Www.cru.uea.ac.uk Extremes in climate models Jean Palutikof Climatic Research Unit University of...

www.cru.uea.ac.uk

Extremes in climate models

Jean PalutikofClimatic Research Unit

University of East AngliaNorwich, UK

Workshop on Development of Scenarios of Climate Variability

and ExtremesVictoria, BC

www.cru.uea.ac.uk

1. Temperature extremesReferences: B.B. Brabson, D. H. Lister, J. P. Palutikof, P. D. Jones: Rapid rise of extreme temperatures in the 21st century. Submitted to Geophysical Research Letters

Brabson, B.B. and Palutikof, J.P., 2002: The Evolution of Extreme Temperatures in the Central England Temperature Record. Geophysical Research Letters, 29 (24), 10.1029/2002GL015964.

www.cru.uea.ac.uk

For observed Central England temperatures

www.cru.uea.ac.uk

GPD (peak-over-threshold)

• Three parameters: scale

shape

selected threshold

CDF:

• Three classes defined by the value of > 0 Long-tailed case

= 0 Exponential tail

< 0 Short-tailed case, finite

endpoint

• Return-period temperature:

1

11)(

xxF

FTT 11

www.cru.uea.ac.uk

GPD analysis of observed historical daily CET

• Analyses carried out on January/February warm and cold tails, and July/August hot and cool tails

• POT thresholds selected at each time step to include 5% values; separation distance of 4 days to ensure independence

• Based on 20-year overlapping periods, and looking at– the mean, , of all values, – 1SD above and below the mean

– the 10-year return period temperature, T10

www.cru.uea.ac.uk

1800 1900 2000-10

-5

0

5

10

Year

Tem

pera

ture

(°C

)

Jan/Feb

a

+0.18 ±0.23

+0.24 ±0.08

+0.36 ±0.05

+0.49 ±0.08

+1.05 ±0.47

1800 1900 2000

10

15

20

25

30

Year

July/Aug

bWarm T10

Mean + 1 S.D.MeanMean - 1 S.D.

Cool T10

+0.67 ±0.26

+0.19 ±0.05

+0.15 ±0.03

+0.11 ±0.05

+0.56 ±0.17

Tem

pera

ture

(°C

)

www.cru.uea.ac.uk

1900 1950 20000

0.1

0.2

0.3F

ract

ion

Winter Fractions by Type

Anticyclonic

Easterly

Southerly

Westerlya

1900 1950 20000

2

4

6

Avg

. T

emp.

(°C

)

Winter Temperature by Type

Anticyclonic

Easterly

Southerly

Westerly

b

1900 1950 20000

0.1

0.2

0.3

0.4

Fra

ctio

n

Winter Extreme Fractions

Anticyclonic

Easterly

Westerly

Southerly

c

1900 1950 20001.5

2

2.5

3

3.5

S.D

. (°

C)

Winter Temperature S.D.

Anticyclonic

Easterly

d

www.cru.uea.ac.uk

For future modelled Central England temperatures

www.cru.uea.ac.uk

Inter-experiment comparison of temperature extremes

• Annual extremes for:– January/February

• Highest TMIN (blue)• Lowest TMIN (black)

– July/August• Highest TMAX (red)• Lowest TMAX (green)

• Hadley Centre models:– HadCM3 A2– HadCM3 B2– HadCM2 (IS92a gg)

• For the Eastern England gridbox

• CET

www.cru.uea.ac.uk

Annual maxima/minima for SE England

www.cru.uea.ac.uk

• Three parameters: position

scale

shape

CDF:

• Three classes defined by the value of > 0 Long-tailed case

Fréchet

= 0 Exponential tailGumbel

< 0 Short-tailed case, finite end,

Weibull• Return-period temperature:

GEV distribution (annual maxima)

1

1exp)(x

xF

KT FT )ln(1

www.cru.uea.ac.uk

GEV analysis of modelled future daily ‘CET’

• For winter TMIN and summer TMAX• The Eastern England grid boxes• The HadCM3 A2 experiment• Based on 20-year overlapping periods, showing:

