The Interactive Ensemble Coupled Modeling Strategy

Ben Kirtman

Center for Ocean-Land-Atmosphere Studies

And

George Mason University

Science Questions

• How Does Internal Atmospheric Dynamics Impact Climate Variability?– Is ENSO Stochastically Driven or Self-

Sustained?– How Do Errors in Internal Atmospheric

Dynamics Impact Climate Predictability?

• Is it Possible to Combine Multiple Imperfect Climate Models to Improve Climate Simulations and Better Quantify Uncertainty?

Standard Approach

• A Posteriori Combinations of Ensemble Realizations (Coupled and Uncoupled)

– Does Not Isolate How Internal Dynamics Impacts Evolution of the Coupled System

• Want to Employ Ensemble Averaging As the Coupled System Evolves

CAM

MOM

Heat Flux

Momentum Flux

SST

CAM_MOM3

COLA

MOM

Heat Flux

Momentum Flux

SST

COLA_MOM3

CAM COLA

MOM

Heat Flux

Momentum Flux

SST

CAM_COLA_MOM3

CAM COLA

MOM

Heat Flux

Momentum Flux

SST

COLA_CAM_MOM3

Computational Issues (I)

• Load Balance Between Oceanic and Atmospheric Components– More Processors

• Communication of Coupling Information– Frequency Can be a Problem

• Data Management

– Dataportal (little MSS)

Computational Issues (II)

• Use (Prospect) Blackforest, Bluesky– Conversion from Compaq to IBM Difficult

• Communication: Did Not Know the Right Questions to Ask

Computational Issues (II)

• Use (Prospect) Blackforest, Bluesky– Conversion from Compaq to IBM Difficult

• Communication: Did Not Know the Right Questions to Ask• Documentation Incomplete (e.g., loadleveler geometry)• Consulting Support Excellent

• Usage (Typically 1 Node for each Component) – Blackforest: 4x75 min/simulation month (for each

atmosphere) and 4x75 (for each ocean)– Bluesky: 8x20 min /simulation month (for each

atmosphere) and 8x20 (for each ocean)

Example of CPU (GAU) Usage

• Bluesky 12 Atmospheres and 1 Ocean 100 year simulation

13 * 8 * 20 min/month * 1200 month = 41,600 CPU hours

In Regular Queue Simulation Takes about 30-50 days

In Practice We Get About 2-3 Experiments Completed Per Year

This Should Double Every Year Over the Next 5 Years

Data Management

• Some Reliance on MSS– Primarily Job Recovery

• Initially ftp’d Data Back to COLA

• Access to dataportal Grads-Dods-Server (GDS) Has Changed My Life

• Heavy usage of /ptmp

Concluding Remarks

• NCAR Facility Ideal for Testing Interactive Ensemble Coupling Strategy

• Demand on Computing to Steadily Increase Over the Next 5 Years

• Need for Local Visualization of Remote Data Large and Increasing