Extremes and marine storms in the Mediterranean Sea P.Lionello, Univ. of Lecce, Italy 1 Intro: GEV and generalities examples from RON and sea level in Venice 2 some insight I): Storm surge trends for Venice 3 generalities on waves and wave modeling 4 some insight II): futures scenarios for storminess and implications for waves and surges...

Data gathering: long homogeneous series of data from observations or models Event definition: a set of independent event, the set should contain many items, but few of them are used EXTREME VALUE ANALYSIS is well established common paradigm return values for relatively long periods But many of other aspects are in practice mostly specific to the problem, and only general guidelines are available

4 NOV event SLP and U10 Surge and waves Cyclones (winds), waves and surges

algherocrotone pescara monopolimazara ponza la spezia  =0.30±0.14  =0.43±0.15  =0.07±0.28  =-0.10±0.22  =0.17±0.16  =0.02±0.17  =-0.10±0.19  =4.74  0.15  =4.82  0.18  =4.29  0.14  =3.70  0.11  =4.76  0.16  =4.66  0.14  =7.42  0.21

alghero crotone pescara monopoli mazara ponza la spezia

1940 to to to to 2000 GEV distribution Venice surge: Extreme values distribution

EXTREMES WAVES, SURGES IN THE ADRIATIC SEA IN A 2xCO 2 SCENARIO P.Lionello, F.Dalan, E.Elvini, A.Nizzero

The common element of wave and surges is WIND More intense cyclones Higher wind speeds Higher waves and storm surges Loss of lives, loss of properties, loss of economic resources, cultural and environmental heritages, increased costs of coastal defences

CONSEQUENCES ON WAVE FIELDS AND STORM SURGE A DOWNSCALING PROCEDURE APPLIED TO THE ADRIATIC SEA

SIMULATED PREDICTOR DYNAMICAL MODELS OF OCEAN WAVES AND STORM SURGES STATISTICAL MODEL SIMULATED WAVES AND SURGES 2) The surge level and the wave field are computed from the wind field using a barotropic (single layer) circulation model and a spectral wave model (WAM) The downscaling procedure consists of two steps. 1) A regional wind field is derived from the sea level pressure field (available every 6 hours) by CCA of the PCA prefiltered fields PREDICTOR: SLP PREDICTAND: U 10 SIMULATED PREDICTAND: U 10

downscaling T106 Observations downscaling T106 Observations The downscaling procedure has been tested applying it to the ERA-15 SLP data. The same period has also been simulated using directly the T106 winds. The downscaling produces a large improvement in the simulated Significant Wave Height and surge levels. However, levels during peak events remain underpredicted.

scenariomax100 years depth OBS CO 0.3 CTR   RESULTS: SIGNIFICANT WAVE HEIGHT

CO2 CTR CO2 CTR CO2 CTR MAXFREQUENCY100-YEAR RETURN VALUES

STORM SURGE

Venice: Frequency of surges East coast of England: Frequency of surges Figs from D.Camuffo, (1993)Theor.Appl.Climatol.47,1-14 Are the surges in Venice a result of recent climate changes? Is their frequency related to global processes?

Source: Report by P.Canestrelli Surges above 110cm level (reference: fixed reference level) Sea level rise Surges above 110cm level (reference: annual mean sea level) Trend in frequency/intensity of storm surges?

The observed trend is mostly produced by loss of ground level. This has no relation with more intense storms in a changed climate… however, a smaller trend could be present. Is this small trend an indication of what could be expected in a 2XCO2 CLIMATE?

scenariomax100 years depth OBS CO  8 CTR   RESULTS: SURGE

CO2 CTR CO2 CTR CO2 CTR MAXFREQUENCY100-YEAR RETURN VALUES

The CO2 scenario presents a marginally diminished wave activity in the southern Adriatic. The two scenarios present substantially equivalent extreme surge levels. There is a minor increase in the CO2 scenario. The doubled CO2 simulation is characterized with more extreme weather events, but the (significant) difference between the two scenarios is small, and not fully significant for Mediterranean region

THE END Clim. Res. (2002), 22, , Clim. Res. (2003) 23,