Download The CRCES Workshop on Decadal Climate

Hans von Storch, Institute for Coastal Research, GKSS
Irene Fischer-Bruns, Max Planck Institute for Meteorology
Germany
Modelling the Variability of
Midlatitude Storm Activity on Decadal
to Century Time Scales
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Model & Experiments
Atmosphere-Ocean GCM ECHO-G
Atmospheric Model ECHAM4 (T30)
(~3.75°x 3.75°  ~300 km x 300 km)
Ocean Model HOPE-G (T43)
(~2.8°x 2.8°  ~200 km x 200 km)
2 Historical Simulations
1550-1990
(time dependent solar / volcanic / GHG forcing)
3 Future Climate Change Simulations
(CMIP2, SRES A2/B2)
(152 resp. 110 years)
Control Simulation
(present day conditions)
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
1000 years
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
The millennial run
generates temperature
variations considerably
larger than MBH-type
reconstructions.
The simulated
temperature variations
are of a similar range
as derived from NH
summer dendro-data,
from terrestrial
boreholes and lowfrequency proxy data.
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Reconstructed and simulated winter temperature
anomalies in eastern China (Liu et al., 2005)
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Reconstruction from historical
evidence, from Luterbacher et al.
Late Maunder
Minimum
Model-based reconstuction
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
1675-1710
vs. 1550-1800
External Forcing – Future
IPCC SRES A2Scenarios
and B2 emissions marker scenarios
• A2
Business as usual
• B2
Strong focus on
environmental protection
Lower emissions –
less future warming
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Applications so far
•
Methodical analysis of performance of MBH method and MM05 “AHS” mechanism.
(von Storch, H., E. Zorita, J. Jones, Y. Dimitriev, F. González-Rouco, and S. Tett, 2004:
Reconstructing past climate from noisy data, Science 306, 679-682;
von Storch, H., and E. Zorita, 2005: Comment to "Hockey sticks, principal components and
spurious significance" by S. McIntyre and R. McKitrick, Geophys. Res. Lett. (in press)
doi:10.1029/2005GL022753)
•
Simulation of Late Maunder Minimum – regional European or near-global
phenomenon
(Zorita, E., H. von Storch, F. González-Rouco, U. Cubasch, J. Luterbacher, S. Legutke, I.
Fischer-Bruns and U. Schlese, 2004: Climate evolution in the last five centuries simulated
by an atmosphere-ocean model: global temperatures, the North Atlantic Oscillation and the
Late Maunder Minimum. Meteor. Z. 13, 271-289)
•
Comparison with multidecennial Chinese temperatures
•
Low frequency variability in temperature modes and Extratropical storminess
(刘 健 , H. von Storch, 陈 星, E. Zorita, 郑景云, and 王苏民, 2005: 千年气候模拟与中国东部温度重
建序列的比较研究 (Comparison of simulated and reconstructed temperature in eastern China
during the last 1000 years), Chinese Science Bulletin, in press)
(Zorita, E., F. González-Rouco, H. von Storch, J.P. Montavez und F. Valero, 2005: Natural
and anthropogenic modes of surface temperature variations in the last millennium,
Geophys. Res. Letters 32, L08707
Fischer-Bruns, I., H. von Storch, F. González-Rouco and E. Zorita, 2005: Modelling the
variability of midlatitude storm activity on decadal to century time scales. Clim. Dyn. DOI
10.1007/s00382-005-0036-1)
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
North Atlantic Storminess: Observational results
Worsening of storminess in NAtl since a minimum in
the 1960s consistent with NAO changes
No significant changes over last 100 years
(WASA, 1998)
Different storm indicators from pressure readings
1780/1820-2000
 No evidence of long-term trend
(Bärring & von Storch, GRL, 2005.)
