# Presentation: 884574

## NCEP Climate Ensemble Forecast System: model configuration, products and plans

- Suru Saha and Malaquías Peña
- Environmental Modeling Center
- NCEP

## An Overview of New and Future Developments with the NCEP Climate Forecast SystemSuranjana Saha and Hua-Lu PanClimate Modeling Team,EMC/NCEP

## The NCEP Climate Forecast was made operational in      August 2004

**The NCEP Climate Forecast was made operational in      August 2004**
** ****Currently, two fully-coupled nine-month forecasts are made every day**
** ****The present CFS operational system is frozen**
** ****Development work is underway at EMC to improve the CFS**
**We anticipate a new CFS implementation will take in January 2010**

## CFS configuration

**1. Atmospheric component**:

**2. Oceanic Component**

**3. Coupled model**

*** **Once-a-day coupling with no flux corrections
*** **Sea ice extent taken as observed climatology

- GFDL MOM3
*** **1/3 in tropics; 1 in extratropics; 40 layers
*** **Quasi-global domain (74S to 64N)
*** **Free surface
*** **Daily update from the 14-day lag GODAS analysis.

- Global Forecast System (GFS) 2003. T62 L64

## Hindcast CFS 

**For calibration (bias removal) and **
**a-prior skill assessment**
- 15-member ensemble
- 25 years from 1981-2004
- 10 months lead runs
- Initial atmospheric states: Five 00Z analyses centered on the 1st, the 11th and the 21th day of each month from the Reanalysis-2 archive
- Initial ocean states: the 1st, the 11th and the 21th  of each month from NCEP GODAS (Global Ocean Data Assimilation System)

## Slide 6

## Two main components:

**For a new CFS implementation**** **
**Two main components:**
**CFS Reanalysis (1979-2007) T254L64**
**CFS Retrospective Forecasts (1981-2007) T126L64**

## For a new CFS implementation (contd)

**For a new CFS implementation (contd)**
**Analysis Systems :****	****GSI, GODAS, GLDAS**
**Atmospheric Model :****	****GFS**
**Ocean Model :****	****	****MOM4 (1/4****0 ****at the ****	****	****	****	****	****Equator, 1/2****0 ****at globally ****	****	****	****	****	****beyond 10****0****N and 10****0****S**
**	****	****	****	****	****SEA ICE MODEL**

## Proposed Time-Line for the next CFS implementation in January 2010

**October 2006**
- In anticipation of the operational implementation of the sigma-p version of the **GSI** in February 2007, start testing this version for a few particular years in the 1979-2006 period, where changes in satellites will lead to new corrections in radiance measurements.
- Run the GSI for a few random years and save the fluxes.
- (Saha, Treadon, van Delst, Derber, Kliest, Woollen, Pan, Kistler, White)

## Proposed Time-Line for the next CFS implementation in January 2010

**June 2007**
- In anticipation of the ESMF version of the coupler and MOM4, start testing the new **GODAS** (with MOM4 and sea ice) and **GLDAS** (with Noah Land model and observed precipitation) with fluxes obtained from atmospheric GSI analyses of the few random years.
- (Behringer, Mitchell, Sheinin, Wang, Wu, Nadiga, Stokes, Pan, Moorthi, Grumbine, Saha, Meng, Wei)

## Proposed Time-Line for the next CFS implementation in January 2010

**August 2007**
- In anticipation of the operational implementation of the next **GFS**, start pilot studies with the first “prototype” of the fully coupled CFS reanalysis, which will include the GSI (with new GFS), GODAS and GLDAS.
- (Saha, Pan, Iredell, Moorthi, Derber, Behringer, Mitchell, Meng, Yang, Treadon, Sheinin, Woollen, Kistler)

## Proposed Time-Line for the next CFS implementation in January 2010

**January 2008**
- Begin Production and Evaluation of the CFS Reanalysis for the full period from 1979 to 2007 (29 years)
- Reanalysis Team: Saha, Thiaw, Wang, Nadiga, Wu, Lu.
- Evaluation Team: EMC and CPC Personnel

## Proposed Time-Line for the next CFS implementation in January 2010

**July 2008**
- Begin running CFS Retrospective Forecasts for 2 initial months: October and April, and evaluate the monthly forecasts as well as the seasonal Lead-1 DJF and JJA forecasts.
- Hindcast Team: Saha, Thiaw, Wang, Nadiga, Wu, Lu
- Evaluation Team: EMC and CPC Personnel

