NCAR CGD Seminar June 2015 Disruption of the European Climate Seasonal Clock in a warming world...
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Transcript of NCAR CGD Seminar June 2015 Disruption of the European Climate Seasonal Clock in a warming world...
NCAR CGD Seminar June 2015
Disruption of the European Climate Seasonal Clock in a warming world
Christophe Cassou (Cerfacs)Julien Cattiaux (Météo-France)
NCAR CGD Seminar June 2015
“Always blame global warming!” The polar vortex syndrome
NCAR CGD Seminar June 2015
Easy … but …
NCAR CGD Seminar June 2015
Temperature anomalies [5-12 Feb 2012]
“Always blame Blocking!”
850hPa wind anomaliesPressure anomalies
H
NCAR CGD Seminar June 2015
Temperature anomalies [20-25 July 2006]
“Always blame Blocking!”
H
850hPa wind anomaliesPressure anomalies
NCAR CGD Seminar June 2015
Temperature anomalies [20-25 July 2006]
“Always blame Blocking!”
H
Pressure anomalies
NCAR CGD Seminar June 2015
Pressure anomalies [20-25 July 2006]
H
“Always blame Blocking and global warming!”
NCAR CGD Seminar June 2015
The blocking syndrome
BLOCKIN
G
WILL
CAUSE
WARMER
SUMMERS
!
BLOCKIN
G
WILL
CAUSE
WARMER
SUMMERS
!
NCAR CGD Seminar June 2015
Communication is an art…
BLOCKING
BLOCKING
NCAR CGD Seminar June 2015
The seasonality of atm. circulation & Temp. over Europe
Temperature anomaliesPressure anomalies 850hPa wind anomalies
The 2012 European cold wave
The 2006 European heat wave
NCAR CGD Seminar June 2015
Evidence for strong seasonality in the atmos circulation temperature relationship.
1. Choice of the metric2. PDF Model
Climate Change effect
Summer starting datesAttribution simulation (CMIP5)Mordicus
Mechanims: snow and not land-sea contrast Work in observation today.
Winter: no change: aerosols, snow
Global warming, everywhere!
NCAR CGD Seminar June 2015Data: NCEP-NCAR reanalysis
DJF EOF modes of variability from winter days [1950-2012]
JJA EOF modes of variability from summer days [1950-2012]
Seasonality of the North Atlantic daily atm. circulation
NCAR CGD Seminar June 2015Data: NCEP-NCAR reanalysis
DJF EOF modes of variability from winter days [1950-2012]
JJA EOF modes of variability from summer days [1950-2012]
Seasonality of the North Atlantic daily atm. circulation
Northward migration of the centers of actionand modes of variability but for blocking
NCAR CGD Seminar June 2015Data: NCEP-NCAR reanalysis
DJF EOF modes of variability from winter days [1950-2012]
JJA EOF modes of variability from summer days [1950-2012]
Definition of a European circulation index
Northward migration of the centers of actionand modes of variability but for blocking
Definition of a annual daily box-average pressure index
NCAR CGD Seminar June 2015
Seasonal relationship between circulation and temp. (1)
Summer Surface temperature compositesWinter Surface temperature composites
Data: NCEP-NCAR reanalysis
NCAR CGD Seminar June 2015
Seasonal relationship between circulation and temp. (2)
Winter Surface temperature composites Summer Surface temperature composites
+ ECA dataset (dots)Data: NCEP-NCAR reanalysis
NCAR CGD Seminar June 2015
Definition of a western-Europe temperature index
Winter Surface temperature composites Summer Surface temperature composites
+ ECA dataset (dots)Data: NCEP-NCAR reanalysis
NCAR CGD Seminar June 2015
The seasonal clock of the European climate
Strength of the regressionbetween PSL index &
2m-TEMP index
0.33 oC/hPa
0.66 oC/hPa
1oC/hPa
Neg. Reg/Corr. Pos. Reg/Corr.
