19 October 2005The CRCES Workshop on Decadal Climate Variability Modelling the Variability of...
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Transcript of 19 October 2005The CRCES Workshop on Decadal Climate Variability Modelling the Variability of...
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Modelling the Variability of Midlatitude Storm Activity on
Decadal to Century Time Scales
Hans von Storch, Institute for Coastal Research, GKSSIrene Fischer-Bruns, Max Planck Institute for MeteorologyGermany
19 October 2005 The CRCES Workshop on Decadal Climate Variability
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)
Model & Experiments
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 1000 years
(present day conditions)
19 October 2005 The CRCES Workshop on Decadal Climate Variability
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 low-frequency 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
1675-1710vs. 1550-1800
Reconstruction from historical evidence, from Luterbacher et al.
Late Maunder Minimum
Model-based reconstuction
19 October 2005 The CRCES Workshop on Decadal Climate Variability
IPCC SRES A2 and B2 emissions marker scenarios
• A2Business as usual
External Forcing – Future Scenarios
• 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( 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)
• Low frequency variability in temperature modes and Extratropical storminess(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, L08707Fischer-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
12 hourly pressure changes exceeding 16 hPa / 12hLund
Stock-holm
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.)
19 October 2005 The CRCES Workshop on Decadal Climate Variability
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)
Model & Experiments
1 Historical Simulation 1550-19901550-1990(time dependent forcing)(time dependent forcing)
3 Future Climate Change Simulations3 Future Climate Change Simulations (CMIP2, (CMIP2, SRES A2/B2) (152 resp. 110 years)/B2) (152 resp. 110 years)
Control Simulation Control Simulation 1000 years1000 years
(present day conditions)(present day conditions)
19 October 2005 The CRCES Workshop on Decadal Climate Variability
• 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
Simulated data10m maximum wind speed
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Analysis of different model experiments with respect to gale frequency
Determination of simple indicators describing storm activity
Model Study
Storm IntensityIndex
Storm Shift Index
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 pre-industrial 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 last 300 years of the control run of 1000 years length.
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) in the A2 climate change experiment.
19 October 2005 The CRCES Workshop on Decadal Climate Variability
industrial – pre-industrial
Storm Intensity
DJF
JJA
A2 – pre-industrial
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Storm Intensity Mean number of gale-days averaged over time and region
NH: no changeSH: increase
pre-ind ind A2
Storm Intensity Index
Storm intensity index
= plain storm count
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Storm Intensity Mean number of galedays averaged over time and region
NH: no changeSH: increase
pre-ind ind A2
N Atl: increase N Pac: decreaseStorm Intensity
Index
pre-ind ind A2
(150E-90W)
(90W-30E)
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Storm Shift
26.5 %
23.4 % NAtl (DJF)
NPac(DJF)
SH(JJA)
11.2 %
Leading EOFs pre-ind Pattern of slope
coefficient in A2
y = -0.18.x + 34.1 -53%
y = 0.20x+20.7 +95%
y = 0.22x + 26.5 + 84%
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Storm Shift
PCs obtained by projection onto EOFEOFs pre-ind
NAtl (DJF)
NPac(DJF)
Storm Shift Index
SH(JJA)
pc1
pc4
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Poleward shift (NE)Intensity: slight increase
Poleward shiftIntensity: decrease
(11-yr running mean)
Temp & Indices:No correlation in pre-industrial period
N Atlantic
Warming and Storms
pc1 pc4
N Atlantic
N Pacific
Warming and Storms
NAtl TempStorm Intensity IndexStorm Shift Indices
NPacTempStorm Intensity IndexStorm Shift Index
19 October 2005 The CRCES Workshop on Decadal Climate Variability
Intensity: sharp increasePoleward shift
Warming and Storms
Southern Hemisphere
SH TempStorm Intensity IndexStorm Shift Index
(11-yr running mean)
19 October 2005 The CRCES Workshop on Decadal Climate Variability
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.
Hans von
Storch
19 October 2005 The CRCES Workshop on Decadal Climate Variability
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 pre-industrial 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
Irene Fischer-
Bruns