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

1. A TIME-GCM CAM Multi-executable Coupled Model Using ESMF and InterComm Robert Oehmke, Michael Wiltberger, Alan Sussman, Wenbin Wang, and Norman Lo

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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

8. 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

9. CAM TIME-GCM Cam Setup TIME-GCM Setup Initialize InterComm Create Block Regions Initialize InterComm Create Block Regions Register Regions Commit Regions Initialize ESMF Create Data objects Translate to InterComm Setup Regridding CAM Calcs Regrid Temperature Regrid Geopotential Receive Temperature Receive Geopotential InterComm InterComm Send Temperature Send Geopotential TIME-GCM Calcs Coupled System

10. 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?

11. Plots of Neutral Temperature Stand Alone TIME-GCM Coupled TIME-GCM Coupling Interface at 30 km

12. Plots of Neutral Temperature Stand Alone TIME-GCM Coupled TIME-GCM Upper Stratosphere

13. Plots of Neutral Temperature Stand Alone TIME-GCM Coupled TIME-GCM Mesosphere

14. Plots of Neutral Temperature Stand Alone TIME-GCM Coupled TIME-GCM Thermosphere

15. 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