Adv. Geosci., 12, 153–158, 2007
www.adv-geosci.net/12/153/2007/
© Author(s) 2007. This work is licensed
under a Creative Commons License.
Advances in
Geosciences
Winter precipitation and cyclones in the Mediterranean region:
future climate scenarios in a regional simulation
P. Lionello1 and F. Giorgi2
1 University
2 ICTP,
of Salento, Lecce, Italy
Trieste, Italy
Received: 5 March 2007 – Revised: 6 July 2007 – Accepted: 22 October 2007 – Published: 16 November 2007
Abstract. Future climate projections show higher/lower
winter (Dec-Jan-Feb) precipitation in the northern/southern
Mediterranean region than in present climate conditions.
This paper analyzes the results of regional model simulations
of the A2 and B2 scenarios, which confirm this opposite precipitation change and link it to the change of cyclone activity.
The increase of the winter cyclone activity in future climate
scenarios over western Europe is responsible for the larger
precipitation at the northern coast of the basin, though the
bulk of the change is located outside the Mediterranean region. The reduction of cyclone activity inside the Mediterranean region in future scenarios is responsible for the lower
precipitation at the southern and eastern Mediterranean coast.
1
Introduction
Previous studies, based both on global and regional simulations show opposite changes of winter (Dec-Jan-Feb) precipitation in different part of the Mediterranean region (Giorgi
and Lionello, 2007). In most simulations, precipitation is
projected to increase in a relatively narrow band in the northern part and to decrease in the rest, with very large reductions in some areas at the western (Morocco) and eastern
(Middle Est) border of the Mediterranean region. Figure 1
shows the projected percentage precipitation change according to the MGME (Multi Global Model Ensemble) for the
A2 (top) and B1 (bottom) scenarios. These public data,
which are stored at the Program for Climate Model Diagnosis
and Intercomparison (PCMDI, http://www-pcmdi.llnl.gov),
include the results of a large set of global climate simulations carried out with different models by about 20 research
groups for the 20th and 21st century under different greenhouse gas forcing scenarios as a contribution to the fourth
Correspondence to: P. Lionello
(piero.lionello@unile.it)
Assessment Report (AR4) of the Intergovernmental Panel on
Climate Change (IPCC). The transition line between positive
and negative change crosses the northern part of the Mediterranean region, and its position depends little on the emission
scenario, while the intensity of the negative (positive) change
in the southern Mediterranean (central and northern Europe)
dramatically increases with the emission level.
This study analyzes three 30-year regional climate simulations, one for present day conditions (1961–1990) (CTR
experiment) and two for future conditions (2071–2100) carried out with the regional climate model RegCM under the
IPCC A2 and B2 emission scenarios. The A2 is a high emission scenario, lying towards the high end of the IPCC range,
while the B2 is a low emission scenario lying towards the
low end of the range.
The aim of this study is to discuss the link between
changes of winter precipitation and of cyclonic activity in
this regional simulation for producing a consistent overall
picture of climate change projection for both quantities in
the Mediterranean area.
2
The RegCM model: present climate simulation
In this study, the RegCM model grid spacing is 50 km and
the model domain covers the European region and adjacent oceans. The model is driven at the lateral boundaries
by meteorological fields from the Hadley Centre global atmospheric model HadAM3H (1.25×1.875 lat-lon horizontal
resolution). Sea surface temperatures (SSTs) are from corresponding simulations with the Hadley Centre global coupled
model HadCM3. For more information on the model and for
a general discussion of the simulations, the reader is referred
to Giorgi et al. (2004a, b), for the discussion of the cyclone
climate change signal to Lionello et al. (2007).
Figure 2 compares the winter CRU (Climate Research
Unit, East Anglia University, (New et al., 2000)) and the CTR
Published by Copernicus Publications on behalf of the European Geosciences Union.