NCAR CGD Seminar June 2015
The seasonal clock of the European climate
Neg. Reg/Corr. Pos. Reg/Corr.
NCAR CGD Seminar June 2015
Neg. Reg/Corr. Pos. Reg/Corr.
The seasonal clock of the European climate
NCAR CGD Seminar June 2015
Neg. Reg/Corr. Pos. Reg/Corr.
Uncertainties for the seasonal clock (NCEP)
NCEP PSL / 2mT ECA
NCEP PSL / 2mT NCEP
NCAR CGD Seminar June 2015
Neg. Reg/Corr. Pos. Reg/Corr.
x 20CR PSL / 2mT 20CRNCEP PSL / 2mT ECA
NCEP PSL / 2mT NCEP
Uncertainties for the seasonal clock (20CR)
NCAR CGD Seminar June 2015
BLOCKING, everywhere!
Bilan ici et ojectives
ModelesMettre quelque part le nombre de jours traites.
NCAR CGD Seminar June 2015
Evaluation of the CNRM-CM5 model
NCEP + ECA observational datasets (1950-2010)
CNRM-CM5 historical simulation (1950-2010)
NCAR CGD Seminar June 2015
Obs. envelopHIST. envelop
The CNRM-CM5 model reproduces very well the European seasonal clock.
Neg. Reg/Corr.
The CNRM-CM5 seasonal clock
There is a slight underestimation of the PSL/TAS relationship for summer months (July and May)
NCAR CGD Seminar June 2015
Seasonal clock in [2070-2100] in RCP85
PiControl [1000 years] PiControl [1000 years]
1. Considerable reduction of the PSL/TAS relation in late winter/early spring
2. Clear increase of of the PSL/TAS relation in summer
3. No significant change in PSL/TAS relation in fall
NCAR CGD Seminar June 2015
Winter changes
PDF for PSL Winter days (PiControl)
PD
F f
or
Tem
p.
Win
ter
days
(PiC
ontr
ol)
NCAR CGD Seminar June 2015
Winter changes
PDF for PSL Winter days (PiControl)
(RCP85)
PD
F f
or
Tem
p.
Win
ter
days
(PiC
ontr
ol)
(RC
P8
5)
NCAR CGD Seminar June 2015
(Mean c
orr
ect
ed R
CP8
5)
(Mean corrected RCP85)
Winter changesPDF for PSL Winter days (PiControl)
PD
F f
or
Tem
p.
Win
ter
days
(PiC
ontr
ol)
Cold extremes warm more than the meanMild extremes warm less the mean
Conditional change of 2m-Temperature reduction of variance
Zonal flows are less efficient to bring heat inland Blocking flows are less efficient to bring cold westward
NCAR CGD Seminar June 2015
Summer changes
NCAR CGD Seminar June 2015
Summer changes
Loss of PSL/Temp relationship in winter due to reduced conditional variance of Temperature
Increase of PSL/Temp relationship in summer due to increase variance of Temperature (less dependant on atm. circulation)
NCAR CGD Seminar June 2015
Change in zonal gradients
2070-2100 East-West Contrast (EWC) of January = EWC in March of 1970-2000 ---> Two month seasonal advance
Maximum change in summer for land sea contrast
---> One month seasonal advance
NCAR CGD Seminar June 2015
BLOCKING, everywhere!
Bilan des mecanismes des changementsde variance.
Annonce de la summer date (humour sur la recherchede la non-significativite).
