Drought in Europe

Drought in Europe
Sonia Seneviratne, Lukas Gudmundsson, Rene Orth, Henny van Lanen,
Kerstin Stahl, Lena Tallaksen, Stefan Brönnimann, Peter Greve, Bart van
den Hurk, Valerie Masson-Delmotte, Boris Orlowsky, Siegfried Schubert,
Irmi Seidl, Adriaan J. Teuling, Robert Vautard
Institute for Atmospheric and Climate Science, ETH Zurich, Switzerland
sonia.seneviratne@env.ethz.ch
GDIS meeting, Pasadena, December 11, 2014
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Outline
Drought drivers in Europe
New drought datasets & past vs future drought trends in Europe
Drought information: Linking drought indices to impacts
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
SST drivers for drought in Europe?
Literature review:
No clear evidence of role of large-scale modes of variability
for drought in Europe
Consistent with recent analyses on SST drivers of
precipitation and assessment of SPI predictability
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Drought drivers
No evidence for strong SST control on droughts in Europe
Precipita-on T2m SST Signal/Total variance on Interannual Time Scales
As estimated from 5 AGCMs, 60 ensemble members: annual means (1979-2011)
(Schubert et al. 2014, to be submitted)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Forecast skills
No substantial forecast skill compared to persistence forecast
beyond 1 month
First forecast lead time at which ROC skill score is
higher than persistence forecast (ECMWF system 4)
(Similar results with NMME: see e.g. presentation of K. Mo)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
(Dutra et al. 2014, HESS)
GDIS meeting
If no strong impact from SST forcing, what are possible sources
of predictability?
Land initialization (soil moisture, snow) can be important at lead
time of a few weeks to a few months
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Soil moisture memory in Europe
In some regions
and months:
substantial soil
moisture memory
up to 40 days, i.e.
can expand
forecasting window
(Orth and Seneviratne 2012, JGR)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Case study: Drought forecasting in Switzerland
Synthetic model study:
Soil moisture
forecasting
Much of the
predictability comes
from the initial soil
moisture
NB: Atmospheric
forecast can expand
skill beyond the time
window at which it is
skillful! (propagation
through soil moisture)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Case study: Drought forecasting in Switzerland
Synthetic model study:
Soil moisture
forecasting
Drier initial
conditions: higher
forecast skill
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Role of precipitation vs evapotranspiration for droughts
“Propagation” of meteorological drought to hydrological droughts is often
highlighted. But there are also different drivers!
Soil moisture
drought may be
more predictable
than meteorological
drought
Role of
evapotranspiration
also needs to be
considered
(Seneviratne 2012, Nature N&V)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Role of precipitation vs evapotranspiration for droughts
June 2003: Water balance in Rietholzbach
catchment (NE Switzerland)
Total water deficit
60%
Evapotranspiration
40%
Precipitation +
Runoff
[mm]
(Data from Seneviratne et al. 2012, WRR)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Role of precipitation vs evapotranspiration for droughts
Analysis for 3
catchments in
Europe
Evapotranspiration
amplifies summer
drought in Central
Europe
(Teuling et al. 2013, GRL)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Data requirements
Need for soil moisture and evapotranspiration information in addition to
precipitation is recognized by end users
Inquiry with fruit farmers in Switzerland: Which information would you need
to better prepare for drought risk? (in %, N=801)
additionally
needed
already used
soil moisture
evapotranspiration
precipitation
(S. Kruse, I. Seidl, WSL; DROUGHT-CH project)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Outline
Drought drivers in Europe
New drought datasets & past vs future drought trends in Europe
Drought information: Linking drought indices to impacts
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
New European drought datasets
ETH Products:
•  SPI and SPEI datasets 1950-2013 based on E-OBS (L. Gudmundsson)
•  Upscaling of runoff data in Europe 1950-2013
(Gudmundsson and Seneviratne, submitted to HESS)
•  Soil moisture product based on calibrated simple model (3
calibration functions, 5 parameters; single calibration for all of
Europe based on range of observation datasets), 1984-2013
(Orth and Seneviratne, submitted to ERL)
To be compared with EDO products (see presentation of J. Vogt)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Upscaled runoff product
(Gudmundsson and Seneviratne, submitted to HESS)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
SRI-1
Timeseries (1950-2013): Whole continent
Consistent SPI, SPEI and SRI timeseries
Strong decadal variability
(Gudmundsson and Seneviratne, EU-FP7 DROUGHT-RSPI Project)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Long-term trends
Trends show known dipole pattern
SPEI possibly overestimated (temperature-based Epot)
(Gudmundsson and Seneviratne, EU-FP7 DROUGHT-RSPI Project)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Robust assessment of global drought trends
Assessment based on 4 P
datasets, 11 Ep datasets, and 7 E
datasets using Budyko framework
as constraint
Consistent
result for
Europe
(Greve et al. 2014, Nature Geoscience)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Drought projections in Europe
Historical trends are consistent with projections
(Orlowsky and Seneviratne 2013, HESS)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Soil moisture product
(Orth and Seneviratne, submitted to ERL)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Soil moisture product
2003 was not the driest possible event: with full drying higher
temperatures could have occurred
(Whan et al., submitted)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Outline
Drought drivers in Europe
New drought datasets & past vs future drought trends in Europe
Drought information: Linking drought indices to impacts
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Relating physical drivers to impacts
(Blauhut, U. Freiburg)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Conclusions
No dominant role of SSTs in driving droughts in Europe, little
predictability beyond 1 month
Soil moisture initialization and propagation of meteorological forcing
can provide substantial added skill on this time scale
Evapotranspiration is a major driver for European droughts of
comparable magnitude to precipitation (about 50% for investigated
catchments)
New datasets provide retrospective estimates of precipitation,
streamflow and soil moisture deficits
Drying tendency in past decades in Mediterranean region consistent
with climate projections
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Forecast skills
NMME: Compare with persistence base line forecasts
(red: NMME is more skillful, dark red: stat sig at 10% level, Green : pers is more skillful)
SPI3 lead1
SPI3 lead2
SPI6 lead 3
Jan
April
July
Oct
(K. Mo, CPC)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Drought in Europe
1976-2006
Area affected by droughts [km2]
1,400,000
Mio people affected by drought
160
600,000
0
0
(European commission, 2007)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting
Soil moisture memory in Europe
Soil moisture memory is
often decreased when dry
periods are removed: i.e.
possibly more forecasting
potential in dry periods
(Orth and Seneviratne 2012, JGR)
11.12.2014
Sonia Seneviratne / IAC ETH Zurich
GDIS meeting