J. Ignacio López-Moreno: Effects of NAO on combined temperature and precipitation winter modes snow...

Effects of NAO on combined temperature and precipitation winter modes and snow cover in Mediterranean mountains: observed relationships and projections for the 21st century

J. Ignacio Ló[email protected]

IMPACT OF NAO ON WINTER TEMPERATURE AND PRECIPITATION MODES AND SNOW COVER IN THE MEDITERRANEAN MOUNTAINS

- Plant and animal phenology-Tourism- Natural hazards: avalanches and floods- Water resources

SNOW IN THE MEDITERRANEAN MOUNTAINS

Alps and ApeninesIberian peninsula

Atlas

Turkey

Carphatians Lebanon

CORRELATION OF NAOi WITH WINTER (DJFM) PRECIPITATION AND TEMPERATURE: 1950-2005

Precipitation

Temperature

Correlation significantat 95%

Objectives

1- To assess the effect of NAO on combined precipitation and temperature and snow accumulation in the Mediterranean mountains.2- To assess the capability of GCMs for reproducing the observed relationships.3- To check if simulated relationships will remain stationary or will change in the next century due to increasing GHGs concentrations.

Problem: In general snow data is scarce and not available for researchers in most of the Mediterranean region.

Winter modes approach

1- Warm and wet (WW): Tª>60th percentile; Precip>60th percentile2- Warm and dry (WD): Tª>60th percentile; Precip<40th percentile3- Cold and wet (CW): Tª<40th percentile; Precip>60th percentile4- Cold and dry (CD): Tª<40th percentile; Precip<40th percentile

DJF

M m

ean

sn

ow

acc

um

ula

tion

(p

erc

en

tile

s)

0.0

0.2

0.4

0.6

0.8

1.0

WW WD CW CD WW WD CW CD WW WD CW CD WW WD CW CD

Château d’Oex, 980 m a.s.l.

Davos, 980 m a.s.l.

Arosa, 1850m a.s.l.

Saentis, 2500 m a.s.l.

Winter modes approach

1- Warm and wet (WW): Tª>60th percentile; Precip>60th percentile2- Warm and dry (WD): Tª>60th percentile; Precip<40th percentile3- Cold and wet (CW): Tª<40th percentile; Precip>60th percentile4- Cold and dry (CD): Tª<40th percentile; Precip<40th percentile

DJF

M m

ean

sn

ow

acc

um

ula

tion

(p

erc

en

tile

s)

0.0

0.2

0.4

0.6

0.8

1.0



Davos, 980 m a.s.l.

Arosa, 1850m a.s.l.


Day

0 50 100 150 200 250

Sn

ow

de

pth

0

20

40

60

80

100


Day

0 50 100 150 200 250

Sn

ow

de

pth

0

200

400

600

Warm/Wet

Warm/Dry

Cold/WetCold/Dry


Study area and case studies

1

2

3

4

5

6

7

8

9

10

11

12

13

1- Cantabrian M. (7) 5- Atlas (84) 9- Dinaric Alps (18) 13- N. Turkey (181)2- Central S. (10) 6- Alps (113) 10- Pindos (23) 14- Caucasus (85)3- Pyrenees (22) 7- Apenines (16) 11- Balkan M. (16) 15- Lebanon M. (8)4- S.Nevada (4) 8- Carpathians (16) 12- Taurus (87)

14

15

Data: CRU TS2.1 (50km grid size). Study period: 1950-2005

1

4

Iberian Peninsula: Pyrenees

López-Moreno and Vicente-Serrano (2007). Atmospheric circulation influence on the interannual variability of snow pack in the Spanish Pyrenees during the second half of the 20th century. Nordic hydrology 38 (1):38-44.

3

Iberian Peninsula: Pyrenees 3

Teleconnection index

Component 1Snow

accumulation

NAO *-0.38 *-0.39

EA -0.17 0.06

EA/WR -0.24 -0.04

SCA 0.19 0.26

* α <0.05

López-Moreno and Vicente-Serrano (2007). Atmospheric circulation influence on the interannual variability of snow pack in the Spanish Pyrenees during the second half of the 20th century. Nordic hydrology 38 (1):38-44.