• T10 (warm tail) (warm tail)• the mean, smoothed with a 25-term filter (cold tail)• T10 (cold tail)

www.cru.uea.ac.uk

www.cru.uea.ac.uk

Moment-based contributions to HadCM3(A2): winter tmin (black; summer tmax (red)

www.cru.uea.ac.uk

Number of spells (Eastern England grid box)

www.cru.uea.ac.uk

Tmax as a function of soil moisture hot tail (red), mean (black), cold tail (blue)

www.cru.uea.ac.uk

Summary

• The GCMs predict a rapid rise in temperature over southern England

• Summer hot extremes rise much faster than the corresponding mean

• Soil moisture in HadCM3 provides the link between slowly rising means and rapidly rising extremes

www.cru.uea.ac.uk

2. High wind speeds and windstorm

C. Hanson et al., Proc. ‘Wind Effects on Trees, Karlsruhe, 2003

Hanson, C.E., and Palutikof, J.P., 2004: Variations in a UK cyclone climatology constructed from a group of nested climate models. Submitted to Geophysical Research Letters.

www.cru.uea.ac.uk

North Atlantic: Intensity Changes

A B

C D

Central Pressure (hPa)

Deepening Rate (hPa/12hr)

www.cru.uea.ac.uk

North Atlantic: Spatial Changes

www.cru.uea.ac.uk

UK Region: Intensity Changes

Central Pressure (hPa)

<940

<950

<960

<970

<980

<990

<1000

<1010

<1020

<1030

<1040

>1040

Nu

mb

er

of

De

pre

ss

ion

Ce

ntr

es

1000

800

600

400

200

0

1961-90

HadRM3

A2a 2070-99

B2a 2070-99

1961-90

HadAM3H

A2a 2070-99

B2a 2070-99

www.cru.uea.ac.uk

UK Region: Temporal Changes

HadRM3H baseline period (1961-90)

HadRM3H A2a experiment (2070-99)

HadRM3H B2a experiment (2070-99)

HadAM3H baseline period (1961-90)HadAM3H A2a experiment (2070-99)HadAM3H B2a experiment (2070-99)

≤1000hPa ≤970hPa

www.cru.uea.ac.uk

Summary

• Analysis of North Atlantic and UK cyclone activity in HadAM3H and HadRM3H has revealed no significant change in activity – frequency or intensity.

• HadAM3H indicates an increase in weaker events over south-east England.

• Potential for change in seasonality of the more intense events (HadRM3H).

• In general, the results are inconclusive.

www.cru.uea.ac.uk

A different approach allows identification of storm tracks

Work by the University of Koeln for the MICE project

www.cru.uea.ac.uk

HADCM3: Identification of Cyclones for the European SectorTrack density Winter (=ONDJFM)

A2a – CON_aCON_a Extreme cyclones > 99th percentile

Unit: Systems / Grid Unit / Winter

Contour interval 0.1 Contour interval 0.1

MICE – Work Progress of Partner 4 (UKOELN): U. Ulbrich, G. Leckebusch

MICE Project Meeting, Athens, 25.6.2003 - 27.6.2003

www.cru.uea.ac.uk

HADCM3: Identification of Cyclones for the European SectorCore Pressure Winter (=ONDJFM)

A2a – CON_aCON_a Extreme cyclones > 95th percentile

Unit: hPa

Contour interval 2.0 Contour interval 2.0



www.cru.uea.ac.uk

HadRM3: A2a-CON, Climate SignalWmax, 95 PercentilCON_a

Hr3_v.shp4.75 - 8.388.38 - 10.2510.25 - 12.512.5 - 16.6216.62 - 21.38

Countrys_gcl.shp

A2a – CON_a

Hr3_v.shp-1.5 - -0.5-0.5 - -0.26-0.26 - -0.24-0.24 - -0.06-0.06 - 0.060.06 - 0.120.12 - 0.130.13 - 0.250.25 - 0.380.38 - 1.63

Countrys_gcl.shp



www.cru.uea.ac.uk

HADCM3: Identification of Cyclones for the European Sector

Summary:

all systems: track density reduction, especially northern Europe (above the Norwegian Sea, Scandinavia)

extreme (> 95th or > 99th percentile) systems:track density reduction: Northern Europetrack density increase: South of 60N, Western Europedeepening of extreme cyclones

Scenarios A2 and B2 differ mainly with regard to extreme systems

A2: Increase of extreme systems in western central Europe



www.cru.uea.ac.uk

3. Rainfall extremes

Some results from the EU-funded MICE and PRUDENCE projects

Modelling the impacts of climate extremes

Prediction of Regional scenarios and Uncertainties for Defining EuropeaN

Climate change risks and Effects

www.cru.uea.ac.uk

How much can we believe what the models tell us?