154
Lionello P. and Giorgi F.: Precipitation and cyclones
P. Lionello and F. Giorgi: Precipitation and cyclones
Lionello P. and Giorgi F.: Precipitation and cyclones
cyclone
ch Unit,
TR simmodel to
ding the
drier ind, espe-
ajectory
ea Level
ed to the
and-pass
s of the
led syne littera-
ECMWF
he CTR
ntitative
a, except
lation to
Mediterngitude,
yclones,
tracking
ng of the
of steepAll the
mum are
ny small
pression.
he same
ted with
ults in a
pressure
per than
comparmulation
stretchtern Eunumber
orrelated
ch overrecipitaproduce
herwise,
ver large
n are remap of
rack inain. The
Fig. 2. Winter precipitation according to the CRU data (top) and to
Fig. 2.theWinter
precipitation
to the
CRU data
CTR simulation
of theaccording
RegCM model
(bottom).
Units:(top)
mm.and to
Fig. 3. Synop
the CTR simulation of the RegCM model (bottom). Units: mm.
the CTR simu
Fig. 1. Winter (Dec-Jan-Feb) multi model average (MGME) precipFig. 1. Winter (Dec-Jan-Feb) multi model average (MGME) preitation percentage change in the Mediterranean region: A2 scenario
cipitation percentage change in the Mediterranean region: A2 sceminus present climate (top) and B1 scenario minus present climate
nario minus present climate (top) and B1 scenario minus present
(bottom).
climate (bottom).
effect of the
ridges
at the northern
Bordermodel
of the
simulation
and mountain
it shows the
capability
of the RegCM
region the
is responsible
for the number
of cytoMediterranean
reproduce correctly
observed climatology,
including
clone
centers
along
North
East
coast
ofthe
thedrier
basin
the
maxima
along
the the
coasts
and and
on the
Alps,
and
in fig.4.
However,
thethe
tracking
algorithm
has been applied
interior
areas,
although
maxima
are underestimated,
esto the along
band-pass
filteredGreek
fields,and
so Turkish
that thecoasts.
cyclone trajecpecially
the western
tory
differ from
those that
would
be identified
in the
Thefeatureis
cyclone activity
is analyzed
using
a cyclone
trajectory
original
SLP
fields.
The
15hPa
threshold
has
been
adopted
identification algorithm and computing the SLP (Sea Level
for fig.3standard
in orderdeviation.
to includeBoth
onlymethods
intense are
cyclone,
Pressure)
appliedlikely
to theto
contribute
significantly
to
the
precipitation
monthly
total.
SLP fields which have been pre-processed with a band-pass
(1–7 day) Lanczos digital filter. The strong features of the
band-pass filtered SLP standard deviation (here called synoptic signal) maps are often called storm tracks in the litterature.
3 Climate change signal in the RegCM simulations
Figure 3 shows the synoptic signal of the ERA-40
(ECMWF Re-Analysis, Simmons and Gibson, 2000) and of
The
winter
precipitation
change
in the
RegCM
simuthe
CTR
simulation.
The climate
comparison
shows
a good
quantilations substantially confirms the results of the MGME analAdv. Geosci., 12, 153–158, 2007
ysis1 and it shows contrasting changes in the Northern part,
to become
wetter,
and of
the the
southern
part, projected
tative projected
agreement
over large
parts
Mediterranean
area,
to become drier. Changes increase with the emission level
except(they
overareTurkey.
There
is
a
tendency
of
the
CTR
simularger in the A2 than in the B2 scenario, where they
lation are
to overestimate
synoptic
outside
significant onlythe
in small
areas)signal
and aremostly
particularly
sig-the
Mediterranean
region
over eastern
Europeover
(East
20 E
nificant in the
A2 scenario
being positive
theof
Alps
andlonnorthern
Adriatic
Coastand
on one
negative At the
gitude,theexcept
over
Greece)
the hand,
Blackand
Sea.
