The European flooding of summer 2002 and its global connections
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The European floodingof summer 2002
and its global connections
Mike Blackburn, Brian Hoskins,Pete Inness, Julia Slingo
Centre for Global Atmospheric Modelling,
The University of Reading, UK
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Flooding in
Central Europe
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European Precipitation(percent of normal)
JJA 2002 August 2002
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July Drought
in India
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Indian Precipitation:summer totals
Source: K. Rupa Kumar & J.V. Revadekar
Monsoon Online: www.tropmet.res.in/~kolli/MOL
Rainfall for the period 1 June to 30 Sept., 2002
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All-India Precipitation:seasonal evolution
Source: K. Rupa Kumar & J.V. Revadekar
Daily total (mm) Daily accumulation
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Start of El Niño
in the Pacific
Niño 3.4 Index for JJA
Niño 3.4 area: 170W-120W, 5N-5S
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Theoretical?
Historical correlation of interannual variability?
Could there be a link between these events?
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Monsoon / Mediterranean link
Idealised modelling:Rodwell & Hoskins (1996)
Mid-level descent ω(477hPa)
Pressure, wind (325K)
Full model: global heating
and orography
Idealised monsoon heating
(25°N), no orography
Idealised monsoon heating
(10°N), no orography
Obs. JJA ω(477hPa)
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Rodwell & Hoskins (1996)continued…
Seasonal evolution of Mediterranean descent, 22:42°N, 8-37°E
477hPa ω from ECMWF analyses, 1994
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All-India rainfall index, 1958-2000
NCEP/NCAR Reanalysis ω at 500hPa, global
Interannual variability is correlated
Indian monsoon rainfalland
Southern European Descent (JJA)
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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
Indian monsoon rainfalland
Southern European Descent (July)
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Correlations between:
. 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
July 1958-1998
•Niño 3.4 SST•All India rainfall•w500 S. Europe [35-45N,0-
30E]
•CRU Precipitation S.Europe
- All time-series detrended -
All-India rainfall and S. European descentJuly 1958-2002 (not detrended)
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ω 500hPa : Dry monsoon composites for July
NCEP/NCAR reanalysis data captures the local Indian ω anomaly
Ascent anomaly over southern Europe
El Niño signal in Pacific (not shown)
All-India rainfall : 3 driest monthsJuly 1972, 1987, 2002
All-India rainfall : 7 driest months(exceeding 1 std-devn)
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CRU land precipitation 35:45°N 0:30°E
NCEP/NCAR Reanalysis height
European Blocking pattern
200hPa Geopotential Height patterncorrelating with
Southern European Rainfall (JJA)
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CRU land precipitation 35:45°N 0:30°E
NCEP/NCAR Reanalysis msl pressure
European Blocking pattern
Sea level Pressure patterncorrelating with
Southern European Rainfall (JJA)
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What happened during Summer 2002?
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2002 monthly anomalies - 200hPa Height
September
JulyJune
August
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NCEP/NCAR Reanalysis data
Streamfunction anomaly at σ = 0.2101 July/August 2002
(m2s-1)
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Downstream DevelopmentMeridional wind anomaly 250hPa, 45-60N
JA 2002 26 July – 26 Aug.
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Downstream Development
1st
3rd
5th
7th
9th
11th
250hPa Streamfunction
ECMWF analyses, 12UTC
1-11 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
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Animation for early August:Downstream Development
ECMWF analyses
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ConclusionsMultiple 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