# Presentation: 228064

## 1ST PREDICTABILITY / ENSEMBLE MEETING

**MOTIVATION **
**Existing venues** (Branch meetings) –
- 				Not enough time for detailed scientific discussions
**Number of people working on predictability increased** (10+) –
- 				Need more 	Communication
- 						Cross-branch fertilization
*Research -**	*	Exchange ideas, provide feedback (quality)
*Development -* 	Share procedures and software (effectiveness)
**Management **(and many participants) - 	Supportive
**FORMAT**
*Once every four weeks, Tuesday 2(-4) pm (from Oct 21 on)*
*	**Open discussion on important issues*
*	**Presentations and discussion on current research/development work*

## 1ST PREDICTABILITY / ENSEMBLE MEETING

**PARTICIPANTS **
**Global Ensemble (1991):****	****	****	****Regional Ensemble (1995):**
- Lacey Holland	Products, web		Jun Du		Parallel, implementat.
- Dingchen Hou	Model error		Jeff McQueen	Coordinator
- Mozheng Wei	Initial perts.		BinBin Zhou	Products, web
- Dick Wobus	Parallel, implem.
- Yuejian Zhu	Verification, prod. 	**Adaptive Observations (1995):**
- 						Lacey Holland 	WSR support
-  **Coupled Ocean-Atm. Ensemble (02):****	**
- Guocheng Yuan Research 		**Wave Ensemble (2003?):**
- 						Hsuan Chen?	Experimentation?
**TOPICS FOR FUTURE MEETINGS**
- Model errors and ensemble forecasting
- Can an ensemble help find a single best forecast?
- Initial perturbations
- New products
- 	Detailed presentations before branch briefings / other meetings

## NORTH AMERICAN ENSEMBLE FORECAST SYSTEM

**JOINT CANADIAN-US**
**RESEARCH, DEVELOPMENT, AND IMPLEMENTATION PROJECT**
- Can provide framework or reference for cross-branch ensemble collaboration

## NORTH AMERICAN ENSEMBLE FORECAST SYSTEM PROJECT

**GOALS:      ****Accelerate improvements in operational weather forecasting**
- 	*through Canadian-US collaboration*
**Seamless (across boundary and in time) suite of products**
- 	*through joint Canadian-US operational ensemble forecast system*
**PARTICIPANTS: ****	****  **Meteorological Service of Canada (CMC, MRB)
- 		  US National Weather Service (NCEP)
**PLANNED ACTIVITIES:  **Ensemble data exchange (June 2004)
- 				   Research and Development -*Statistical post-processing*
*	**	**	*(2003-2007)*	**           -Product development*
*	**	**	**	**	**           **-Verification/Evaluation*
- 				   Operational implementation (2004-2008)
**POTENTIAL PROJECT EXPANSION / LINKS: **
- 		   Shared interest with THORPEX goals of
*	**	**	**Improvements in operational forecasts*
*	**	**	**International collaboration*
- 		   Expand bilateral NAEFS in future
*	**	**	**Entrain broader research community*
*	**	**	**Multi-center / multi-national ensemble system:*
*	**	**	**	**NCEP, MSC, ECMWF, JMA, FNMOC?*

## NAEFS ORGANIZATION

***Meteorological Service of Canada******	******National Weather Service, USA***
***	******	******MSC ******	******	******	******	******	******NWS******	***

- _J.-G. Desmarais (Implementation)_
- Peter Houtekamer (Science)

- _Zoltan Toth (Science)_
- D. Michaud/B. Gordon (Implementatn)

***PROJECT OVERSIGHT***

***JOINT TEAM MEMBERS***

*Meteorological Research Branch MRB*
- Gilbert Brunet 	Herschel Mitchell
- Laurence Wilson
*Canadian Meteorological Center CMC*
- Richard Hogue	Louis Lefaivre
- Richard Verret

*Environmental Modeling Center EMC*
- Lacey Holland	Richard Wobus
- Yuejian Zhu
*NCEP Central Operations NCO*
- TBD
*Hydrometeor. Prediction Center HPC*
- Peter Manousos
*Climate Prediction Center CPC*
- Mike Halpert	David Unger

- Michel Beland, Director, ACSD
- Pierre Dubreil, Director, AEPD

- Louis Uccellini (Director, NCEP)
- D. Perfect (Interntnl. Coordinat., NWS)

***PROJECT CO-LEADERS***

## NAEFS OVERVIEW

- Febr. 2003	MSC – NOAA / NWS high level agreement (Long Beach)
- May 2003	Planning workshop (Montreal)
- Oct 2003	Research, Development, and Implementation Plan complete
- Spring 2004	2nd Workshop (WWB)
- Sept 2004	Initial Operational Capability
- 2008		Final Operational Implementation
***	******	******	****	*

