accuracy!) with numerical models. Such global numerical models are now used for the
simulation of the present and prediction of future states of weather over 3 to 10 days, or the
weather statistics during the next season, the ocean circulations or even the development of the
climate in general during the next decades (e.g.: Cubasch et al., 1995; Kumar and Hoerling,
1995). Research is underway to use them also for the reconstruction of the climate during past
historical periods considering different external forcing scenarios.
More demands than ever before are now occuring to this field of science from the open public, due to the issue of increasing concentrations of the greenhouse gases carbon dioxide and
methane, and also of others. The world's population increases further and will in future need
more food, more water and also more space to live and to dump and recycle its waste and other
disposals.
But also many immediate applications benefit already at present from an improved forecasting
of atmospheric and surface properties and also ocean currents, depending on the space and time
scale. In fact, one estimates an annual global saving of the world's economy by about 30-40
Bill. US-$, due to the present days use of informations to be derived from weather forecasts at
different scales.
The nation's decisionmakers need reliable and believable information on future developments
over the next decades not only of their own economies and the future developments in their
countries but also on the climate and its impact on the use of the earth's surface and related
resources. This information enables them to reach national and international agreements on
possibly drastic and expensive measures to keep our climate system in an acceptable state,
which does not cause too strong social unrest, provide such a state can be defined and reliably
predicted.
The World Meteorological Organization (WMO) and other bodies have, therefore, invited many
scientists to advice them in these matters within the framework of the Intergovernmental Panel
on Climate and Climate Changes (IPCC, 1996, to appear). Their reports reflect the state of
art of the present understanding of the earth's climate. In it also some conclusions are made
on the development of the climate during the upcoming 50 years.
As one possible and quite straightforward way to meet these demands one has chosen to built up
systems of numerical simulation models, which are capable to consider all relevant processes in
the climate system, i.e. within the atmosphere and coupled to it the oceans, continents and the
cryosphere. This strategy arose from the practices of numerical weather forecast. It is the basis
of the World Climate Research Programme (WCRP). The performance of such models needs
detailed and careful validation of results which have been calculated for the present climate. It
must be based on reliable observations.
But many ground-based observational systems degrade in quantity and quality and need increasingly be supplemented by space borne and other automatic observations. Furthermore, we
still do not know the regional and temporal distribution of most climate variables well enough
over areas where almost no "ground-truth" is yet available, such as over all oceans and other
continental areas, and the many global atmospheric models compute still quite different results
for the same input. Very few direct measurements are available over the oceans.
The many careful intercomparisons of model results within the Atmospheric Model Intercomparison Project (AMIP, see Gates, 1992) and also of various model components, such as the
routines for radiation having been intercompared during the International Comparison of Radiation Codes in Climate Models (ICRCCM; Ellingson and Fouquart, 1993) or the PILPS-project
concentrating on land-surface processes over vegetated areas (Henderson-Sellers, 1995) have
demonstrated the need for a better understanding of the various processes involved in energy
and water transfers.
E. Raschke
(and accuracy!) with numerical models. Such global numerical models are now used for the
simulation of the present and prediction of future states of weather over 3 to 10 days, or the
weather statistics during the next season, the ocean circulations or even the development of the
climate in general during the next decades (e.g.: Cubasch et al., 1995; Kumar and Hoerling,
1995). Research is underway to use them also for the reconstruction of the climate during past
historical periods considering different external forcing scenarios.
More demands than ever before are now occuring to this field of science from the open public, due to the issue of increasing concentrations of the greenhouse gases carbon dioxide and
methane, and also of others. The world's population increases further and will in future need
more food, more water and also more space to live and to dump and recycle its waste and other
disposals.
But also many immediate applications benefit already at present from an improved forecasting
of atmospheric and surface properties and also ocean currents, depending on the space and time
scale. In fact, one estimates an annual global saving of the world's economy by about 30-40
Bill. US-$, due to the present days use of informations to be derived from weather forecasts at
different scales.
The nation's decisionmakers need reliable and believable information on future developments
over the next decades not only of their own economies and the future developments in their
countries but also on the climate and its impact on the use of the earth's surface and related
resources. This information enables them to reach national and international agreements on
possibly drastic and expensive measures to keep our climate system in an acceptable state,
which does not cause too strong social unrest, provide such a state can be defined and reliably
predicted.
The World Meteorological Organization (WMO) and other bodies have, therefore, invited many
scientists to advice them in these matters within the framework of the Intergovernmental Panel
on Climate and Climate Changes (IPCC, 1996, to appear). Their reports reflect the state of
art of the present understanding of the earth's climate. In it also some conclusions are made
on the development of the climate during the upcoming 50 years.
As one possible and quite straightforward way to meet these demands one has chosen to built up
systems of numerical simulation models, which are capable to consider all relevant processes in
the climate system, i.e. within the atmosphere and coupled to it the oceans, continents and the
cryosphere. This strategy arose from the practices of numerical weather forecast. It is the basis
of the World Climate Research Programme (WCRP). The performance of such models needs
detailed and careful validation of results which have been calculated for the present climate. It
must be based on reliable observations.
But many ground-based observational systems degrade in quantity and quality and need increasingly be supplemented by space borne and other automatic observations. Furthermore, we
still do not know the regional and temporal distribution of most climate variables well enough
over areas where almost no "ground-truth" is yet available, such as over all oceans and other
continental areas, and the many global atmospheric models compute still quite different results
for the same input. Very few direct measurements are available over the oceans.
The many careful intercomparisons of model results within the Atmospheric Model Intercomparison Project (AMIP, see Gates, 1992) and also of various model components, such as the
routines for radiation having been intercompared during the International Comparison of Radiation Codes in Climate Models (ICRCCM; Ellingson and Fouquart, 1993) or the PILPS-project
concentrating on land-surface processes over vegetated areas (Henderson-Sellers, 1995) have
demonstrated the need for a better understanding of the various processes involved in energy
and water transfers.