for Numerical Weather Prediction in Europe
Many parts of the world have recently experienced high impact
meteorological events which have disrupted national services, damaged or destroyed
infrastructure and resources, and have resulted in the loss of human life.
In 2001 over 1000 people died in Algeria as a result of
mudslides and flooding caused by torrential downpours. Over 100mm of rain fell
in a few hours over central Algiers, the equivalent to what
is normally received in a month.
- The flooding in Prague (Czech Republic, 2002) led to 200,000 people being evacuated
from their homes, with 90 people killed across central and eastern Europe.
- In Arles (France, 2003) 30,000 people were evacuated as a result
of severe flooding, seven people loosing their lives.
- The summer of 2003
was the warmest on record in many parts of Western Europe. An estimated 20,000 people including at least
10,000 in France, and some 2,000 each in Italy and the UK died as a result of physiological stress brought
on by an extreme heat wave during the hottest part of the summer.
- 140 million people
were affected by flooding when over 60% of Bangladesh was flooded in 2004. 600 people died with over
1 million acres of crops destroyed.
Changes in the future climate as a consequence of anthropogenic
emission of greenhouse gases are predicted to lead to a warmer world. Not only
will there be significant impacts to our environment due to sustained higher
temperatures, but extreme heat waves such as that of 2003 may become more
commonplace, and a more vigorous hydrological cycle is likely to result in an
increased number of extreme, high impact phenomena such as droughts, fluvial
flooding, and severe storm events. The impact on society could be great with
the disruption of energy production and communication networks weakening
national security; destruction of crops could lead to famine and warfare;
interruption to water supplies could lead to deterioration in human health;
overall the loss of human life will increase.
Today’s Numerical Weather Prediction (NWP) systems are capable of
predicting many of these events but not with the required accuracy or at
sufficient lead-time to enable all possible mitigating action to be taken to
protect life and property; nor are the civil decision making tools in place to
reduce the impact of these events.
There is an expectation of further significant improvements in NWP
systems over the next decade. Higher resolution models will provide more detail
for small scale severe weather events. Continued improvements to the observing
network including new satellite instruments, more data from aircraft, improved
radar systems and the use of targeted observations will provide better initial
conditions which are critical for short and medium range forecasting. However, because of the inevitable uncertainty
in initial conditions and also the uncertainty in forecast models, the further
deployment and use of ensembles is essential for the early warning and
quantification of the risk of severe weather.
There is a growing consensus that the needs of the global
community can best be met through the provision of a global ensemble forecasting
system, together with re-locatable regional limited area ensemble systems,
supported by targeted observations.
These needs have been recognised through the establishment of
THORPEX, a ten-year long international research programme to accelerate
improvements in the accuracy of 1 to 14-day weather forecasts for the benefit
of society and the economy, as a part of the WMO World Weather Research
Programme. Such a system would allow governments and trans-national
organisations such as the UN to take intelligent decisions based on the
minimisation of societal exposure to weather-related risk, generate optimal mitigation
strategies, and maximise the efficiency of the humanitarian effort.
Today, Europe enjoys a diverse NWP capability covering a very broad spectrum.
Different model formulations, temporal and spatial ranges and resolutions are
deployed to meet a range of customer requirements and funding bases. Mechanisms
for research, development and operational implementation also vary. To name but
a few, there are modelling communities such as ALADIN, COSMO and HIRLAM. There are Centres with a particular WMO or customer
focus, such as the Regional Specialised Meteorological Centres at Toulouse, Offenbach, Rome, Exeter and Reading covering geographical specialisation, atmospheric transport and global
medium-range products, and the London World Area Forecast Centre providing
global aviation products.
European scientists in many of the groups and centres have been at
the forefront of this international effort in increasing the quality of
short-range regional predictions and of global predictions on the short-,
medium- and longer ranges. As a result, there are Centres in Europe which have developed scientific
reputations that are second to none and whose forecast accuracies are
recognised as the best in the world.
