M. Lautenschlager (M&D/MPIM) 19.03.2002 1

Changing Weather PatternsWeather: Yesterday - Today - Tomorrow

Michael LautenschlagerModelle und Daten /

Max-Planck-Institut für Meteorologie,Hamburg

AON - Seminar:"Catastrophe Modelling, Techniques and Applications"

09.04.02 in Amsterdam

M. Lautenschlager (M&D/MPIM) 19.03.2002 2

Weather: Yesterday - Today - Tomorrow

Content:1) Introduction / Overview

Low pressure systems and stormsDefinition of weather and climate

2) Climate Development on Different Time ScalesIce Ages (100,000 years)Little Ice Age (500 years)Industrialisation (100 years)

3) Climate Modelling PrinciplesPhenomena within climate modelsLimits of resolution

4) IPCC Third Assessment ReportDefinition of climate modelling experimentsGlobal temperature increaseGlobal sea level riseRegional temperature responseRegional precipitation response

5) OutlookNorth Atlantic deep water formationStorm frequency over North-western Europe

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Hurricane Georges (Sept. 1998 in the Caribbean)

Strongest hurricane since 20 yearsWind speed: 200 km/hPeaks: 250 km/hTrajectory: Florida was

not hidden

For comparison gale (Orkan): Wind strength 12 bft with Wind speed > 120 km/h

1946 WMO increases the Beaufort-Scale up to 17 bft

Tropical phenomenon:Water temperature > 27°C

M. Lautenschlager (M&D/MPIM) 19.03.2002 4

Northern Hemisphere Low Pressure System

Core pressure: Surface low 990-1000 hPaGale low 950 -970 hPaHigh 1025-1030 hPa

Pressure gradient determinesthe wind strength:Storm 4 hPa / 100 km

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Definition of Weather and Climate

• Weather"Weather is concerned with detailed instantaneous states of the atmosphere and with the day-to-day evolution of individual synoptic systems. The atmosphere is characterised by relatively rapid random fluctuations in time and space so that weather, identified as the complete state of the atmosphere at a given instant, is continuously changing." (Peixoto and Oort, 1993)

• ClimateThe climate, on the other hand, can be considered as the "averaged weather", completed with some measures of variability of its elements and with information on the occurrence of extreme events. Thus we may note that the same variables that are relevant in the weather and in other branches of meteorology are also those that are important in the characterisation of climate." (Peixoto and Oort, 1993)

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Weather: Yesterday - Today - Tomorrow

Content:1) Introduction / Overview

2) Climate Development on Different Time ScalesIce Ages (100,000 years)Little Ice Age (500 years)Industrialisation (100 years)

3) Climate Modelling Principles

4) IPCC Third Assessment Report

5) Outlook

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Global temperaturereduction of approx. 5°C

Sea level reductionof approx. 180 m

(Comp. expectedglobal warming)

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Last Interglacial

Temperature increase in Central-Greenland:

+ 20°C in 5000 years

Younger Dryas(rapid climatechange)

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IPCC TAR (2001)

Industrialisation

Future development?

M. Lautenschlager (M&D/MPIM) 19.03.2002 10

Weather: Yesterday - Today - Tomorrow

Content:1) Introduction / Overview

2) Climate Development on Different Time Scales

3) Climate Modelling PrinciplesPhenomena within climate modelsLimits of resolution

4) IPCC Third Assessment Report

5) Outlook

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Phenomena and Processes in Climate Models

Noreiks (MPIM), 2001

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Radiation Transfer and Greenhouse Effect