## NAEFS 

**RESEARCH, DEVELOPMENT, & IMPLEMENTATION PLAN**

**MAJOR TASKS**
- Exchange ensemble data between 2 centers
- Statistically bias-correct each set of ensemble
- Develop products based on joint ensemble
- Verify joint product suite, Evaluate added value
**COORDINATED EFFORT**
- 	Between Research / development and operational implementation
- 	Between MSC and NWS
- 			NCEP would carry out most tasks anyway
- 		Broaden research scope -		Enhanced quality
- 		Share developmental tasks -		Increased efficiency
- 		Seamless operational suite-		Enhanced product utility

## NAEFS 

**STEP-WISE APPROACH**
- 0)	Initial Oper. Capability – 	Existing products based on other ensemble
- 1)	First Implementation – 	Basic joint forecast system (not comprehens.)
- 2)	Second Implementation -	Refinement (Full system)
- 3)	Final Implementation -	High impact weather enhancements

**NAEFS **
**RESEARCH, DEVELOPMENT, & IMPLEMENTATION PLAN**

## NAEFS MAJOR TASKS

**DATA EXCHANGE**
- Identify common set of variables/levels for exchange ~40 fields
- Use GRIB1 with NCEP ensemble PDS extension
- Use native resolution for transfer, convert to common 1x1 (2.5x2.5) grid
- Every 12 hrs, out to 16 days (MSC out to 10 days until next summer)
- 		Subset available on a non-operational basis

## LIST OF VARIABLES IDENTIFIED FOR ENSEMBLE EXCHANGE BETWEEN CMC  - NCEP

**Blue :  items have been added in prototype script for expanded CMC dataset.**
- Red   : items can be easily added to the expanded dataset via an autoreq for CMC; next implementation period for NCEP
- *    these will be added within 1 month for CMC
- **  these will be added within 2 months for CMC
- Green: items that require further consideration and resources

- Black :  data presently exchanged
**Blue :  items have been added in prototype script for expanded CMC dataset.**
- Red   : items can be easily added to the expanded dataset via an autoreq for CMC; next implementation period for NCEP
- *    these will be added within 1 month for CMC
- **  these will be added within 2 months for CMC
- Green: items that require further consideration and resources

**LIST OF VARIABLES IDENTIFIED FOR ENSEMBLE EXCHANGE ****BETWEEN CMC  - NCEP**

## NAEFS MAJOR TASKS – BIAS CORRECTION

**ISSUES**
**Exchange raw or bias-corrected forecasts?**
- 	To ensure 100% backup capabilities =>
- 		Exchange raw data, use same bias-correction at both centers
**Bias-correct before or after merging different ensembles?**
- Sub-components have different biases etc => Calibrate before merging
**Correct univar. prob. distribution functions (pdf) or individual members?**
- 	Users need both – eg, joint probability products (prob hi winds and lo temp)
- 	Correct individual members => pdf falls out free
**Correct for expected value enough?**
- 	No, need to correct for bias in spread => multi-step approach:
- 		a) 	Shift all members
- 		b)	Adjust spread around mean
- 		c)	Reduce temporal variations in spread (if too confident, Unger)
**How much training data (forecast – verifying analysis pairs) enough?**
- 	Open research question =>
- 	Need flexible algorithm that can be used either with
- 		Small amount of data – Smooth adjustments to eliminate gross error
- 		Large amount of data – Finer adjustments possible

## BIAS CORRECTION

*STATISTICAL SAMPLING*  (Increase sample size):
- 	Use data from surrounding grid-points (with Gaussian weighting)
- 	Use climate means if available *and* forecast system is stable
- 	Use most recent past data with decaying averaging otherwise
- 		Ability to quickly learn bias of new NWP systems before upgrade
- 	Adjust temporal/spatial sampling domain to optimize performance
**REMOVE BIAS:****	**Compare time mean fields
- 1st moment = Ensemble mean - D	     2nd moment = Ensemble spread * R

- FIRST MOMENT
- D = DIFFERENCE BETWEEN
- Ensemble mean forecast
- and
- Verifying analysis

***TWO GOALS:***
- 	Adjust sample – ensemble time trajectories, covariances, only *then*
- 	Construct bias-corrected pdf for individual variables
***APPROACH – ****Bias corrected anomalies on model grid, then downscaling*
**1)****	****ESTIMATE BIAS:****	****Compare time mean fields**

- SECOND MOMENT
- R = RATIO BETWEEN
- Ensemble mean error
- and
- Ensemble spread

