# Presentation: 271684

## Running the Community Climate Simulation Model (CCSM) at NERSC

**National Center for Atmospheric Research****Boulder, Colorado**

*CAM T340- Jim Hack*

**Notes:**
(CCSM) is a fully-coupled, global climate model that provides state-of-the-art computer simulations of the Earth's past, present, and future climate states.
White shows water vapor, orange shows actual precip
While this particular run hasn’t been checked against real data, it does show many of the features that we look for with CCSM such as cyclonic activity and daily rain fall over south america.

## 1870 Control Run

_**0**_

_**500-1000**_

- _Years_ 	(constant-1870-conditions control run)

- TS (Globally averaged surface temperature)

**Notes:**
Run atmosphere 1870 over and over, ocean doesn’t have any time dependant forcing.
This gives us the variability of the model.

## 5 Member 1870-2000 Historical Ensemble

_**380**_
**b**

_**400**_
**c**

_**420**_
**d**

_**440**_
**e**

_**360**_
**a**

- _0_

_**500**_

- _Years_

- TS (Globally averaged surface temperature)

**1870**

**2000**

**A**

**B**

**C**

**D**

**E**

**1870**

**1870**

**1870**

**1870**

**2000**

**2000**

**2000**

**2000**

**Notes:**
Next, starting at different points on the control run, we run historical ensembles from 1870-2000, and compare them with real data

## CCSM IPCC Graph

**Notes:**
SRES  A1: a future world of very rapid economic growth, low population growth and rapid introduction of new and more efficient technology. Major underlying themes are economic and cultural convergence and capacity building, with a substantial reduction in regional differences in per capita income. In this world, people pursue personal wealth rather than environmental quality.  The A1 scenario family develops into three groups that describe alternative directions of technological change in the energy system.  The three A1 groups are distinguished by their technological emphasis: fossil intensive (A1FI), non-fossil energy sources (A1T), or a balance across all sources (A1B). 
SRES A2: a very heterogeneous world. The underlying theme is that of strengthening regional cultural identities, with an emphasis on family values and local traditions, high population growth, and less concern for rapid economic development. 
SRES B1: a convergent world with rapid change in economic structures, "dematerialization" and introduction of clean technologies. The emphasis is on global solutions to environmental and social sustainability, including concerted efforts for rapid technology development, dematerialization of the economy, and improving equity. 
SRES B2: a world in which the emphasis is on local solutions to economic, social, and environmental sustainability. It is again a heterogeneous world with less rapid, and more diverse technological change but a strong emphasis on community initiative and social innovation to find local, rather than global solutions. 

## Model Vs Observations

***Climate of the last Millennium***

- Caspar Ammann
- NCAR/CGD

**Notes:**
The coupled models that came out of the 1990s were able to simulate both historical and present day climate. 
The CCSM’s strength lies in its ability to simulate the Earth’s climate over long time periods with high accuracy and without artificial corrections added to the simulation (known as “flux-corrections”) to maintain stability.
Figure 3 shows a comparison of a recent CCSM simulation of the past millennium, carried out by Caspar Ammann from NCAR, using a very low resolution (T31) version of the CCSM (red) with a reconstruction of the earth’s past climate from proxy data (green).  While not perfect, the model is able to duplicate the long term climate variations, particularly after the year 1300.  The large cooling excursions show that the model overreacts to volcanic events compared to observations.  Simulations of the earths climate during the instrumental period (years 1900 to 2000) using the full range of natural and anthropogenic forcings show very good agreement with observations (black).  
When the exact same simulation is made without the man-made greenhouse gasses and sulfate aerosols (blue), the simulation strongly diverges from the observations after the 1970s, and actually shows a slight cooling trend.   This demonstration that the recent large increase in global surface temperature relative to the “normal” climate envelope observed over the last millennium can only be recreated if the man-made greenhouse-gasses are included in the simulation is the “smoking-gun” evidence that human activities are changing the earth’s climate.