Lund
12 hourly pressure changes exceeding 16 hPa / 12h
Stockholm
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Model & Experiments
Atmosphere-Ocean GCM ECHO-G
Atmospheric Model ECHAM4 (T30)
(~3.75°x 3.75°  ~300 km x 300 km)
Ocean Model HOPE-G (T43)
(~2.8°x 2.8°  ~200 km x 200 km)
1 Historical Simulation
1550-1990
(time dependent forcing)
3 Future Climate Change Simulations
(CMIP2, SRES A2/B2)
(152 resp. 110 years)
Control Simulation
(present day conditions)
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
1000 years
Simulated data
10m maximum wind speed
• diagnosed at every grid-point and at every time step
• stored every 30 minutes
• output every 12 hours
Extreme wind speed events per season
( 8 Bft, gales )
were counted
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Model Study
Analysis of different model experiments
with respect to gale frequency
Determination of simple indicators
describing storm activity
Storm Intensity
Index
19 October 2005
Storm Shift
Index
The CRCES Workshop on Decadal
Climate Variability
Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern
winter season DJF (left) and in the southern winter season JJA (right) for the preindustrial period 1551-1850 in the historical experiment (upper panels) and mean
number of storm days (10m wind speed reaching at least 10 Bft, lower panels).
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern
winter season DJF (left) and in the southern winter season JJA (right) for the
industrially influenced period 1851-1990 in the historical experiment.
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern
winter season DJF (left) and in the southern winter season JJA (right) during the
19 October 2005
The CRCES Workshop on Decadal
last 300 years of the control run of
1000
years length.
Climate
Variability
Mean number of gale days (10m wind speed reaching at least 8 Bft) in the northern
winter season DJF (left) and in the southern winter season JJA (right) in the A2
climate change experiment.
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Storm Intensity
A2 –
pre-industrial
industrial –
pre-industrial
DJF
JJA
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Storm Intensity
Mean number of gale-days
averaged over time and region
Storm intensity
index
pre-ind
ind
NH: no change
SH: increase
19 October 2005
A2
= plain storm
count
Storm Intensity
Index
The CRCES
Workshop on Decadal
Climate Variability
Storm Intensity
pre-ind
ind
Mean number of galedays
averaged over time and region
pre-ind
A2
ind
(90W-30E)
(150E-90W)
NH: no change
SH: increase
19 October 2005
Storm Intensity
Index
The CRCES
Workshop on Decadal
Climate Variability
N Atl: increase
N Pac: decrease
A2
Storm Shift
NAtl
(DJF)
23.4 %
y = 0.20x+20.7
NPac
(DJF)
+95%
26.5 %
y = -0.18.x + 34.1 -53%
SH
(JJA)
11.2 %
y = 0.22x + 26.5 + 84%
19 October 2005
Leading EOFs pre-ind
Pattern of slope
coefficient in A2
The CRCES Workshop on Decadal
Climate Variability
Storm Shift
Storm Shift
Index
pc1
pc4
NAtl
(DJF)
NPac
(DJF)
SH
(JJA)
19 October 2005
EOFs pre-ind
The CRCES Workshop on Decadal
Climate Variability
PCs obtained by projection onto EOF
Warming
Storms
N Atlantic andNAtl
Temp
N Atlantic
pc1
Storm Intensity Index
Storm Shift Indices
pc4
N Pacific
Warming and Storms
Poleward shift (NE)
Intensity: slight increase
NPacTemp
Storm Intensity Index
Storm Shift Index
Temp & Indices:
No correlation in
pre-industrial period
Poleward shift
Intensity: decrease
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
(11-yr running mean)
Warming and Storms
Southern
Hemisphere
SH Temp
Storm Intensity Index
Storm Shift Index
Intensity: sharp increase
Poleward shift
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
(11-yr running mean)
Conclusions – long term simulation
• Historical runs done.
• Realistic sequence of warming and
cooling.
• Variations larger than in multi-proxy
regression-type reconstructions, but
consistent with other reconstructions and
some regional data.
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Hans
von
Storch
Conclusions - storms
• Analysis of long-term model data with respect to wind speed
extremes; Determination of two simple indicators describing
storm intensity and storm track location.
• The storm indices show no trends in the historical experiments,
except for SH in 20th century.
• NH Temperature and Storm activity are uncorrelated in the preindustrial period
• Future climate change scenario A2:
- Parallel increase of storminess indices and temperatures.
- Poleward shift of the region with maximum gale intensity for
NAtlantic (NE), NPacific and SH; Storm intensity is
constant over the NH as a whole, but increasing in
the Atlantic region and decreasing in the Pacific
- Increase of storm intensity for SH
19 October 2005
The CRCES Workshop on Decadal
Climate Variability
Irene
FischerBruns