coast
of Turkeyproduces
and of Middle
on the
TheMediterranean
identification
algorithm
a listeast,
of cyclones,
other hand. Figs.5 shows the statistically significant changes
with the
SLP minima positions and values. The tracking
at a 90% confidence level according to a Mann-Whithey test.
method Also
(Lionello
et al.,activity
2002)the
is Mediterranean
based on partitioning
of the
for cyclone
is a transition
slp fields
in
depressions
by
the
identification
of
sets
of
steepregion with an intensification on its north-western area and a
est descent
paths
to the
slpsynoptic
minimum.
reduction
overleading
the eastern
area,same
both as
signalAll
and the
of by
cyclone
centers
are concerned
(figs.6minimum
and 7). In are
pointsnumber
crossed
a path
leading
to the same
Fig.7toonly
deeper than 15hPa
are included.
assigned
the minima
same depression.
Subsequently,
anyNote
small
that, however, the area where the largest intensification of
cyclone activ
it is associate
track over th
These cha
herent. It is
sociated with
associated to
surrounding
all intense ra
of a cyclone,
air to the loc
2001).
The strong
depression is merged into the closest large size depression. tation is confi
1
of total seas
The B2
scenario by
usedjoining
in this study
is not available
in same
the
A trajectory,
obtained
the location
of the
MGME
note that maps,
B1 and B2
similar, with
low pressuredataset.
centerHowever,
in successive
is are
associated
with tic signal an
550 and 600ppm CO concentration in 2100, respectively.
the CTR sim
the evolution of each depression. The procedure results in a
trajectory, an initial and final point, a sequence of pressure
minima, and of areas covered by the cyclone.
Figure 4 shows the density of cyclone centers deeper than
15 hPa in the band-pass filtered ERA-40 and the CTR simulation fields. The comparison between the two figures shows
that the CTR simulation overestimates the number of cyclones over an area stretching from central Europe to Turkey
www.adv-geosci.net/12/153/2007/
yclones
P. Lionello and F. Giorgi: Precipitation and cyclones
3
U data (top) and to
m). Units: mm.
Fig. 3. Fig.
Synoptic
signal
according
data(top)
(top)
3. Synoptic
signal
accordingtotothe
the ERA-40
ERA-40 data
andand
to to
thesimulation
CTR simulation
of the
RegCMmodel
model(bottom).
(bottom). Units:
the CTR
of the
RegCM
Units:hPahPa
e Northern part,
n part, projected
cyclone activity takes place is outside the Mediterranean and
e emission level
it is associate with an intensification of the mid-latitude storm
ario, where they
acrosstrack
south-eastern
Europe. It will be shown in the next
over the north-east Atlantic.
particularly sigSect.
3
that
the
number
of cyclones at the southern border of
ver the Alps and
These changes of precipitation and cyclone activity are coin thisherent.
area isIt is
correlated
with
precipitation
over isGreece
negative At the
well known
that the
the passage
of a cyclone
asdle east, on the
and Turkey.
Suchrain.
overestimation,
combined
withis often
the unsociated with
In the Mediterranean
region this
nificant changes
associatedoftoprecipitation,
the advection of
humid air
against
the Mediterslopes
derestimation
suggests
that
eastern
nn-Whithey test.
basin. In
fact,rain
it hasinbeen
almost
raneansurrounding
cyclones the
produce
less
the shown
modelthatsimulation
an is a transition
intense rain
events arethe
in coincidence
withcyclone
the presence
than inallreality.
Otherwise,
frequency of
centers
estern area and a
of a cyclone, positioned so that its circulation advects humid
is roughly
correct
over
large
parts
of
the
domain.
optic signal and
air to the location where precipitation occurs (Jansá et al. ,
figs.6 and 7). In
2001). characterizing the Mediterranean region are reFeatures
included. Note
link between
position
of cyclones
producedThebystrong
the model
results
in Figs.
3 and and
4. precipiThe map
ntensification of
tation is confirmed computing the Spearman rank-correlation
of the ofwinter
synoptic
signal
(Fig.
