28 August 2006Steinhausen meeting Hamburg On the integration of weather and climate prediction Lennart Bengtsson

28 August 2006 Steinhausen meetingHamburg

On the integration of weather and climate prediction

Lennart Bengtsson


On the integration of weather and climate prediction

• What has been achieved in weather and climate modeling?

• What are probably now the most pressing issues?

• What is needed to achieve this?

• A strategy for climate prediction in Europe


What has been achieved in weather modeling?

• Useful global prediction of synoptic scale weather for more than a week ahead

• Successful introduction of ensemble prediction

• Modest achievements in seasonal prediction of weather anomalies


Improvements in NWP from Miyakoda (1972) to 2002. Courtesy ECMWF

How long to get to D+10 in winter?

2006 at day 9


St. Petersburg ensemble prediction 10.1 2006

17th onward ca -30 C


What has been achieved in climate modeling?

• Realistic simulation of the general circulation of the atmosphere including many extreme features

• Major progress in simulating key aspects of the ocean circulation

• Progress in incorporating the interactions with the biosphere

• Demonstrating with relatively high probability that climate variations during the 20th century have been dominated by natural climate processes

• Demonstrating ( with high probability) that the climate trend of the 20th century cannot be explained without anthropogenic forcing

• Simulations of the climate of the 21st century with increasingly realistic models


ECHAM5simulated

ERA40determined

from analyses.

Köppen climate zones


CoupledModelT63L31

Present climate

Future climate


Observes and simulated QBONote the marked changes in wind direction at 10-20 hPa every 26-28

month


20th Century (20C3M)

11/20 models have decadal signal

PIcntrl (Control Runs)10/20 models have decadal signal

IPCC AR4 Arctic Temperature Anomalies by AOGCMs

Courtesy, J Overland


50-year trends>0.23 corresponds to 95% significance

T

PZ 850

Sea

ice


Ten coldest European wintersmodel and “observations” ( Luterbacher, 2005)

Model Obs

Model global anomaly

Model height

500 hPa


Pre-industrial temperatures in Europe (DJF)Model results

( smaller numbers in right column are observed values prior to 1950 covering ca 200 years

Mean T STD T Min Max

De Bilt +4.3 +2.0 1.4 1.8 -1.0 -3.1 +7.6 +5.3

Hamburg +1.4 1.8 -5.0 +5.6

Hohenpeissenb. -1.6 -1.4 1.8 1.9 -6.9 -6.1 +2.2 +2,8

Paris +3.8 + 3.3 1.4 1.6 -0.8 -1.6 +6.8 +6.6

Oxford +5.1(L) 1.2(L) +0.1 +8.0

Moscow -10.6 2.6 -19.7 -2.0

Uppsala -2.5 -4.0 1.7 2.3 -8.0 -9.9 +1.8 +1.4

St. Petersburg -8.5 -7.2 2.2 2.6 -15.7 -14.6 -1.5 -1.1

Warsaw -3.3 -2.8 2.2 2.3 -11.7 -9.2 +2.3 +1.4

Vienna -2.3 -0.5 1.9 1.8 - 8.5 -5.8 +2.1 +3.3


T213 Cyclones (>1x103 sec-1), 1960-1990.

Simulation of hurricane trajectory during 30 years

ECHAM5 model at T213 resolution

Storms with 850 mb max. vorticity stronger than 10-3 s-1

Selected storm trajectory


Intensity v Speed (T213)


T213 Example Cyclone

Intensity and Speed MSLP

T63 Vertical Structure


T213 Regional Speed Distribution.


Effect of resolutionComparing ECHAM5 T213 with T63

Max. Speed (m/sec)

)

#/year


Number of observed, ERA-40 analyzed and simulated by ECHAM5 (T159) hurricanes having a maximum wind

speed higher than 33ms-1


What are probably now the most pressing issues?

• To better clarify what is predictable and not predictable

• To better clarify the climate feedback processes

• To determine the regional climate change and its separation from natural climate variability

• To estimate risks of extreme events on different time scales


Climate precdictability

• This will require models resolving high amplitude features

• This will require ensemble prediction to separate signal from noise

• This will require more advanced modeling and significantly increased computer resources


Climate feedback processes

• The handling of clouds in models is the single most important issue

• This is likely to require higher resolutions as clouds are associated with weather systems at different scales

• This will require detailed validation and experimentation using best possible observed data. It will best be used to use the models in a forecasting mode


Predicting risks of extreme events

• Significant harm to society is related to high frequency synoptic events ( hurricanes, extra-tropical storms) and to longer lasting anomalies such as heat waves and droughts

• Longer term risks include flooding in coastal areas related to sea level rise

• Global type risks (probably longer term), melting of Greenland ice, West Antarctica, major changes in ocean circulation


A strategy for climate prediction in Europe

• There is a need for regular climate prediction to support environmental policies

• Europe has in climate and environmental policy more or less common interests and objectives

• In order to keep and enhance credibility in modeling this could best be achieved by a European agency with long term commitments of an operational nature

• Required resources in man power and computers can hardly be found on a national level in the longer term


A strategy for climate prediction in Europe

• A joint European climate modeling and prediction initiative could be set up as an integrated part of ECMWF but with a research program organized in a different way

• Most of the research could best be done within national research units as now but with the difference that the work is done within a common framework

• A changed convention for ECMWF is presently being approved by the national governments and is expected to come into force in 2007

• The new ECMWF convention will make it possible to set up a climate prediction program


END

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28 August 2006Steinhausen meeting Hamburg On the integration of weather and climate prediction Lennart Bengtsson