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Regional climate change and hydrological impacts in Mediterranean river basins P.Lionello (University of Lecce, Italy) F.Giorgi (ICTP, Trieste, Italy)

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Presentation on theme: "Regional climate change and hydrological impacts in Mediterranean river basins P.Lionello (University of Lecce, Italy) F.Giorgi (ICTP, Trieste, Italy)"— Presentation transcript:

1 Regional climate change and hydrological impacts in Mediterranean river basins P.Lionello (University of Lecce, Italy) F.Giorgi (ICTP, Trieste, Italy)

2 Contents: Introduction Present trends Regional climate change Water balance for selected river basins Regional climate change and hydrological impacts in Mediterranean river basins

3

4 Ebro Rhone Po Nile 1700km Danube 3700km

5 Wet season (ONDJFM)Dry season (AMJJAS) mm/month Precipitation climatology 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 mean monthly terrestrial climatology. J. Climate, 12,

6 mm/(season · 50years) Acknowledgement: Xoplaki, 2002; Xoplaki et al., 2004 Wet season precipitation trend ( )

7 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 ( )

8 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

9 Downloaded from: Tim Osborn: North Atlantic Oscillation index data WINTER NAO (DJFM) Index ( )

10 Winter (DJF) Mediterranean precipitation anomalies with reference to the period from 1500 to 2002 Figure from Luterbacher et al., 2005, in Mediterranean Climate Variability, Lionello, Malanotte-Rizzoli, Boscolo eds, published by Elsevier, Amsterdam)

11 mm/(season · 50years) Acknowledgement: Xoplaki, 2002; Xoplaki et al., 2004 Dry season precipitation trend ( )

12 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 ( )

13 Change in Summer Precipitation (% change) CRU Observations ( ) minus ( )

14 (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

15 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 20 th 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

16 From Giorgi and Bi, GRL, 2005 REA Reliability Ensemble Average precipitation changes for the 21 st century (bars: A1B scenario; spread: A2 and B1 Scenarios)

17 Change in precipitation interannual variability (CV, minus , A1B-A2-B1) (CV, minus , A1B-A2-B1) WS >10% WS 0-10% DS >10% DS 0-10% DS % WS < -10% NEU SSA NEE MED CASTIB SAH WAF EAF SQF EQF SAF EAS SEA NAU SAU NAS CNA ENA WNA ALA GRL CAM AMZ CSA

18 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)

19 RegCM experiment design Global Model: Hadley Centre HadAMH –Dx = 1.25 lat x 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 – : Reference run – : Scenario run Scenarios: A2, B2 Giorgi, F., X. Bi and J.S. Pal, 2004 a and b

20 CRU Observed climatology CTR RegCM model WETWET SEASONSEASON SEASONSEASON DRYDRY

21 Precipitation A2-CTR Jan Feb Mar Apr May Jun Jul Aug Sep Oct Nov Dec mm

22 Mediterranean River basins Ebro PoCroatian rivers Greek rivers Turkish rivers Rhone

23 PO and Croatian rivers Precipitation Evaporation Water balance (P-E) - =

24 Ebro Precipitation Evaporation - = Water balance (P-E)

25 Greece and Turkey Precipitation Evaporation Water balance (P-E) - =

26 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

27 The Mediterranean appears to be particularly responsive to global change We cannot ignore this problem From Giorgi, GRL, 2006 Climate change Hot-Spots

28 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


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