3)
shows
the
storm
track
total seasonal precipitation in selected areas with synopt available in the
intensification
on
the
lee
of
the
Alps
and
Atlas
Mountain.
tic signal and frequency of cyclones deeper than 15hPa for
are similar, with
The effect
of the
mountain
at the northern
pectively.
the CTR
simulation.
Theridges
geographical
distributionBorder
of the of
the Mediterranean region is responsible for the number of
cyclone centers along the North and East coast of the basin
in Fig. 4. However, the tracking algorithm has been applied
to the band-pass filtered fields, so that the cyclone trajectory
features differ from those that would be identified in the original SLP fields. The 15hPa threshold has been adopted for
Fig. 3 in order to include only intense cyclone, likely to contribute significantly to the precipitation monthly total.
www.adv-geosci.net/12/153/2007/
4
155
Lion
Fig. 5. Winte
nus A2 scena
4. Cyclone
frequency
15hPa) according
thethe
Fig. 4.Fig.Cyclone
(deeper
than (deeper
15 hPa)than
frequency
accordingto to
denote drier c
8
number
of
ERA-40
data (top)
to theCTR
CTRsimulation.
simulation. Units:
10 10
ERA-40
data (top)
andand
to the
Units:
number
changes are s
month
.
Data
have
been
smoothed
on
squared
areas
minima km
of minima km−2 month−1 . Data have been smoothed on squared cording to the
with size 3 and 11 grid points for ERA-40 and CTR, respectively.
areas with size 3 and 11 grid points for ERA-40 and CTR, respectively.
cyclone activity responsible for winter precipitation on the
continental part of Italy (including the southern side of the
3 Climate
change signal in the RegCM simulations
Alps) and the Croatian coast of the Adriatic Sea is shown in
fig.8. The seasonal value of precipitation in these two areas
(whereprecipitation
it is projected climate
to increase)
is correlated
with the synThe winter
change
in the RegCM
simusignal and the
numberthe
of central
lationsoptic
substantially
confirms
resultspressure
of the minima
MGMEover
analthe western Mediterranean and western Europe (fig.8). The
ysis1 and
it shows contrasting changes in the Northern part,
Mediterranean coast of Turkey and the eastern Coast of the
projected
to become
wetter,
and the
southern ispart,
projected
Mediterranean
(where
the winter
precipitation
projected
to
to become
drier.
Changes
increase
the emission
level
diminish)
show
a different
pattern: with
precipitation
over those
(they two
are regions
larger isincorrelated
the A2 with
thansynoptic
in the signal
B2 scenario,
in a regionwhere
including
the whole
Mediterranean
and north
and with
they are
significant
only
in small areas)
andAfrica
are particularly
the frequency
of cyclone
centers
the northern
coast
significant
in the A2
scenario,
beingalong
positive
over the
Alps
of the Mediterranean (fig.9). Therefore, the comparison beand the northern Adriatic coast on one hand, and negative
tween fig.8 and fig.9 shows the different positions of cyclone
at the Mediterranean coast of Turkey and of Middle east, on
the other hand. Figure 5 shows the statistically significant
changes at the 90% confidence level according to the MannWhithey test.
1 The B2 scenario used in this study is not available in the
MGME dataset. However, note that B1 and B2 are similar, with
550 and 600 ppm CO2 concentration in 2100, respectively.
Adv. Geosci., 12, 153–158, 2007
centers and o
ern and sout
Using the
preting the
to the concl
number of c
mainly in it
change of p
change in th
instead caus
storm track o
4 Conclus
The analysis
B2 scenario
g to the
mber of
ed areas
tively.
on the
of the
own in
o areas
he syna over
). The
of the
cted to
r those
ion ind with
coast
on beyclone
156
Lionello P. and Giorgi F.: Precipitation and cyclones
Fig. 5. Winter precipitation climate change signal. Top: CTR minus A2
scenario.