The continuing success of the European effort in NWP is based on
our ability to increase European capability whilst at the same time maintaining
a diversity of modelling approaches. This has been achieved through a long
established balance between the differing national requirements, financial
contributions and scientific effort. The multi-model seasonal ensemble run at
ECMWF is an example of where diversity has led to increased capability to the
benefit of Europe as a whole. The friendly competition and
collaboration between Met Services and ECMWF has resulted in the proving of
ideas in systems that use fundamentally different numerical techniques, thereby
demonstrating their scientific validity. These differing approaches have not
hindered collaboration, but have stimulated discussion and collaboration
through EUMETSAT SAFs, EU funded projects and EUMETNET SRNWP.
There is now the opportunity to build on this diversity,
maximising the value of European meteorology with the capability at hand. Concerted
cooperation within Europe would provide society with the information
it will need to ensure the conservation of human life. This
will allow Europe to actively respond to the findings of
THORPEX, enabling our expertise to benefit the rest of the world.
The vision is based on the following realities and presumptions:
- There is the
continued development of a limited number of independently formulated state
of the art NWP systems with that number potentially reducing. National
Meteorological and Hydrological Services (NMHSs) will still function to
provide service delivery to its designated geographical area of
responsibility, including the issuing of severe weather warnings to its
government and population
- The resolution of
existing global and regional models will increase over the next twenty
years to the extent that global models will supplant regional models and
regional models will supplant country scale models for all but the most
detailed customer requirements.
- Uncertainties in
model formulation and the initial state of the atmosphere result in deterministic
forecasts that are not always correct. On both global and regional scales, there
is a need to quantify the uncertainty to give a better chance of
identifying a high impact, low probability event. Ensemble Prediction Systems
(EPS) have been established for this purpose at a number of Centres. A Multi-model
EPS could provide significant additional benefits over and above a single
EPS. They have been shown to capture uncertainties associated with model
formulation and the significant increased size of the super ensemble is
more likely to capture low-frequency high-impact events. However,
multi-model ensembles are unlikely to represent the full spectrum of model
uncertainty and a more generalised framework for the formulation of
weather prediction may be required, whereby specific realisations of
sub-grid processes are represented by stochastic-dynamic parametrisations.
Extensive numerical experimentation, probably in an operational context,
will be required to assess the merits of stochastic-dynamic parametrisations
within the context of multi-model and other related representations of
- There is a growing
European capability through joint activities that is focused on delivering
tools to enhance the mitigation of meteorological related disasters (i.e.
- This implies the
need for a much greater
collaborative effort between NHMS’s both globally and within Europe who have the independent capability to
maintain, develop and run either global or regional high resolution models
supported by EPS and to support the interchange of lateral boundary
conditions between the different systems.
A Co-ordinated Europe
In summary the vision is of a cooperative of Met Services who
combine their various skills and capabilities to ensure all within Europe are provided with the best environmental
forecast possible, allowing impact scenarios to provide optimum planning
information for our nations.
This vision relies upon supporting technology to enable multiple,
geographically separated centres to generate a timely and reliant ensemble
product. In the near future virtual computing across Europe may allow the easy exchange of data and
products in a timely and efficient manner. The issues of GRID technology is
being investigated through the EU funded projects, which are illustrating the
limitations of the technology available to us today. However, data is already
being reliably exchanged through this technology.
We would expect prototype systems at today’s resolutions to be in
place on the 5 year timeframe. The full vision could be realised within 10
years and be the basis of European and Global Meteorology through until 2025.
diagram of vision
Global NWP and Multi-Model
Ensemble Prediction System
Europe has several organisations which have a
global NWP capability. Such organisations would coordinate their independently
formulated NWP systems to generate high resolution global NWP and supporting
EPS, for the period 0-14 days. These organisations would be linked together to
exchange data over a distributed GRID network to contribute to a single MM-EPS
Target resolutions for the initial implementation of 20km for
global deterministic NWP and 50km for global EPS is achievable with projected
computer systems during the next few years. In time atmosphere-ocean coupled
models would be implemented.