## Proposed Time-Line for the next CFS implementation in January 2010

**January 2009**
- Operational Implementation of the CFS Reforecast Project (for the rest of the 10 calendar months) in the proposed slot of REFCST in the NCEP production suite.
- (NCO personnel, Saha, Moorthi, Pan and Thiaw)

## January 2010: Operational implementation of the next CFS monthly and seasonal forecast

**November 2009**
- Begin computing calibration statistics for CFS daily, monthly and seasonal forecasts. Prepare CFS Reanalysis and Retrospective Forecast data for public distribution.
- (Saha, Thiaw, Pan and CPC personnel)
**January 2010: Operational implementation of the next CFS monthly and seasonal forecast**

## Proposed Hindcast Design:

**For Calibration and Skill Estimates**:
- There will be 1 run every day over the entire 1981-2007 period, out to 60 days at a higher resolution (TBD) for the **MONTHLY** forecast.
- Every other day, the resolution of the run will decrease to T126L64 after 60 days and then go out to 1 year for the (long lead) **SEASONAL** forecast.

## Proposed Operational Real Time Forecast Design:

**GDAS, GLDAS and GODAS will be brought up to real time (unlike the current configuration, which is 7 days old)**
**For the Monthly forecast issued once a week:**
- Every day, a maximum of 8 runs/day or a minimum of 4 runs/day, at high resolution (TBD) out to 60 days.
**For the Seasonal forecast issued twice a month:**
- Every day, an extension of at least 4 runs/day of the high-resolution monthly forecasts at a lower (T126L64) resolution beyond 60 days, out to 1 year.

## Alternate CFS ensemble strategyproposed by Zoltan Toth and Malaquias Pena 

- Environmental Modeling Center
- NCEP

## Initial Perturbation: Lagged ensemble scheme 

**t=0**

**t =-1**

**t =-2**

**t =-3**

**target**

**time**

******* **Allows constant operational center computer usage.
******* **Users can form 40-60 member ensemble at any time.

******* **Different size perturbations.
******* **Not centered
*** **Initial uncertainty not incorporated in initial perturbations
*** **On average, older runs tend to deteriorate accuracy for short leads

**RMS error and ensemble spread**

## CFS RMS error decomposition

**Improved Initial Pert**

**Red**: rmse of ensemble average forecast
**Blue**: Estimate rmse of individual members
**Black**: “optimal” rmse of ensemble average

**CFS RMS error decomposition**

## Two alternatives:

- 1) For intra-seasonal: Extend GFS ensemble from 15 to 45 days, with bias corrected SSTA forcing. This needs to be done anyway for up to 15 days with boundary condition perturbations.
- 2) Use Breeding or Ensemble Transform (ET) technique for perturbing the CFS system.

## Improved SSTs & boundary pert of GFSE

- Implementation needs to be wise to discriminate between SST driving Atmosphere and the other way around cases.

- SST Anomaly field needs to be consistent to the GFS to reduce initial shock.

- NORTHERN PACIFIC CASE

## Cai et al. (2003) results with Zebiak and Cane model:

- Rescaling done every 1-3 months (insensitive to interval and to norm)
- Bred Vector growth rate is strongest before and after ENSO events.
- Bred Vectors can be applied to improve the forecast skill and reduce the impact of the “spring-barrier”.

**Monthly Amplification Factor of Bred Vector**

**Background ENSO**

**La Niña**

**La Niña**

## Weights for (Multi) model forecast

- More climate prediction systems are becoming available
- Should we include all of them? Should we mask out variables and regions where model was not skillful in past runs?
- Can sophisticated optimization procedures outperform the simple (equal weights) average?
- Need to carry out sufficiently long retrospective forecast data to identify and remove systematic errors and to produce stable optimal weights.

- [-- Participant models: Demeter +   --]

-   [--- Consolidation methods ---]

- AC. Tropical Pacific SST

## Conclusions

- The CFS system is a major step forward for Dynamical seasonal predictions at NCEP. It has predictive skill in the equatorial tropical SST comparable to the statistical methods.
- Software, retrospective and operational data and documentation are freely available on the internet.
- Skill improvements are sought in the next CFS version by upgrading and incorporating model components (ice, ocean, land, atmosphere)
- Potentially, synergistic skill improvement, at least for the 1-2 lead months, if optimizing initial ensemble perturbations.
- SST anomalies can be used as initial perturbations for GFSE.
- Post-processing (calibration and combination) methodologies are being tested to increase accuracy and quality.