Bottom: CTR
minuschange
B2 scenario.
values
Fig.
5. Winter
precipitation
Climate
signal. Positive
Top: CTR
midenote
drier
conditions
in
climate
scenarios.
In
the
colored
areas
nus A2 scenario. Bottom: CTR minus B2 scenario. Positive values
changesdrier
are statistically
significant
at the 90% In
confidence
levelareas
acdenote
conditions in
climate scenarios.
the colored
cording to
Mann-Whitney
test. Units:
mm. confidence level acchanges
arethe
statistically
significant
at the 90%
cording to the Mann-Whitney test. Units: mm.
Also for cyclone activity the Mediterranean is a transition
region with an intensification on its north-western area and a
centers and of cyclone activity that produce rain in the northreduction over the eastern area, both as synoptic signal and
ern and south-eastern coasts of the Mediterranean.
number of cyclone centers are concerned (Figs. 6 and 7). In
Using the spatial distribution of the correlation for interFig. 7 only minima deeper than 15 hPa are included. Note
preting the climate change signal shown in figs.5-7 brings
that, however, the area where the largest intensification of
to the conclusion that the reduction of cyclone activity and
cyclone activity takes place is outside the Mediterranean and
number of cyclones inside the Mediterranean region (and
it is associate with an intensification of the mid-latitude storm
mainly in its eastern part) is responsible for the negative
track over the north-east Atlantic.
change of precipitation in its eastern part. The positive
Theseinchanges
of precipitation
andMediterranean
cyclone activity
are cochange
the northern
part of the
region
is
herent.
It
is
well
known
that
the
passage
of
a
cyclone
is asinstead caused by the increased strength of the mid-latitude
sociated
with
rain. In mostly
the Mediterranean
regionitself.
this is often
storm
track
occurring
outside the region
associated to the advection of humid air against the slopes
surrounding the basin. In fact, it has been shown that almost
4all intense
Conclusions
rain events are in coincidence with the presence of
a cyclone, positioned so that its circulation advects humid air
The
regional
climate simulations
ofetthe
and
to theanalysis
locationofwhere
precipitation
occurs (Jansá
al.,A2
2001).
B2 scenario confirms the global ensemble results and it
Adv. Geosci., 12, 153–158, 2007
andF.:
F. Precipitation
Giorgi: Precipitation
and cyclones
LionelloP.P.Lionello
and Giorgi
and cyclones
Fig. 6. Synoptic signal. Top: A2 minus CTR scenario. Bottom:
B2 minus
CTR scenario.
Positive
values
denote
larger CTR
synoptic
Fig.
6. Synoptic
Climate change
signal.
Top:
A2 minus
scesignal
in
climate
scenarios.
In
the
colored
areas
changes
stanario. Bottom: B2 minus CTR scenario. Positive valuesare
denote
tistically
significant
at in
theclimate
90% confidence
according
the
larger
synoptic
signal
scenarios. level
In the
coloredtoareas
Mann-Whitney
test. Units:
HPa. at the 90% confidence level acchanges
are statistically
significant
cording to the Mann-Whitney test. Units: HPa.
The strong link between position of cyclones and precipishows wetter winter conditions at the northern boundary of
tation is confirmed computing the Spearman rank-correlation
the Mediterranean region and drier along the southern and
of total seasonal precipitation in selected areas with synopeastern coast of the basin. A purpose of this paper is to extic signal and frequency of cyclones deeper than 15 hPa for
plain such changes in the precipitation field (fig.5) on the bathe CTR simulation. The geographical distribution of the
sis of changes in synoptic signal (fig.s6) and cyclone number
cyclone activity responsible for winter precipitation on the
(fig.7) because of the respective correlation fields shown in
continental part of Italy (including the southern side of the
figs.8 and 9.