Greenhouse effect:Intensification by Means of CO

2

increase

Noreiks (MPIM), 2002

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Limits of model resolution

ECHAM4(T42)Grid resolution: 2.8°Time step: 40 min

ECHAM4(T106)Grid resolution: 1.1°Time step: 20 min

Standard resolution for IPCC TAR

The climate model calculates:"averaged weather" and variability

Noreiks (MPIM), 2001

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See Slides from Jena

DKRZ Computing Environment

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DKRZ Computing Environment

February 2002Compute server: 64 CPUs NEC-SX6, 0.5 TB memory, 200 GFlops sustained performance (appr. 40 * C916)Data server: 720 TB tape capacity, 30 TB disk capacity,240 MB/sec LAN band width

August 2002Compute and data server increase by a factor of 2

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Weather: Yesterday - Today - Tomorrow

Content:1) Introduction / Overview

2) Climate Development on Different Time Scales

3) Climate Modelling Principles

4) IPCC Third Assessment ReportDefinition of climate modelling experimentsGlobal temperature increaseGlobal sea level riseRegional temperature responseRegional precipitation response

5) Outlook

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1 Climate change in IPCC usage refers to any change in climate over time, whether due to natural variability or as a result of human activity. This usage differsfrom that in the Framework Convention on Climate Change, where climate change refers to a change of climate that is attributed directly or indirectly tohuman activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparable time periods.2 In total 122 Co-ordinating Lead Authors and Lead Authors, 515 Contributing Authors, 21 Review Editors and 337 Expert Reviewers.3 Delegations of 99 IPCC member countries participated in the Eighth Session of Working Group I in Shanghai on 17 to 20 January 2001.

IPCC Third Assessment Report (TAR)

Druck: CambridgeUniversity Press

Internet:http://www.ipcc.ch/

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IPCC TAR (2001)

Extrapolation of the CO2-Development

Used as Climate Model Forcing

Method:Different assumptions of energy consumption andeconomic developmentare expressed in CO

2

concentrations of the atmosphere.

A2: Scenario family describes a very heterogeneous world with slow and fragmented technological change.

B2: Scenario family describes a world in which the emphasis is on local solutions to economic, social andenvironmental sustainability.

B2: 80 ppm in 100 years (Interglacial: 80 ppm in 10,000 years)

A2: 400 ppm in 100 years

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IPCC TAR (2001)

Development of Global Surface Temperature

T(2100) = 2 - 4.5°C(comp. glacial reductionand time scale)

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IPCC TAR (2001)

Sea Level Rise due to Thermal Expansion

z(2100) = 30 - 50 cm(comp. glacial reduction)

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At least 7 of 9 models are considered. IPCC TAR (2001)

Regional Temperature Response

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Regional Precipitation Response

At least 7 of 9 models are considered. IPCC TAR (2001)

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Weather: Yesterday - Today - Tomorrow

Content:1) Introduction / Overview

2) Climate Development on Different Time Scales

3) Climate Modelling Principles

4) IPCC Third Assessment Report

5) OutlookNorth Atlantic deep water formationStorm frequency over North-western Europe

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North-Atlantic Deep Water Formation

North-Atlantic energy sources: 1/3 thermohaline circulation, 2/3 solar radiation

Noreiks (MPIM), 2002

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Model response indeep water formationis an prevailing topic in climate research.

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Storm Activity over North-Western Europe

Low pressure activity (geopotential metres) in 500 hPa over north-western Europe (40 - 70° N, 6° W - 20° E) Data: Climate simulation IS92a with ECHAM4(T42)

Quelle: Ulbrich, U. and M. Christoph (1999)

Basic message: Storm activity in winter will increase. Reduction between 1920 und 1950 corresponds with observed index.

Separation between storm strength and frequency is a prevailing topic in climate research.

Winter

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Summary

Statements inferred from the "Third Assessment Report":a) Weather tomorrow will change.

b) Summer and winter in Europe will be warmer.

c) Winter in Europe will become wetter, summer drier.

d) Winter storm activity will increase in winter.

Questions for the "Fourth Assessment Report":a) Climate response in North-Atlantic deep water formation?

b) Increase of storm frequency and/or strength in the Tropics and Europe?

c) Are weather extremes increasing?

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ENDE