WRFCMAQ 2way coupled system: Part I

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WRF-CMAQ 2-way coupled system Part I

• David Wong, Jonathan Pleim, Rohit Mathur, Robert
  Gilliam, Tanya Otte, Jeffery Young
• NERL/AMD
• Frank Binkowski and Aijun Xiu
• Institute for the Environment, UNC

CMAS 08 October 6-8, 2008
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Outline

• Current operation scheme
• Motivation
• Coupling issues
• Design and features
• Overall coupled structure
• Preliminary results

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Current operation scheme
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Motivation

• Shortcomings of the current way of running met
  model- MCIP-CMAQ
• 32-bit data storage in files
• excessive data interpolation
• lack of feedback (direct and indirect effect)
  from CMAQ to the met model

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Coupling Issues

• Compatibility of met model and CMAQ
• model physical aspects
• computational aspects
• Coupling tool

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Coupling Issues compatibility

• Model physical aspects
• map projection
• coordinate system and grid format
• layer structure
• time step size
• etc

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Coupling Issues compatibility (contd)

• Computational aspects
• domain decomposition
• processor and subdomain mapping

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Coupling Issues compatibility (contd)

• Runtime System Library, RSL
• RSL (MM5 and WRF), RSL-Lite (WRF)
• RSL-Lite is slightly faster than RSL

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Coupling Issues Tools

• Earth System Modeling Framework (ESMF)
• Other choices OpenMI (UK), Model Coupling
  Toolkit (MCT) (ANL)
• M3IO IOAPI Buffered file

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Design Strategy

• Maintain integrity of WRF and CMAQ models
• Minimal code changes
• Keeping the same IOAPI calls
• Easy to incorporate new version of WRF
• Efficiency Low coupling overhead
• buffered file for data transfer (forward and
  backward)
• buffered file always holds two time steps of data
  allowing interpolation
• Flexibility easy to add feedback parameters and
  outputs

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Features

• Flexible time stepping
• CMAQ can be called every WRF timestep or at any
  user defined multiple
• Simple run time switch of feedback
• Subdomain tracking
• Switch back to disk I/O file for uncoupled mode

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WRF-CMAQ system overview
WRF
CMAQ
emission data
Solve.F
vdiff biogenic emis plume rise surface
flux hadv zadv hdiff cldproc chem aero
physics drivers
radiation microphysics
initial conditions
dynamics
aq_prep
boundary conditions
met data
CMAQ (time, Dt)
feedback
aerosol data
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Example of a call frequency ratio of 4
time line
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Preliminary results
Offline 41
O3
PM25
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Preliminary results (contd)
41 11
O3
PM25
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Execution time

• 44502

21523
00421
22518
45207
90252
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Preliminary results (contd)
41 w/o w/ feedback
O3
PM25
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Preliminary results (contd)
w/ feedback 41 11
O3
PM25
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Preliminary results (contd)
w/ feedback 4x8 2x4
O3
PM25
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Execution time (contd)
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• To be continued