Alps) and the Croatian coast of the Adriatic Sea is shown in
The high resolution of the RegCM simulation allows the
Fig. 8. The seasonal value of precipitation in these two areas
identification of cyclones and the evaluation of the climate
(where it is projected to increase) is correlated with the synchange signal. Cyclone activity is projected to become
optic signal and the number of central pressure minima over
weaker over the eastern Mediterranean and stronger in the
the western Mediterranean and western Europe (Fig. 8). The
north-western areas. In fact, the north western Mediterranean
Mediterranean coast of Turkey and the eastern coast of the
is partially affected by the intensification of the mid-latitude
Mediterranean (where the winter precipitation is projected to
storm-track which occurs over central and western Europe in
diminish) show a different pattern: precipitation over those
the scenario simulations.
www.adv-geosci.net/12/153/2007/
Fig. 7.
minima
tom: B
optic si
statistic
Mann-W
The
tion wi
clone m
the sou
activity
tation i
over w
tivity a
are con
This
region
and it i
the mi
ios pro
TR scedenote
d areas
evel ac-
ary of
rn and
to exhe baumber
own in
ws the
limate
ecome
in the
ranean
atitude
ope in
P. Lionello and F. Giorgi: Precipitation and cyclones
5
Fig. 7. Cyclone frequency change signal (considering only cyFig.
Cyclonedeeper
frequency
change
only
cyclone
clone7.minima
than 15
hPa).signal
Top: (considering
A2 minus CTR
scenario.
minima
than CTR
15hPa).
Top: A2
minusvalues
CTR scenario.
BotBottom: deeper
B2 minus
scenario.
Positive
denote higher
tom:
B2
minus
CTR
scenario.
Positive
values
denote
larger
frequency in climate scenarios. In the colored areas changes synare
optic
signal significant
in climate at
scenarios.
In the colored
changes
are
statistically
the 90% confidence
levelareas
according
to the
8 number
−2 month
statistically
significant
at the1090%
confidence
levelkm
according
to−1
the
Mann-Whitney
test. Units:
of
minima
.
Mann-Whitney test. Units: 10 number of minima km month .
two
regions
correlated with
synoptic
signalofinthe
a region
inThe
spatialis distribution
of the
correlation
precipitacluding
the
whole
Mediterranean
and
north
Africa
and
with
tion with the synoptic signal and with the frequency of cythe frequency
cyclone
coast of
clone
minima of
shows
that,centers
on onealong
hand,the
thenorthern
precipitation
at
the
Mediterranean
(Fig.
9).
Therefore,
the
comparison
bethe south-eastern coast of the basin is linked to the cyclonic
8 and
showsand,
the on
different
positions
of cyclone
tween Figs.
activity
inside
the 9basin,
another
hand, the
precipicenters
and
of
cyclone
activity
areas
that
produce
rainactivity
in the
tation in the northern part is linked to the cyclonic
northern
and
south-eastern
coasts
of
the
Mediterranean.
over western Europe. Therefore, the changes of cyclone acUsing
spatial distribution
for intertivity
andthe
of precipitation
shownof
bythe
thecorrelation
RegCM simulations
preting
the
climate
change
signal
shown
in
Figs.
5–7
brings
are consistent.
to This
the conclusion
that
the
reduction
of
cyclone
activity
and
analysis shows that the response of the Mediterranean
number
of
cyclones
inside
the
Mediterranean
region
(and
region to climate change is not necessarily homogeneous
mainly
its easternbypart)
is responsible
negative
and
it is in
conditioned
changes
of intensityfor
andtheposition
of
change
of
precipitation
in
its
eastern
part.