A comparison for an RCM gridbox with many rain gauges

www.cru.uea.ac.uk

Southern England – 24 rain gauges in the central gridbox

HERTFORDSHIRE

51.2

51.4

51.6

51.8

52

52.2

52.4

-1.5 -1 -0.5 0 0.5 1

Longitude

Lat

itu

de

www.cru.uea.ac.uk

Number of wet and dry days

Wet days

0

30

60

90

0 0.1 0.5 0.8

Cutoff (mm)

Pe

rce

nt

fin

al n

um

be

r a

ll d

ay

s

Model 24 station 12 station 1 station

Dry days

0

10

20

30

40

50

60

70

0 0.1 0.5 0.8

Cutoff (mm)

Pe

rce

nt

fin

al n

um

be

r a

ll d

ay

s

Model 24 station 12 station 1 station

www.cru.uea.ac.uk

Number of days with high rainfall

Days with rainfall >10mm

1

1.5

2

2.5

3

3.5

4

0 5 10 15 20 25

Number of stations

Per

cen

t o

f al

l d

ays


0

0.2

0.4

0.6

0.8

0 5 10 15 20 25

Number of stations

Pe

rce

nt

all

da

ys


0

0.1

0.2

0.3

0.4

0 5 10 15 20 25

Number of stations

Per

cen

t al

l d

ays

www.cru.uea.ac.uk

What do the models tell us?

www.cru.uea.ac.uk

Precipitation indices: maximum length of dry spell per year (2070-99 minus 1961-90)

A2a scenario

A2a

B2a

A2a:– Longer by 15-30

days in centre and south east

– 10 days shorter over northern Europe

B2a:– Smaller changes than

A2a– wetter Eastern Med.

10oW 0o 10oE 20oE 30oE 40oE 30oN

35oN

40oN

45oN

50oN

-10

0

10

20

30


35oN

40oN

45oN

50oN

-10

0

10

20

30

www.cru.uea.ac.uk

Precipitation indices: start of drought(2070-99 minus 1961-90)

A2a scenario

A2a

B2a

A2a:– 5-10 days earlier

in future– No change over

much of northern Europe

B2a:– 3-5 days earlier

in future


35oN

40oN

45oN

50oN

-15

-10

-5

0

5

10

15


35oN

40oN

45oN

50oN

-15

-10

-5

0

5

10

15

www.cru.uea.ac.uk

Precipitation indices: end of drought(2070-99 minus 1961-90)

A2a scenario

A2a:– Generally no

change or slightly earlier end in future

– later over centre and south east

B2a:– Very similar to

A2a


35oN

40oN

45oN

50oN

-10

0

10

20

30


35oN

40oN

45oN

50oN

-10

0

10

20

30

www.cru.uea.ac.uk

Precipitation indices: max. 5-day running total(2070-99 minus 1961-90)

A2a scenario

A2a:– Lower by 10-20 mm

in future, particularly in west

– Wetter in centre and Adriatic

B2a:– Smaller changes

than A2a– Clearly wetter in Italy


35oN

40oN

45oN

50oN

-40

-20

0

20

40


35oN

40oN

45oN

50oN

-40

-20

0

20

40

www.cru.uea.ac.uk

Precipitation indices: summary

• Summer Mediterranean droughts likely to start earlier under A2a, particularly in south east Mediterranean

• Summer droughts in northern Europe likely to be slightly shorter under A2a

• Western and eastern Mediterranean drier in winter under A2a, Adriatic and central Italy wetter

• Under B2a all A2a changes reduced, Italy wetter

www.cru.uea.ac.uk

What can climate models tell us about extremes?

• Used appropriately, model data can be applied without intervening statistical downscaling to explore extremes, thus avoiding such issues as

• preservation of relationships in spatial and temporal fields• and whether or not all contributing forcing factors have been

taken into account

• Processing with techniques such as:• Extreme value analysis• Storm tracking algorithms

can yield valuable information

Www.cru.uea.ac.uk Extremes in climate models Jean Palutikof Climatic Research Unit University of...

Documents

Transcript of Www.cru.uea.ac.uk Extremes in climate models Jean Palutikof Climatic Research Unit University of...