A TIMEGCM CAM Multiexecutable Coupled Model Using ESMF and InterComm

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A TIME-GCM CAM Multi-executable Coupled Model
Using ESMF and InterComm

• Robert Oehmke, Michael Wiltberger, Alan Sussman,
  Wenbin Wang, and Norman Lo

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Introduction

• TIME-GCM is a model of the upper atmosphere
• CAM is a model of the lower atmosphere
• This project coupled TIME-GCM and CAM
• CAM is lower boundary forcing for TIME-GCM
• Models run side by side as separate executables
• ESMF in CAM interpolates between grids
• InterComm sends data between executables

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Motivation

• Scientific
• Current TIME-GCM model does not capture observed
  hemispheric asymmetries
• Including more complex lower boundary forcing
  from the lower atmosphere model should help this
• Technical
• Demonstrate efficacy of ESMF InterComm
  combination
• Use of these tools makes coupling models easier

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ESMF

• Earth System Modeling Framework
• Provides standard interfaces for models
• Provides standard structure for transferring data
  between models
• Provides a range of utilities to ease coupling
• Data regridding
• Data redistribution
• Time management
• Error handling

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InterComm

• Library developed at the U. of Maryland by Alan
  Sussman and colleagues
• Allows data to be transferred between separate
  executables
• Allows communication between parallel codes for
  any data distribution or number of processors
• Allows coupling with minimal code modification
• Contributed interfaces facilitate moving data
  in/out of ESMF components

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CAM

• NCAR Community Atmosphere Model
• CAM 3.0 is the latest generation of the NCAR AGCM
• Includes packages for clouds, ice, and aerosols
• MPI based parallel code
• Using Eulerian spectral dynamics option
• Using 128x64 Gaussian Grid

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TIME-GCM

• Thermosphere-Ionosphere-Mesosphere-Electrodynamics
  General Circulation Model
• Developed at HAO by Ray Roble and colleagues
• Simulates circulation, thermal, and compositional
  structures from 30-500km
• Continuous efforts to compare model results with
  ground and satellite observations
• MPI based parallel code
• Using 72x36 regular latitude longitude grid

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CAM to TIME-GCM Coupling

• Takes place at the 10mb pressure level
• Transfers temperature from CAM to TIME-GCM
• Transfers geopotential from CAM to TIME-GCM
• Quantities are regridded via bilinear
  interpolation
• Models each executing in parallel during coupling
• Models running as separate executables while
  coupling
• Coupling occurs every timestep

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Coupled System
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Current Status

• We have the coupled system running
• Data flows correctly between models
• We have some preliminary output
• Next Steps
• Scientific investigation of coupled system
• Improvement of coupling
• Other interpolation methods?
• More data flowing between models?

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Coupling Interface at 30 km
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Upper Stratosphere
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Mesosphere
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Thermosphere
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Conclusions

• InterComm and ESMF form an effective combination
  for creating multi-executable coupled models
• Using these tools allowed coupling with minimal
  code modification
• There are difference in the preliminary output
  between stand alone and coupled, but analysis is
  still needed