The
the mid-latitude storm track. Since future climatepositive
scenarios produce an intensification and a northward shift (away
www.adv-geosci.net/12/153/2007/
6
157
Fig. 8. Spearman Rank correlation of the seasonal precipitation
Fig. 8. Spearman Rank correlation of the seasonal precipitation
at the Croatian coast of the Adriatic Sea and over the continental
at the eastern Mediterranean coast and over the continental part of
part of Italy with the synoptic signal (top) and with the frequency of
Italy coast with the synoptic signal (top) and with the frequency of
cyclone centers deeper than 15 hPa (bottom). In the colored areas
cyclone centers deeper than 15hPa (bottom). In the colored areas
correlation is statistically significant at the 90% confidence level.
correlation is statistically significant at the 90% confidence level.
change in the northern part of the Mediterranean region is
instead caused by the increased strength of the mid-latitude
from
the Mediterraean) of the mid-latitude storm track this
storm track occurring mostly outside the region itself.
has contrasting effect in different areas within the Mediterranean. The increased intensity of the storm track prevails in
the
Mediterranean areas producing an increased winter
4 north
Conclusions
precipitation. The effect of its shift prevails in the southeastern
areas, of
forregional
which the
Mediterranean
is A2
a main
The analysis
climate
simulationsitself
of the
and
source
of moisture,
where
the reduced
activity
reB2 scenario
confirms
the global
MGMEcyclonic
results and
it shows
sults
in winter
a diminished
precipitation
at the coast
in future
wetter
conditions
at the northern
boundary
of clithe
mate
scenarios. region and drier along the southern and eastMediterranean
ern coast of the basin. A purpose of this paper is to explain such changes in the precipitation field (Fig. 5) on the
basis of changes in synoptic signal (Fig. 6) and cyclone freAcknowledgements.
Thethe
authors
thank Dr
X.Bi for fields
his help
with
quency (Fig. 7) using
respective
correlation
shown
the
and 9.
U.Boldrin for his contribution to the programs used
in graphics
Figs. 8 and
in this study.
Adv. Geosci., 12, 153–158, 2007
Fig. 9.
at the T
signal (t
15hPa (
nificant
Refere
Giorgi,
trend
I: Pre
2004
Giorgi,
trend
II: Fu
858,
Giorgi,
ranea
Jansà M
Carre
Part 2
Lionello
gion:
pitation
part of
ency of
d areas
evel.
k this
editerails in
winter
southmain
ty rere cli-
p with
ms used
158
Lionello P. and Giorgi F.: Precipitation and cyclones
P. Lionello and F. Giorgi: Precipitation and cyclones
This analysis shows that the response of the Mediterranean
region to climate change is not necessarily homogeneous
and it is conditioned by changes of intensity and position of
the mid-latitude storm track. Since future climate scenarios produce an intensification and a northward shift (away
from the Mediterraean) of the mid-latitude storm track this
has contrasting effect in different areas within the Mediterranean. The increased intensity of the storm track prevails in
the north Mediterranean areas producing an increased winter
precipitation. The effect of its shift prevails in the southeastern areas, for which the Mediterranean itself is a main
source of moisture, and where the reduced cyclonic activity
results in a diminished precipitation at the coast.
Acknowledgements. The authors thank X. Bi for his help with the
graphics and U. Boldrin for his contribution to the programs used
in this study.
Edited by: P. Alpert, H. Saaroni, and E. Heifetz
Reviewed by: two anonymous referees
References
Fig. 9. Spearman Rank correlation of the seasonal precipitation
Fig.
9. Turkish
Spearman
correlation
of thecoast
seasonal
at the
and Rank
Eastern
Mediterranean
with precipitation
the synoptic
atsignal
the Turkish
and
Eastern
Mediterranean
coastcenters
with the
synoptic
(top) and
with
the frequency
of cyclone
deeper
than
signal
(top)
and
with
the
frequency
of
cyclone
centers
deeper
15 hPa (bottom). In the colored areas correlation is statistically than
sig15hPa
(bottom).
In the
colored level.
areas correlation is statistically significant
at the 90%
confidence
nificant at the 90% confidence level.
The high resolution of the RegCM simulation allows the
identification of cyclones and the evaluation of the climate
change signal. Cyclone activity is projected to become
References
weaker over the eastern Mediterranean and stronger in the
north-western
In fact,
northinterannual
western Mediterranean
Giorgi,
F., Bi, X.areas.
and Pal,
J. S.:the
Mean,
variability and
is trends
partially
by the intensification
of the
in a affected
regional climate
change experiment
overmid-latitude
Europe. Part
I: Present day
climate
(1961-1990).