Iberian Peninsula: Pyrenees 3

García et al. (2009) Major avalanches occurrence at regional scale and related atmospheric circulation patterns in the Eastern Pyrenees. Cold Regions Science and Technology 59 (2009) 106–118

173 of 241 major avalanche events in the Pyrenees have been observed during winters dominated by negative NAOi

Iberian Peninsula 1- Cantabrian M. 2- Central S. 3- Pyrenees4- S.Nevada

2

3

4

Coe

ffic

ien

t of

corr

elat

ion

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0Cantabrian mountains Central System Pyrenees Sierra Nevada

Prec.Tmx Tmn Tavg Prec.Tmx Tmn Tavg Prec.Tmx Tmn Tavg Prec.Tmx Tmn Tavg

Correlation between winter NAOi(DJFM) and winter precipitation and temperature

Tmn Tavg PrecipTmx Tmn Tavg PrecipTmx Tmn Tavg PrecipTmx Tmn Tavg PrecipTmx

Iberian Peninsula 1- Cantabrian M. 2- Central S. 3- Pyrenees4- S.Nevada

2

3

4

Winter NAOi(DJFM) under different combinations of precipitation and temperature

Central System

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Tem

pera

ture

0.0

0.2

0.4

0.6

0.8

1.0

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Cantabrian M. Central S. Pyrenees S. Nevada

NA

O (

DJF

M)

-3

-2

-1

0

1

2

3Cantabrian mountains Central System Pyrenees Sierra Nevada


-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

NAO

WWWD

CWCD

Morocco: Atlas

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Tem

pera

ture

0.0

0.2

0.4

0.6

0.8

1.0

Atlas

Co

effic

ien

t of c

orr

ela

tion

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0Atlas

Prec.Tmx Tmn Tavg

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

NAO

NA

O (

DJF

M)

-3

-2

-1

0

1

2

3

WW WD CW CD

Atlas

Tmn Tavg PrecipTmx

Alps

WW WD CW CD

Y D

ata

-3

-2

-1

0

1

2

3Alps

NA

O (

DJF

M)

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Tem

pera

ture

0.0

0.2

0.4

0.6

0.8

1.0

Alps

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

NAO

Co

effi

cien

t of

co

rrel

atio

n

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0Alps

Prec.Tmx Tmn Tavg

Tmn Tavg PrecipTmx

Apenines

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

NAO

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Tem

pera

ture

0.0

0.2

0.4

0.6

0.8

1.0

Apenines

Coe

ffici

ent o

f cor

rela

tion

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0Apenines

Prec.Tmx Tmn Tavg

NA

O (

DJF

M)

-3

-2

-1

0

1

2

3Apenines

WW WD CW CD

Tmn Tavg PrecipTmx

BalkansCarphatianDynaric AlpsPindos

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

NAO

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Tem

pera

ture

0.0

0.2

0.4

0.6

0.8

1.0

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Precipitation0.0 0.2 0.4 0.6 0.8 1.0

Dynaric Alps Pyndos Balkan M. Carpathian

NA

O (

DJF

M)

-3

-2

-1

0

1

2

3CarpathianDynaric Alps Pyndos Balkan M.


Prec.Tmx Tmn Tavg

Coe

ffic

ien

t of

co

rrel

atio

n

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0CarpathianDynaric Alps Pindos Balkan M.

