rcm climate change projection uncertainty
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RCM Climate Change Projection Uncertainty. Xin-Zhong Liang Department of Atmosphere & Ocean Science Earth System Science Interdisciplinary Center University of Maryland, College Park. 2013 August 13 NCPP Quantitative Evaluation of Downscaling Workshop. - PowerPoint PPT PresentationTRANSCRIPT
RCM Climate Change Projection Uncertainty
Xin-Zhong LiangDepartment of Atmosphere & Ocean ScienceEarth System Science Interdisciplinary CenterUniversity of Maryland, College Park
2013 August 13
NCPP Quantitative Evaluation of Downscaling Workshop
Only MRI with a medium resolution captures the observed NAM rainfall annual cycle. CCSM3 with higher resolution and updated physics reduces PCM amplitude error by half. MIROC3 finer resolution improves the phase but worsens the magnitude .
Liang, X.-Z., J. Zhu, K.E. Kunkel, M. Ting, and J.X.L. Wang, 2008: Do CGCMs simulate the North American monsoon precipitation seasonal-interannual variability? J. Climate, 21, 4424-4448 .
Resolution Increase Does Not Solve All Problems
CWRF Terrestrial HydrologyKanawha
Kentucky
Green
Tennessee
Kanawha
Kentucky
Green
Tennessee
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0 30 60 90 120 150 180 210 240 270 300 330 360Days Since Jan 1995
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ay)Precipitation
CLMCLM+CSSObserved
USGS Sta. 03320000Green River
Choi 2006; Choi et al. 2007; Choi and Liang 2010; Yuan and Liang 2010; Liang et al. 2010; Choi et al. 2013
D1
D2
D3
Urban and Built-upDryland Crpland and PastureIrrigated Cropland and PastureCropland/Grassland MosaicCropland/Woodland MosaicGrasslandShrublandMixed Shrubland/GrasslandSavanna
Deciduous Broadleaf ForestEvergreen Broadleaf ForestEvergreen Needleleaf ForestMixed ForestWater BodiesWooded WetlandBarren or Sparsely VegetatedWooded TundraMixed Tundra
atmosphere
land
ICs
LBCs
SST
CFS
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CWRF Downscaling Seasonal Climate Prediction over the U.S.
CWRFMLO
CAMGFS
CFSSST ICs
NOAA2008-2011
Monthly
Daily
Anderson, B.T., K. Hayhoe, and X.-Z. Liang, 2009: Anthropogenic-induced changes in the 21st Century summertime hydroclimatology of the Northeastern US., Climate Change, doi.10.1007/s10584-009-9673-3.
RCM Better Resolves Extremes
Northeast U.S. Assessment
Number of Rainy Days Rain Intensity Daily Rainfall 95th Percentile 1993 JJA Mean
OBS
ERI
CWRF
The reanalysis has already assimilated local observational data, while CWRF is driven by only LBCs. The CWRF skill will be enhanced if assimilating local data.
CWRF with ECP/W closure over the U.S. land
a) Spatial frequency distributions of root mean square errors (RMSE, mm/day) predicted by the CFS and downscaled by the CWRF and b) CWRF minus CFS differences in the equitable threat score (ETS) for seasonal mean precipitation interannual variations. The statistics are based on all land grids over the entire inner domain for DJF, JFM, FMA, and DJFMA from the 5 realizations during 1982-2008. From Yuan and Liang 2011 (GRL).
CWRF Improves Seasonal Climate Prediction
Statistic Metric for RCM Added Value
Consider differences in statistical distribution of skill, not just changes of mean skill.
Construct PDFs of skill over a region for both global and regional models. Focus on the part of the distribution above a critical skill level (Sc) representing minimum useful skill.
Sc
Global model (solid)
Regional model (dashed)
Added Value Index (AVI) is the area between the curves beyond the crossover point where regional model skill begins to exceed global model skill (if the crossover point exists).
Interpretation: Regional model skill is higher than global model over AVI % of the domain for the corresponding skill range.
