Regional climate change and hydrological impacts in Mediterranean river basins

P.Lionello (University of Lecce, Italy) F.Giorgi (ICTP, Trieste, Italy)

Contents:

•Introduction•Present trends•Regional climate change•Water balance for selected river basins

Regional climate change and hydrological impacts in Mediterranean river basins

Ebro

Rhone Po

Nile

1700km

Danube

3700km

Wet season (ONDJFM) Dry season (AMJJAS)

mm/month

Precipitation climatology 1961-1990

Graphics based on CRU climatology, interpolated from station data to 0.5 degree lat/lon grid ( New, M., M. Hulme and P. Jones, 1999: Representing twentieth-century space-time climate variability. Part I: Development of a 1961-90 mean monthly terrestrial climatology. J. Climate, 12, 829-856.

mm/(season · 50years)

Acknowledgement: Xoplaki, 2002; Xoplaki et al., 2004

Wet season precipitation trend (1950-1999)

Acknowledgement: Jacobeit, J., A. Dünkeloh & E. Hertig (2005): Mediterranean rainfall changes and their causes. In: Warnsignal Klima: Genug Wasser für alle? (ed. by J. Losan et al.), Hamburg.

Winter (DJF) precipitation trend (1951-2000)

Courtesy of E.Zorita

LINK to NAO

Correlation between the NAO index and precipitation (left) and air-temperature (right) in the cold season (DJF), derived from CRU NAO index and the NCEP reanalysis

Downloaded from:”Tim Osborn: North Atlantic Oscillation index data”http://www.cru.uea.ac.uk/~timo/projpages/nao_update.htm

WINTER NAO (DJFM) Index (1820-2005)

Winter (DJF) Mediterranean precipitation anomalies with reference to the period 1961-1990 from 1500 to 2002

Figure from Luterbacher et al., 2005, in “Mediterranean Climate Variability”, Lionello, Malanotte-Rizzoli, Boscolo eds, published by Elsevier, Amsterdam)

mm/(season · 50years)

Acknowledgement: Xoplaki, 2002; Xoplaki et al., 2004

Dry season precipitation trend (1950-1999)

Acknowledgement: Jacobeit, J., A. Dünkeloh & E. Hertig (2005): Mediterranean rainfall changes and their causes. In: Warnsignal Klima: Genug Wasser für alle? (ed. by J. Losan et al.), Hamburg.

Summer (JJA) precipitation trend (1951-2000)

Change in Summer Precipitation

(% change)

CRU Observations(1976-2000) minus (1951-1975)

(Alpert et al. GRL, Vol. 29,June 2002)

D1,D2 peaks in El-Nino years:1953,65,82/3,86/7

Italy: Trends in precipitation regimes

Summary: Present trends of precipitation

Large negative trend in winter precipitation, linked to the positive phase of NAO, but somehow larger than what suggested by the positive NAO trend

No clear evidence of a trend in summer precipitation for the entire Mediterranean if the whole second half of the 20th century is considered… but there are suggestions of a drier summer season during the last two decades

Change of statistical distribution of precipitation events: percent-wise reduction/increase of the frequency of intense/weak precipitation events in Italy

From Giorgi and Bi, GRL, 2005From Giorgi and Bi, GRL, 2005

REA Reliability Ensemble Average precipitation REA Reliability Ensemble Average precipitation changes for the 21changes for the 21stst century century

(bars: A1B scenario; spread: A2 and B1 Scenarios)(bars: A1B scenario; spread: A2 and B1 Scenarios)

Change in precipitation interannual variabilityChange in precipitation interannual variability (CV, 2080-2099 minus 1960-1979, A1B-A2-B1)(CV, 2080-2099 minus 1960-1979, A1B-A2-B1)

WS >10%WS >10%

WS 0-10%WS 0-10%

DS >10%DS >10%

DS 0-10%DS 0-10%

DS 0- -10%DS 0- -10%

WS < -10%WS < -10%

NEUNEU

SSASSA

NEENEE

MEDMEDCASCAS TIBTIB

SAHSAH

WAFWAF EAFEAF

SQFSQF

EQFEQF

SAFSAF

EASEAS

SEASEA

NAUNAU

SAUSAU

NASNAS

CNACNA

ENAENAWNAWNA

ALAALAGRLGRL

CAMCAM

AMZAMZ

CSACSA

Summary: regional analysis of global simulations for the Mediterranean region

Increasingly drier conditions both in the wet and in the dry season (~20%)

Increasingly irregular precipitation in both seasons(~ 40% in the dry season)

RegCM experiment design

• Global Model: Hadley Centre HadAMH– Dx = 1.25 lat x 1.875 lon– SST from HadCM3 run– Coupled sulfur model

• Regional model: ICTP RegCM– Dx = 50 km– SST, GHG and sulfate from

HadAMH– aerosol effects

• Simulation periods– 1961-1990 : Reference run– 2071-2100 : Scenario run

• Scenarios: A2, B2

Giorgi, F., X. Bi and J.S. Pal , 2004 a and b

CRU Observed climatology

CTR RegCM model

WET

SEASON

SEASON

DRY

Precipitation A2-CTR Jan

Feb

Mar

Apr

May

Jun

Jul

Aug

Sep

Oct

Nov

Dec

mm

Mediterranean River basins

Ebro

Po Croatian rivers

Greek rivers

Turkish rivers

Rhone

PO and Croatian riversP

reci

pit

atio

n

Eva

po

rati

on

Wat

er b

alan

ce (

P-E

)

-

=

EbroP

reci

pit

atio

n

Eva

po

rati

on

-

=

Wat

er b

alan

ce (

P-E

)

Greece and TurkeyP

reci

pit

atio

n

Eva

po

rati

on

Wat

er b

alan

ce (

P-E

)

-

=

Summary: water balance and river basins in future climate scenario

•Reduced precipitation over most of the Mediterranean, but in the North-West area in winter•Much drier summer season in the Ebro, Po and Croatian river basins•Drier autumn for Greek and Turkish rivers•Larger climate change signal for higher GHG concentration

The Mediterranean appears to beThe Mediterranean appears to beparticularly responsive to global change particularly responsive to global change

We cannot ignore this problemWe cannot ignore this problem

From Giorgi, GRL, 2006From Giorgi, GRL, 2006

Climate change Climate change Hot-SpotsHot-Spots

Regional climate change and hydrological impacts in Mediterranean river basins

Special acknowledgements to:Dr. E. Xoplaki and Prof. J.Jacobeit, for the figures that they provided and to Mrs.G.Vicentini for the graphics

P.Lionello (University of Lecce, Italy) F.Giorgi (ICTP, Trieste, Italy)

Thanks for your attention

email: piero.lionello@unile.it