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SST influence on extreme precipitation in Romania

SST influence on extreme precipitation in Romania. Roxana Bojariu, Ecaterina Ion-Bordei, Filippo Giorgi, Sara Rauscher and Xunqiang Bi. Radar – 23 martie 2007. Motivations. Physical mechanisms?. Flash flood episode of 22-23 March 2007: 38 villages affected 150 houses damaged

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SST influence on extreme precipitation in Romania

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  1. SST influence on extreme precipitation in Romania Roxana Bojariu, Ecaterina Ion-Bordei, Filippo Giorgi, Sara Rauscher and Xunqiang Bi

  2. Radar – 23 martie 2007 Motivations Physical mechanisms? • Flash flood episode of • 22-23 March 2007: • 38 villages affected • 150 houses damaged • 28 persons evacuated • 800 de ha of agricultural terrain damaged • 21 km of roadsdamaged • Flash flood episode of • 22-23 October 2007: • 100 villages affected

  3. Data • Daily Precipitation from 104 Romanian stations (1961-2001) (Administratia Nationala de Meteorologie, Romania); • Sea surface temperature (SST) – ERA40 (1961-2001) (ECMWF); • Mediterranean Cyclone Catalog :( Ecaterina Ion-Bordei). • numerical experiments with a regional climate model - RegCM 3, version 3 of RegCM (horizontal grid interval30 km) – with the help of Filippo Giorgi, Sara Rauscher and Xunqiang Bi . Metodology • Indices of extreme precipitation are computed from daily data for winter: • R95 (R98) - daily amounts equal or above the 95% percentile; • Canonical correlation analysis applied to the pairs total precipitation and SST, R95 and SST and R98 and SST; • Composites maps for 9 winter cases of Mediterranean cyclones crossing Romanian territory;

  4. 17 % 25% CCA analysis of observed extreme precipitation (PR95) and SST December to February R=0.73

  5. Time evolution of 1st CCA mode R=0.73

  6. 9 % 8 % CCA analysis of observed extreme precipitation (PR95) and SST March to May R=0.73

  7. +2 Temel Oguz, Joachim W. Dippner, Zerefsan Kaymaz, 2006:Climatic regulation of the Black Sea hydro-meteorological and ecological properties at interannual-to-decadal time scales. Journal of Marine Systems 60, 235–254. Interdecadal signal

  8. a) b) Numerical experiments: +2Exp minus CtrlExp ( 9 winter cases composites) Total column precipitable water Sea level pressure

  9. Z850 Z500 Numerical experiments: +2Exp minus CtrlExp ( 9 winter cases composites of geopotential heights)

  10. a)Obs. b)Ctrl Exp c) +2 Exp Observed and simulated precipitation composites - 9 winter cases

  11. Observed precipitation composite (mm/day) 1961-1979 minus 1980-1995 Simulated composites of 9 winter cases (mm/day) +2 Exp minus Ctrl Exp Observed and simulated composites for precipitation

  12. Conclusions • Extreme precipitation variability in Romania has a strong interdecadal component. • On regional scale, Black Sea SSTs seem to modulate precipitation and extreme precipitation, especially in the cold season • The cold season signal is robust and may be used in predictive methodologies and in projecting regional changes in precipitation under future climate conditions. • Further investigation is needed using both observed data and results from regional climate models to find other regional mechanisms (e.g. for the warm season).

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