Dyn., 22,Europe
733–756
storm-track
which
occurs
over centralClim.
and western
in
2004a.
the
scenario simulations.
Giorgi,
Bi, X.distribution
and Pal, J.S.:
Mean,
interannual
and
The F.,
spatial
of the
correlation
of variability
the precipitatrends
a regional
climate
change
over Europe.
tion
within the
synoptic
signal
and experiment
with the frequency
of Part
cyII: Future climate scenarios (2071-2100). Clim. Dyn., 23, 839clone
minima shows that, on one hand, the precipitation at
858, 2004b.
the south-eastern coast of the basin is linked to the cyclonic
Giorgi, F., Lionello P.: Climate Change projections for the Mediteractivity
inside the basin, and, on another hand, the precipiranean region, Global Planet. Change, submitted, 2007
tation
in
northern
is linked
the cyclonic
activity
Jansà M.A.the
, Genovès
A., part
Picornell
M.A. ,to
Campins
J., Riosalido
R.,
over
western
Europe.
Therefore,
the
changes
of
cyclone
acCarretero O.: Western Mediterranean cyclones and heavy rain.
tivity
of precipitation
by the
RegCM
simulations
Part and
2: Statistical
approach,shown
Meteorol.
Appl.,
8, 43–56,
2001
are
consistent.
Lionello P., Dalan F., Elvini E. Cyclones in the Mediterranean Re-
Giorgi, F., Bi, X., and Pal, J. S.: Mean, interannual variability and
trends in a regional climate change experiment over Europe. Part
I: Present day climate (1961–1990), Clim. Dyn., 22, 733–756
2004a.
Giorgi, F., Bi, X., and Pal, J. S.: Mean, interannual variability and
trends in a regional climate change experiment over Europe. Part
II: Future climate scenarios (2071–2100), Clim. Dyn., 23, 839–
858, 2004b.
Giorgi, F. and Lionello P.: Climate Change projections for the
Mediterranean region, Global Planet. Change, accepted, 2007.
Jansà, M. A., Genovès, A., Picornell, M. A., Campins, J., Riosalido, R., and Carretero, O.: Western Mediterranean cyclones
and heavy rain. Part 2: Statistical approach, Meteorol. Appl., 8,
43–56, 2001.
Lionello, P., Dalan, F., and Elvini, E.: Cyclones in the Mediterranean Region: the present and the doubled CO2 climate scenarios, Clim. Res., 22, 147–159, 2002.
Lionello, P., Bhend, J., Buzzi, A., Della-Marta, P. M., Krichak, S.,
Jansá, A., Maheras, P., Sanna, A., Trigo, I. F., and Trigo, R.:
Cyclones in the Mediterranean region: climatology and effects
on the environment, in Mediterranean Climate Variability, edited
by: Lionello, P., Malanotte-Rizzoli, P., and Boscolo, R. Elsevier,
Amsterdam, The Netherlands, 324–372, 2006.
Lionello, P., Boldrin, U., and Giorgi, F.: Future changes in cyclone
climatology over Europe as inferred from a regional climate simulation, Clim. Dyn., doi:10.1007/s00382-007-0315-0, 2007.
New, M. G., Hulme, M., and Jones, P. D.: Representing twentieth century space time climate fields. Part II: Development of a
1901–1996 mean monthly terrestrial climatology, J. Climate, 13,
2217–2238, 2000.
Simmons, A. J. and Gibson, J. K.: The ERA-40 Project Plan, ERA40 Project Report Series n. 1, 2000.
gion: the present and the doubled CO2 climate scenarios. Clim.
Adv. Geosci., 12, 153–158, 2007
www.adv-geosci.net/12/153/2007/