Crossover point
After Kanamitsu and DeHaan, 2011, J. Geophys. Res., doi:10.1029/2011JD015597
Curtsey of Raymond Arritt
Interannual CORR over USA
Why Do RCM Results Differ?
• Domain: U.S. + Adjacent for CWRF & CMM5,Extended North America for NARCCAP
• Resolution: 30 km for CWRF & CMM5,50 km for all other
NARCCAP RCMs• Forcing: linear-exp relaxation in buffer zones of
14 (CWRF, CMM5), 10 (WRFG) gridslinear relaxation in 4 grids (MM5I, HRM3)domain spectral nudging (ECP2, CRCM)NARCCAP IA correlations differ largelydue to the strength of forcing integrated
• Physics: CWRF is much better than CMM5,being identical in all other settings
Different dynamics may also contribute
Climate Change Uncertainty• Biases from incomplete physics in GCMs & RCMs
• Climate sensitivities of GCMs & RCMs
• Projecting emissions scenarios
• Natural variability
Climate Change Projection by GCMs and RCMs
Propagation of GCM Present Climate Biases into Future Change Projections: Temperature
Liang, X.-Z., K.E. Kunkel, G.A. Meehl, R.G. Jones, and J.X.L. Wang, 2008: RCM downscaling analysis of GCM present climate biases propagation into future change projections. Geophys. Res. Lett., 35, L08709, doi:10.1029/2007GL032849.
U.S. + Mexico-7-6-5-4-3-2-1012345
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
Precipitation Temperature
CU BS AS
Central Great Plains-7-6-5-4-3-2-1012345
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
Precipitation Temperature
Central U.S.-7-6-5-4-3-2-1012345
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
Precipitation Temperature
Southeast U.S.-5-4-3-2-101234567
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
PGR-PCM
PKF-PCM
HGR-HAD
HKF-HAD
Precipitation Temperature
Projected U.S. Heat Wave Changes
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c) Chicago
d) Northeast US
10%
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a) Chicago
1%
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b) Northeast US
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RCM-P RCM-H OBSScenario, Period
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Scenario, Period
Kunkel, K.E., X.-Z. Liang, and J. Zhu, 2010: Regional climate model projections and uncertainties of U.S. summer heat waves. J. Climate, 23, 4447-4458.
Projections of changes in the average annual 3-day heat wave temperature (°C) for a) Chicago and b) Northeast US and of the annual average number of heat wave days for c) Chicago and d) Northeast US. The two sets of bars on the far left side of a) and b) compare the present-day annual 3-day heat wave temperature spread (from its own summer mean temperature as simulated and observed); and model biases (from observations). The simulations are arranged from left to right in order of increasing greenhouse gas concentrations. The % number at the bar top depicts the corresponding statistical significance level.
MKF MGR
EOPOBS
Optimized Physics-Ensemble Prediction
Liang et al. (2007, JCL)
Optimized Physics Ensemble Prediction of Precipitation
In summer 1993
Spatial frequency distributions of correlations (top) and rms errors (bottom) between CWRF and observed daily mean rainfall variations in
summer 1993. Each line depicts a specific configuration in group of the five key
physical processes (color). The ensemble result (ENS) is the average of all runs with
equal (Ave) or optimal (OPT) weights, shown as black solid or dashed line.
The physics ensemble mean substantially increases the skill score over individual configurations, and there
exists a large room to further enhance that skill
through intelligent optimization.
Liang et al. (2012, BAMS)
What Should We Do?• Structure Uncertainty:
- Multiple GCMs with (low, medium, high) climate sensitivities representative of the possible range
- Multiple RCMs or physics configurations with notable added values key to the application
- Multi-model ensemble with optimal weighting based on present-day climate biases
• Emission Scenario:- IPCC Representative Concentration Pathways:
RCP 8.5 & 4.5, or also RCP 6.0 & 2.6 if affordable- For projection to 2050, RCP 8.5 & 4.5 is desirable