Prec.Tmx Tmn TavgPrec.Tmx Tmn Tavg Prec.Tmx Tmn TavgTmn TavgPrecipTmx Tmn TavgPrecipTmx Tmn TavgPrecipTmx Tmn TavgPrecipTmx

NA

O (

DJF

M)

-3

-2

-1

0

1

2

3Taurus N. Turkey Caucasus Lebanon

WW WD CW CD WW WD CW CD WW WD CW CDWW WD CW CD

TaurusN. TurkeyCaucasusLebanon

-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0

NAO

Coe

ffici

ent o

f cor

rela

tion

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

0.4

0.6

0.8

1.0Taurus N. Turkey Caucasus Lebanon

Prec.Tmx Tmn Tavg Prec.Tmx Tmn Tavg Prec.Tmx Tmn Tavg Prec.Tmx Tmn TavgTmn TavgPrecipTmx Tmn TavgPrecipTmx Tmn TavgPrecipTmx Tmn TavgPrecipTmx

ANOVA TEST

X diference is significant at α<0.05

WW WD CWWD CW CD CW CD CD

Cantabrian M. X O O X O O

Central S. X O O X O O

Pyrenees X O O X X X

S. Nevada X O X X O X

Atlas O O X O O X

Alpes O O O X X O

Apenines O O O O O X

Carpathian M. X O O O O O

Dynaric Alps X O O X O O

Pindos X O X O O X

Balkans O O O O O X

Taurus O O X O O O

N. Turkey O O O O X O

Caucasus O O O O O O

Lebanon O O O O O O

What do the models inform for the next century?

Simulated temperature and precipitation simulated for each mountain system, and NAOi for the period 1900 and 2099 by 10 different GCMs were used to:

-Asses the capability of GCMs to reproduce the observed relationship between precipitation and temperature and NAOi across the Mediterranean area

-Assess if relationships between NAO and winter modes observed in the last century are expected to continue during the 21st century SRES A1B

Distribution of observed (OBS) and simulated winter NAO values for the 20th (C) and 21st (F) centuries

NA

O v

alu

es

-2.0

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

2.0

MRI MPI MIUB MIROC GFDL CSIRO CNRM CCMA BCM UKMOOBS

C F C F C F C F C F C F C F C F C F C F

Simulated correlation between NAOi and precipitation for the control period (1950-2006)

Simulated correlation between NAOi and precipitation for the control period (1950-2006) and 21st century (2000-2099)

Simulated correlation between NAOi and temperature for the control period (1950-2006) and 21st century (2000-2099)

WW WW_F WD WD_F CW CW_F CD CD_F

Lebanon

Mea

n N

AO

i (D

JFM

)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Pyrenees Alps

WW WW_F WD WD_F CW CW_F CD CD_F

Mea

n N

AO

i (D

JFM

)

-1.5

-1.0

-0.5

0.0

0.5

1.0

1.5

Pindos

WW WD CW CD

WW WD CW CD WW WD CW CD

WW WD CW CD

C F C F C F C F C F C F C F C F

C FC FC FC FC FC FC FC F

Average NAOi for different winter modes during the control period (C, 1950-2006) and the 21st century (F. 2000-2099)

MRIMPIMIUBMIROCGFDLCSIROCNRMCCMABCMUKMO

ObservedModel average

Number of GCMs which show significant differences in NAOi according to different winter modes during the control period (1950-2006) and 21st century (2000-2099)

ANOVA TEST


Cantabrian M. 4 0 3 6 1 1Central S. 6 0 5 6 0 4Pyrenees 6 0 1 7 4 4S. Nevada 5 0 7 5 2 5Atlas 2 3 9 0 3 3Alpes 1 1 0 6 5 1Apenines 2 1 4 4 0 1Carpathian M. 5 1 0 2 1 0Dynaric Alps 6 2 0 1 0 1Pindos 5 1 6 0 1 2Balkans 0 1 4 0 1 1Taurus 0 1 2 1 2 1N. Turkey 0 1 1 0 1 2Caucasus 0 2 1 0 0 0Lebanon 0 2 2 1 2 0