Mettre mot detectableDefinition de la metrique. Mettre aussi une balance avec radiatifet advection
NCAR CGD Seminar June 2015
The summer starting date is defined as the day where the correlation between PSL and West Temp. indices crosses 0
The winter starting date is defined as the day where the correlation between PSL and West Temp. indices crosses 0
31st of March [1980-2010]
The summer starting date
NCEP20CR PiCtl
12 April
10-member Historical
NCAR CGD Seminar June 2015
The summer starting date is defined as the day where the correlation between PSL and West Temp. indices crosses 0
The winter starting date is defined as the day where the correlation between PSL and West Temp. indices crosses 0
The summer starting date (historical period)
NCEP20CR PiCtl
10-member Historical
Earlier onset of summer by ~10 days between the 1950’s and the 1990’s (~2.5 days/decade trend)
On the verge of detectability for this metric in presence of strong interannual variability
NCAR CGD Seminar June 2015
The summer starting date (the XXIst century under RCP85)
NCEP20CR PiCtl
10-member Historical
Earlier onset of summer by ~10 days between the 1950’s and the 1990’s (~2.5 days/decade trend)
On the verge of detectability for this metric in presence of strong interannual variability
Additional ~15 day winter shortening by [2070-2100]
The sharpest trend is now!
NCAR CGD Seminar June 2015
Ensemble Means
Detection and attribution
PiCtl
No volcanic eruption [1920-1960]
The observed current winter shortening is attributable to GHG forcing …
… But modulated by aerosols forcings
NCAR CGD Seminar June 2015
Detection and attribution
Agreement between observed very late summer onset in the 1950-1960 and HISTANT simulations. Luck? Sampling? True?
Origin of the observed earlier summer onset at the beginning of the 20th century. Quality of the data? Atlantic Multidecadal Variability (AMV) influences?
NCAR CGD Seminar June 2015
Dedicated simulations : the MORDICUS project
Definition of the SPEEDY-attribution runs for processed-oriented approach 1850-1990 anthropogenic aerosols trends contracted in 30
years --> 12 members of 30yr starting from PiControl
Doubling CO2 in 30 years --> 12 members of 30yr starting from PiControl
Confirmation of the aerosol forcing on the summer starting date (delay by X days)
Confirmation of the GHG forcing on the summer starting date (advance by X days)
AMO influences: --> 12 members of 30yr AMO+ and 12 members of 30yr AMO- starting from PiControl
AMO+
AMO-
No significant impact of AMO phases in CNRM-CM5
NCAR CGD Seminar June 2015
Mechanisms : land-sea contrast versus East-West gradient
Change in March Land-Sea contrast is NOT responsible for the ongoing trend
Reduction in Eastern-Western Europe temp. gradient in March is responsible for the ongoing earlier summer: role of Eastern Europe Snow decline
Snow cover (Eastern Europe)
Land-Sea contrast
NCAR CGD Seminar June 2015
Comparison between observed and model trends for snow cover
Snow cover (Eastern Europe)
Reduction in Eastern-Western Europe temp. gradient in March is responsible for the ongoing earlier summer: role of Eastern Europe Snow decline
NCAR CGD Seminar June 2015
Can we find year-to-come analogs today?199
6200
6201
3
1990
2007
2014
NCAR CGD Seminar June 2015
Can we find year-to-come analog today? ---> YES!
1996
2006
2013
1990
2007
2014
Snow years
Snow-free years
upper-tercile
NCAR CGD Seminar June 2015
BLOCKING, everywhere!
Mettre ici les cartes des z500 et les cartes de neigede Fev? De Mars?
Annonce de la summer date (humour sur la recherchede la non-significativite).
Mettre le nombre dejours.Mettre graphe Yohan in caseof question MORDICUS.
Vanter les merrites de la metrique: integral
NCAR CGD Seminar June 2015
The winter starting date (the XXIst century under RCP85)
NCEP20CR PiCtl
10-member Historical
No clear signal for winter starting dates
NCAR CGD Seminar June 2015
Detection and attribution (winter)
PiCtl
No volcanic eruption [1920-1960]
GHG forcing leads to later winter onset …
… but strongly counteracted by anthropogenic aerosols forcing
Ensemble Means
NCAR CGD Seminar June 2015
PiCtl
Confirmation of weak GHG forcing for later winter onset from MORDICUS experiments…
Confirmation of strong aerosols forcing for earlier winter onset from MORDICUS project
Ensemble Means
Dedicated simulations : the MORDICUS project
NCAR CGD Seminar June 2015
Thanks for your attention