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The European flooding of summer 2002 and its global connections

The European flooding of summer 2002 and its global connections. Mike Blackburn, Brian Hoskins, Pete Inness, Julia Slingo Centre for Global Atmospheric Modelling, The University of Reading, UK. Flooding in Central Europe. European Precipitation (percent of normal). JJA 2002. August 2002.

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The European flooding of summer 2002 and its global connections

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  1. The European floodingof summer 2002and its global connections Mike Blackburn, Brian Hoskins, Pete Inness, Julia Slingo Centre for Global Atmospheric Modelling, The University of Reading, UK

  2. Flooding in Central Europe

  3. European Precipitation(percent of normal) JJA 2002 August 2002

  4. July Drought in India

  5. Indian Precipitation:summer totals Rainfall for the period 1 June to 30 Sept., 2002 Monsoon Online: www.tropmet.res.in/~kolli/MOL Source: K. Rupa Kumar & J.V. Revadekar

  6. All-India Precipitation:seasonal evolution Daily total (mm) Daily accumulation Source: K. Rupa Kumar & J.V. Revadekar

  7. Niño 3.4 Index for JJA Niño 3.4 area: 170W-120W, 5N-5S Start of El Niño in the Pacific

  8. Could there be a link between these events? Theoretical? Historical correlation of interannual variability?

  9. Full model: global heating and orography Idealised monsoon heating (25°N), no orography Idealised monsoon heating (10°N), no orography Obs. JJA ω(477hPa) Monsoon / Mediterranean linkIdealised modelling:Rodwell & Hoskins (1996) Pressure, wind (325K) Mid-level descent ω(477hPa)

  10. Rodwell & Hoskins (1996)continued… Seasonal evolution of Mediterranean descent, 22:42°N, 8-37°E 477hPa ωfrom ECMWF analyses, 1994

  11. Indian monsoon rainfallandSouthern European Descent (JJA) • All-India rainfall index, 1958-2000 • NCEP/NCAR Reanalysis ω at 500hPa, global • Interannual variability is correlated

  12. Indian monsoon rainfallandSouthern European Descent (July) • NCEP/NCAR Reanalysis ω 35:45°N 0:30°E • Correlation coefficient 0.39 (1958-2000) • Higher correlation by crudely including a Pacific SST index • But no correlation of AIR with European rainfall

  13. Niño 3.4 SST • All India rainfall • w500 S. Europe [35-45N,0-30E] • CRU Precipitation S.Europe Correlations between: All-India rainfall and S. European descent July 1958-2002 (not detrended) July 1958-1998 . N34 AIR w500 CRU N34 -0.41 -0.38 0.31 AIR -0.41 0.39 -0.18 w500 –0.38 0.39 -0.61 CRU 0.31 -0.18 -0.61 - All time-series detrended -

  14. ω 500hPa : Dry monsoon composites for July All-India rainfall : 3 driest months July 1972, 1987, 2002 All-India rainfall : 7 driest months (exceeding 1 std-devn) • NCEP/NCAR reanalysis data captures the local Indian ω anomaly • Ascent anomaly over southern Europe • El Niño signal in Pacific (not shown)

  15. 200hPa Geopotential Height patterncorrelating withSouthern European Rainfall (JJA) • CRU land precipitation 35:45°N 0:30°E • NCEP/NCAR Reanalysis height • European Blocking pattern

  16. Sea level Pressure patterncorrelating withSouthern European Rainfall (JJA) • CRU land precipitation 35:45°N 0:30°E • NCEP/NCAR Reanalysis msl pressure • European Blocking pattern

  17. What happened during Summer 2002?

  18. 2002 monthly anomalies - 200hPa Height June July August September

  19. Streamfunction anomaly at σ = 0.2101 July/August 2002 (m2s-1) NCEP/NCAR Reanalysis data

  20. Downstream DevelopmentMeridional wind anomaly 250hPa, 45-60N 26 July – 26 Aug. JA 2002

  21. 1st 3rd 5th 7th 9th 11th Downstream Development 250hPa StreamfunctionECMWF analyses, 12UTC1-11 August 2002 • NWesterly flow over UK into the Mediterranean, 9-11th Aug. • A weather system followed this track and developed over Italy • Then tracked NE bringing 150mm rain to much of central Europe

  22. Animation for early August:Downstream Development ECMWF analyses

  23. Conclusions • Multiple influences on S. European summer variability • Theoretical and weak historical link to Indian monsoon • Importance of European blocking • Experimentation needed to determine causality for a single event/season:  idealised model with prescribed tropical forcing  GCM with realistic variability & teleconnections? • Extreme events:  large signals  stochastic component of precipitation

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