## Slide 13

## Slide 14

## NAEFS MAJOR TASKS – PRODUCT DEVELOPMENT

**TYPES OF PRODUCTS**
**A)****	****Joint ensemble** (bias-corrected ensembles merged on model grid)
**B)****	****Anomaly joint ensemble**
-  Express forecast anomalies from reanalysis climatology –
- 						(model grid, easy to ship)
**C)****	****Local joint ensemble forecast** (local, bias-corrected, downscaled)
- 	Add forecast anomaly to observed climatology at
- 		Observational locations or
- 		NDFD grid
**D)****	****Host of products** based on any of 3 choices above
- Gridded, graphical, worded, week 2, etc for
- Intermediate users (forecasters at NCEP, etc)
- End users (automated products at MSC)
- Specialized users
- 	General public
**E)****	****High impact weather products**
- Assess if general procedures above are adequate or can be enhanced for forecasting rare/extreme events

## BIAS CORRECTION / DOWNSCALING, APPROACH

**FORM FORECAST ANOMALIES:****	**

- 	**BIAS CORRECTED LOCAL FORECAST**
- 		*Only climatology is stored at high resolution, anomaly forecast is on coarse grid*

- FIRST MOMENT
- Forecast anomaly
- Plus
- Local climate mean

- SECOND MOMENT
- Multiply Standardized Anomaly
- and
- Local climate standard deviation

- 	**BIAS-CORRECTED STANDARDIZED ANOMALY FORECAST ON MODEL GRID**** **
- 		*Temporal/spatial resolution can degrade with lead time / loss of predictability*
**4)****	****COMBINE ENSEMBLES FROM DIFFERENT CENTERS:**
- 	Follow steps 1-3 for each ensemble separately
- 	Determine weights for each ensemble based on error statistics (D. Unger)
- 	Combine anomalous ensemble forecasts (with weights)
**DOWNSCALE:****	**
- 	Add coarse resolution forecast anomaly to NDFD (or other local) climate distribution

- FIRST MOMENT
- Ai = DIFFERENCE BETWEEN
- Each ensemble forecast
- and
- Reanalysis climate mean

- SECOND MOMENT
- SAi = RATIO BETWEEN
- Anomaly
- and
- Reanalysis Standard Deviation

## NAEFS MAJOR TASKS – VERIFICATION

**ISSUES **
- Data sets/archiving – 				Center specific
- Software to compute common set of statistics – 	Shared by 2 centers
- Modular subroutines - common 		Input
- 						Output
- 						Options/parameters
- Verifying against both analysis fields and observations
- Special product / high impact weather forecast evaluation

## NAEFS 

**FUTURE JOINT RESEARCH OPPORTUNITIES**

**Ensemble configuration - **
- 		Model resolution vs. membership, etc
**Representing model errors in ensemble forecasting** –
- 		High priority research area, collaboration possible
**Initial ensemble perturbations** –
- 		Compare 2 existing systems, may improve both
**Ensemble forecasting on different scales**:
- 	Regional ensemble forecasting – No activities at MSC, maybe in 2 yrs
- 	3-6 weeks – seasonal:	        Opportunities for research collaboration

## NAEFS - BENEFITS

**Two independently developed systems combined**, using different:
- 	Analysis techniques
- 	Initial perturbations
- 	Models
- 		***Joint ensemble may capture new aspects of forecast uncertainty***
**Procedures / software can be readily applied on other ensembles:**
- 	ECMWF
- 	JMA
- 	FNMOC, etc
- 		***Basis for future multi-center ensemble***
**Collaborative effort**
- Broaden research scope -		Enhanced quality
- Share developmental tasks -		Increased efficiency
- Seamless operational suite -		Enhanced product utility
***	******   ******Framework for future technology infusion (MDL, NOAA Labs, Univs.)***

## NORTH AMERICAN ENSEMBLE FORECAST SYSTEM PROJECT

**GOALS:      ****Accelerate improvements in operational weather forecasting**
- 	*through Canadian-US collaboration*
**Seamless (across boundary and in time) suite of products**
- 	*through joint Canadian-US operational ensemble forecast system*
**PARTICIPANTS: ****	****  **Meteorological Service of Canada (CMC, MRB)
- 		  US National Weather Service (NCEP)
**PLANNED ACTIVITIES:  **Ensemble data exchange (June 2004)
- 				   Research and Development -*Statistical post-processing*
*	**	**	*(2003-2007)*	**           -Product development*
*	**	**	**	**	**           **-Verification/Evaluation*
- 				   Operational implementation (2004-2008)
**POTENTIAL PROJECT EXPANSION / LINKS: **
- 		   Shared interest with THORPEX goals of
*	**	**	**Improvements in operational forecasts*
*	**	**	**International collaboration*
- 		   Expand bilateral NAEFS in future
*	**	**	**Entrain broader research community*
*	**	**	**Multi-center / multi-national ensemble system:*
*	**	**	**	**MOA with Japan Meteorological Agency*