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

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

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

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

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

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

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

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

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

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?

Coupling Interface at 30 km Stand Alone TIME-GCMCoupled TIME-GCM Plots of Neutral Temperature

Upper Stratosphere Stand Alone TIME-GCMCoupled TIME-GCM Plots of Neutral Temperature

Mesosphere Stand Alone TIME-GCMCoupled TIME-GCM Plots of Neutral Temperature

Thermosphere Stand Alone TIME-GCMCoupled TIME-GCM Plots of Neutral Temperature

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