##  CCSM 3.0 T85 on bassi

***Atmosphere***
***128 pes***

*Ocean*
*40 pes*

*Coupler*
*8 pes*

*Sea Ice*
*16 pes*

*Land*
*16 pes*

- Small number of processors (208), but long run time (16 days)
- Want 5 model years/day
- Queue is generally 3 days long
- Model runs roughly 1 model year/3 hours or max 4 years/run slot

**Notes:**
8.4 model years/wallclock day
CCSM doesn’t fit NERSC’s optimal job size/shape
Given current queue structure, our jobs take way too long to run
Optimally, we’d like to have a small job queue that would allow us to run 24/7

##   HPC dimensions of Climate Prediction

_*Data Assimilation*_

_*New Science*_

_*Spatial*_
*  *_*Resolution*_

_*Ensemble size*_

_*Timescale*_

_*Better Science*_

- (parameterization → explicit model)

- (new processes/interactions not previously included)

- (simulate finer details, regions & transients)

- (quantify statistical properties of simulation)

- (decadal prediction/ initial value forecasts)

- (Length of simulations)

- Lawrence Buja (NCAR) / Tim Palmer (ECMWF)

**Notes:**
Given a finite amount of computing capability (red hexagon), modeling groups budget 

All require much greater computer resource 
and more efficient modelling infrastructures

##   HPC dimensions of Climate Prediction

_*Spatial *_
* *_*Resolution*_
-       (x*y*z)

_*Ensemble size*_

_*Timescale*_
-   (Years*timestep)

**Today**
**Terascale**

_**5**_

_**50**_

_**500**_

_**Climate Model**_

**2010**
**Petascale**

_**1.4°**_
_**160km**_

_**0.2**__**°**_
_**22km**_

**AMR**
**1000**

**400**

_**1Km**_

**Regular**** ****10000**

_**Earth System Model**_

_**100yr***_
_**20min**_

_**1000yr***_
_**3min**_

_**1000yr * ?**_

**Code Rewrite**

**Cost Multiplier**

_*Data Assimilation*_

_**ESM+multiscale GCRM**_

_*New Science*_

_*Better Science*_

*  **HPC dimensions of Climate Prediction*

**?**

- Lawrence Buja (NCAR)

**2015**
**Exascale**

**Notes:**
Given a finite amount of computing capability (red pentagon)
AMR Adaptive Mesh Refinement
Our development team lags approximately 3 years behind new computer technology

## GlobalGeneral 

- GlobalGeneral
- Circulation

- Continentallarge-scaleflow

- Regional

- local

- Paleoclimate

- BGC/Carbon CycleSpin-ups

- MJO convergence

- Resolve Hurricanes

**IPCC AR4**
**2004  4TF**

**IPCC AR3**
**1998  **

**IPCC AR5**
**2010 500TF**

**CCSM Grand**
**Challenge**
**2010 1PF**

## Community Climate System Model (CCSM)

_**Current Configuration**_
- Hub and spoke design with 5 executables
- Exchange boundary information through coupler
- Each code quite large: 60-200k lines per code
- Need 5 simulated years/day --> Must run at “low” resolution
- Standard configuration run at scaling sweetspot of O(200) processors
_**Petascale Configuration**_
- Single executable
- 5 years wall-clock day
- Targeting 10K - 120K processors per simulation
- CAM    @ 0.25°  (30 km, L66)
- POP     @ 0.1°   Demonstrated 8.5 years/day on 28K Bluegene
- Sea-Ice @ 0.1°  Demonstrated 42 years/day on 32K Bluegene
- Land     @ 0.1°
- Cpl

## Data Processing

-  Ample disk space (We use up to 600 GB at a time)
-  Ample memory (We use 2-4 GB)
-  Long serial interactive jobs are fine
-  Software we use includes the netCDF Operators (NCO),     	NCAR Graphics Command Language (NCL),            	Ferret 5.81, and more.
- “It's dependable, reliable, robust, and fits my requirements quite well.”  -- Gary Strand

## Thanks!  Any Questions?

*Thanks!  Any Questions?*