Initial Results from the North American Regional Climate Change Assessment Program (NARCCAP)

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Initial Results from the North American Regional
Climate Change Assessment Program (NARCCAP)
Linda O. Mearns, NCAR Chris Anderson, Ray Arritt,
Iowa State, George Boer, CCCma, Daniel Caya,
OURANOS, Phil Duffy, LLNL, Filippo Giorgi, ICTP,
William Gutowski, Iowa State, Isaac Held, GFDL,
Richard Jones, Hadley Centre, Rene Laprise,
UQAM, Ruby Leung, PNNL, Ana Nunes, Scripps,
Jeremy Pal, ICTP, Yun Qian, PNNL, John Roads,
Scripps, Lisa Sloan, UC Santa Cruz, Ron
Stouffer, GFDL, Gene Takle, Iowa State, Warren
Washington, Tom Wigley, NCAR, Francis Zwiers,
CCCma
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NARCCAP Goals

• Explore multiple uncertainties in regional and
  global climate model projections at the regional
  scales
• Develop multiple high resolution regional climate
  scenarios for use in impacts models
• Further evaluate regional model performance over
  North America
• Explore some remaining uncertainties in regional
  climate modeling (e.g., sensitivity to domain
  size, importance of compatibility of physics in
  nesting and nested models)
• Create greater collaboration between US and
  Canadian climate modeling groups, as well as with
  the European modeling community

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Domain Sensitivity Study
Each simulation lasts for one year (1979) using
NCEP/DOE reanalysis b.c.
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? Z500
7902
7905
7908
7911
ISU MM5
SIO RSM
CRCM
PNNL MM5
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? Prec
7902
7905
7908
7911
ISU MM5
SIO RSM
CRCM
PNNL MM5
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Nine Subregions Defined for Analysis
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Annual Cycle of Precipitation mm/month
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Annual Cycle of Tmax K
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Annual Cycle of Tmin K
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Bias Annual P vs. T
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Bias Annual P vs. T
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Bias Annual Tmax vs. Tmin
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Bias Annual Tmax vs. Tmin
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500 hPa Z Bias - Feb 79
Exp 0.0
Exp 0.1
Exp 0.2
ISU MM5
CRCM
PNNL MM5
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500 hPa Z Bias - May 79
Exp 0.0
Exp 0.1
Exp 0.2
ISU MM5
CRCM
PNNL MM5
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Summary

• An initial study has been performed to examine
  the sensitivity of RCM simulations to domain
  size.
• Results suggest weak relationship between bias in
  large scale circulation and T/P.
• MM5s tend to have larger 500 hPa height biases.
• RSM and CRCM have larger precip. biases during
  summer.
• HADRM3 has larger warm bias throughout the
  domain.
• CRCM tends to reduce amplitude of diurnal T
  cycle.
• Models exhibit the largest spread in P in the
  Southeast.

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Summary

• There are no obvious trends in T P biases as
  the domain gets larger,
• Although bias in large-scale circulation
  generally increases with domain size.
• Use smallest (least computationally demanding)
  domain
• www.narccap.ucar.edu