Cantabrian M. 8 2 2 8 3 3Central S. 8 1 7 9 2 7Pyrenees 9 2 3 10 2 7S. Nevada 8 0 8 8 1 9Atlas 5 2 8 3 2 7Alpes 7 1 3 8 7 4Apenines 7 1 2 7 3 4Carpathian M. 8 3 2 9 3 4Dynaric Alps 9 0 4 6 1 6Pindos 8 0 8 3 3 3Balkans 2 1 4 2 3 4Taurus 0 2 5 1 4 2N. Turkey 0 1 2 1 1 0Caucasus 1 2 4 1 1 0Lebanon 0 3 5 0 3 2

1950-2006

2000-2099

Change in temperature and precipitation simulated by 10 GCMs

Cha

nge

in t

empe

ratu

re (

ºC)

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Ch

ang

e in

pre

cipi

tatio

n (%

)

-40

-30

-20

-10

0

10

20

30

40

Cant.M.S.Cent. Pyr. S.Nev Atlas Alps Apen. Carp. Dyn.A.Pynd. Balk. Taur. N.Turk.Cauc. Leb

2000-2099 period compared to 1950-2000

Temperature

Precipitation



Change in the number of winters belonging to different winter modes during the 21st using the percentiles of the period 2000-2099 (C) and 1950-2000 (F)

Cant.M.S.Cent. Pyr. S.Nev Atlas Alps Apen. Carp. Dyn.A.Pynd. Balk. Taur. N.Turk.Cauc. Leb

Num

ber

of w

inte

rs

0

5

10

15

20

25

30

Num

ber

of w

inte

rs

0

5

10

15

20

25

30

35

Cold and wet

Cold and dry

C F C F C F C F C F C F C F C F C F C F C F C F C F C F C F




Nu

mb

er

of

win

ters

0

20

40

60

80

100Warm and wet

Nu

mb

er

of

win

ters

0

20

40

60

80

100Warm and dry



Cant.M.S.Cent.Pyr. S.Nev Atlas Alps Apen. Carp.Dyn.A.Pynd. Balk. Taur. N.Turk.Cauc. Leb

Change in the number of winters belonging to different winter modes during the 21st using the percentiles of the period 2000-2099 (C) and 1950-2000 (F)



Conclusions

NAO exerts a strong influence on the occurrence of different winter modes across the mediterranean area

- In the Iberian Peninsula, Atlas, Balkans and Greece it mainly causes differences between wet and dry modes.- In the Alps, Taurus and Lebanon NAO introduce significant differences between cold and warm modes

The occurrence of winter modes has a major influence on the accumulation of snow in the mountain areas. Hence, NAO pattern is an important driver of the interannual variability of snowpack.

NAO (DJFM)-2 -1 0 1 2

Sno

w d

epth

(-)

-4

-2

0

2

4

A

Snow

dep

th (

-)

-3-2-10123

NA

O (

DJF

M)

-3-2-10123

B

r= - 0.59p< 0.05

Values above de average Values below the average

Pe

ars

on´s

co

rre

latio

n c

oe

ffic

ient

-1.0

-0.8

-0.6

-0.4

-0.2

0.0

0.2

All snow poles Snow polesbelow 2100 m

Snow polesabove 2100 m

Number of cases: 86

Number of cases: 62

Number of cases: 24

µ = -0.36

µ = -0.48

Conclusions

GCMs have shown a reasonable skill for reproducing NAO variability, most of simulations project an increase in NAO for the next decades

GCMs reproduce adequately the observed correlations between NAO and precipitation across the basin, and they have a lower capability for reproducing correlations with temperature. In general, the influence of NAO in the ocurrence of contrasted winter modes is well simulated. Such influence tends to be maintained, even strengthed in the next decades.

These results suggest that the projected upward trend of NAO in the next decades may lead to higher frequency of winter modes unfavourable for snowpack development

An expected increase of temperature (1.5-2ºC) will cause that the number of cold (warm) winters as observed during the 1950-2000 period will decrease (increase) dramatically in the 21st century.

Conclusions

Thanks!

J. Ignacio López-Moreno: Effects of NAO on combined temperature and precipitation winter modes snow...

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