Limited Area NWP Multi-model
Ensemble Prediction System
The global solution is mirrored on a regional scale. There are
several groupings and countries within Europe that have great skill in Limited Area
Modelling and have significant computing power and advanced supporting
infrastructures. Through coordinating this effort these centres would take
products from the global centres and run regional NWP supported by regional
EPS. Each organisation would be linked through a grid network to allow MM-EPS
regional products to be generated. Target resolutions of 4km for regional NWP
and 10km for regional EPS are suggested and again this is achievable with
projected computer systems during the next few years. Taking the products from
the regional and global NWP and MM-EPS, the NMHS’s would then issue forecasts
and warnings to their own geographical area of responsibility.
Centres of Excellence
Within Europe there are already
several centres with a particular WMO
responsibility or customer focus, such as the Regional Specialised
Meteorological Centres at Toulouse, Offenbach, Rome, Exeter and Reading. Taking this
approach one step further in light of this coordinated approach, Centres of
Excellence would be established having a specific role and responsibility. The management
of the GRID network; the development of post processing techniques; the
standardization of NWP model output; development of visualization systems; development
of ensemble tools; the coordination of warnings to Europe’s NMHSs for example
on the risk of forest fires, fluvial flooding, avalanches, severe storms, high
seas; issuing of air quality forecasts, to mention a few would need to be managed
To achieve the greatest level of skill in forecasting in both the
medium range and for complex severe impact systems a competent and flexible
observation network is necessary. In
data sparse areas targeted observations will be required. The coordination of
this targeting would need to be done globally, although the European component
(perhaps covering the Atlantic region) would be managed through a Centre of
With such an interdependent system the robustness of the
forecasting ensemble system will need to be such that if one or more of the
forecasting organisations were to fail, the integrity of the ensemble product
should not adversely suffer. Redundancy within the system would therefore be
required. Multiple Centres provides such redundancy. Conversely having multiple
sources for the products would increase global and European forecasting
resilience, mitigate meteorological risk whilst optimally utilising the global
community knowledge base.
Country scale NWP
As a consequence of the above, NMHS would have a vastly superior
quality of products at their disposal to aid in the prevention of loss of life
and property. Resources within each organisation could be freed to allow the
development of downstream products for the user community. It is likely that
here will still be a need for high resolution (1-2km) non-hydrostatic NWP which
will help predict small scale high impact phenomena. These models could be run at the NMHS or at a
regional centre on behalf of an NMHS.
Europe supporting the
Europe can, as a whole, realise its full
potential through adopting a networked approach to NWP, ensuring
diversification, whilst making the most of the technical capability at hand.
Accepting the need to collaborate more closely will also enable Europe to contribute both global and regional
ensembles in support of the THORPEX programme.
The development of re-locatable, high resolution ensemble models
could be used to forecast high impact meteorological events not only within Europe, but wherever there was a need. Some of
the severest natural disasters occur in the poorest, least developed parts of
the world. Having re-locatable high resolution models together with targeted
observations would ensure that all of the globe would benefit from the technological
capability available within the most developed nations.
Together we’re stronger
The vision reflects the new possibilities created by advancements
in science and technology. It is the duty of the National Meteorological
Services to utilize these advancements.
The vision is consistent with the role of the National
Meteorological Services and thus, if implemented, will not change this role.
The National Meteorological Services have been established because national
governments have a duty to provide their population with forecasts of high
impact weather. Implementation of the vision will, through international
cooperation in NWP, improve the quality of such forecasts.
Implementation of the vision will require substantial international
cooperation. It is difficult to imagine that such cooperation could take place
between competing firms in the private meteorological sector, but it can be
realized between governmental National Meteorological Services.
For years, we have had a deterministic approach to weather
forecasting, yet is has been clear to everyone that the forecasts should more
suitably have been given in the form of probabilities. In fact this has led to
a presentational problem with the general public which will be solved through
the realisation of the vision.
Looking at the situation in Europe today, we are already on our way towards
this vision, although perhaps without being fully conscious of this. The NWP
situation in Europe, with its balance between cooperation
and diversity, is an excellent basis for delivering a forecasting system that
will benefit the whole of Europe, and the global community.