# Presentation: 819421

## Global Ensemble and NAEFS

- Yuejian Zhu and Zoltan Toth
- Environmental Modeling Center
- NOAA/NWS/NCEP
- Acknowledgements:
- R. Wobus, M. Wei, B. Cui, D. Hou, M. Iredell and S. J. Lord  ***EMC***
- B. Gorden, S. Jacobs and D. Michaud  ***NCO***
- E. Olenic, D. Unger and D. Collins ***CPC***
- Presentation for 3rd Ensemble User Workshop
- October 31st 2006

## Outlines

- NAEFS History and Milestones
- GEFS, NAEFS and THORPEX
- Review GEFS Implementation (FY06)
- Review First NAEFS Implementation (FY06)
- Ensemble Products and Functionalities
- Ensemble Data Request Information
- GEFS Major Implementation Plan (FY07)
- NAEFS Upgrade Plan (FY07)
- NAEFS Expansion and Future Plan

## NAEFS History and Milestones

- February 2003, Long Beach, CA
- NOAA / MSC high level agreement about joint ensemble research/development work
- (J. Hayes, L. Uccellini, D. Rogers, M. Beland, P. Dubreuil, J. Abraham)
- May 2003, Montreal (MSC)
- 1st NAEFS Workshop, planning started
- November 2003, MSC & NWS
- 1st draft of NAEFS Research, Development & Implementation Plan complete
- May 2004, Camp Springs, MD (NCEP)
- Executive Review
- September 2004, MSC & NWS
- Initial Operational Capability implemented at MSC & NWS
- November 2004, Camp Springs
***Inauguration ceremony & 2******nd****** NAEFS Workshop***
- Leaders of NMS of Canada, Mexico, USA signed memorandum
- 50 scientists from 5 countries & 8 agencies
- May 2006, MSC & NWS
- 1st Operational Implementation
- Bias correction
- Climate anomaly forecasts
- June 2006, Montreal (MSC)
- 3rd NAEFS Workshop
- March 2007, 2008, MSC, NWS
- Follow-up implementations-Improved and expanded product suite

## GEFS, NAEFS and THORPEX

- NCEP Global Ensemble Forecast System (GEFS) is part of NAEFS
- NAEFS is combining NCEP and CMC global ensemble
- THORPEX is the research project:
- Provides framework for transitioning research into operations
- Prototype for ensemble component of THORPEX legacy forecast system:
***            ******Global Interactive Forecast System (GIFS)***

**THORPEX Interactive Grand**
**Global Ensemble (TIGGE)**

**North American Ensemble**
**Forecast System (NAEFS)**

*OPERATIONS*

*RESEARCH*

*Articulates*
*operational needs*

*Transfers*
*New methods*

- THORPEX

- RESEARCH

- LEGACY (GIFS)

- OPERATIONAL

## Review GEFS Implementation (FY06)

- Increase the number of perturbed ensemble members
- 14 (in place of current 10) perturbed runs for each cycle (20 by early 2007)
- NAEFS requirement
- This change is intended to improve ensemble based prob. forecasts
- Results: improved probabilistic skill, slightly improved ensemble mean skill (seasonally dependent)
- Add control runs for 06, 12 and 18Z cycles
- This change is intended to enable for relocation of perturbed tropical storm
- Facilitates comparison of high & lower resolution ensemble controls
- If lores control and ensemble mean differ – indication of nonlinearities
- If high & lores controls differ – indication for possible effect of resolution
- Introduce Ensemble Transform (ET) into GEFS breeding method
- ET breeding method creates globally orthogonal initial perturbations
- Uses simplex method to create individual (not paired) perturbations
- This change is intended to improve probabilistic forecast skill
- Results: Improved probabilistic forecast skill; Slightly reduced ensemble mean hurricane track errors for 12-96 hours
- Changes of File Names and Structures

## GEFS configurations

|  | Current | Plan |
| --- | --- | --- |
| Model | GFS | GFS |
| Initial uncertainty | BV | ETBV |
| Model uncertainty | None | None |
| Tropical storm | Relocation | same |
| Daily frequency | 00,06,12 and 18UTC | same |
| Hi-re control 
(GFS) | T382L64 (d0-d7.5)
T190L64 (d7.5-d16) | same |
| Low-re control (ensemble control) | T126L28 (d0-d16)
00UTC only | T126L28 (d0-d16)
00,06,12 and 18UTC |
| Perturbed members | 10 for each cycle | 14 (20) for each cycle |
| Forecast length | 16 days (384 hours) | same |
| Implementation  | August 17th 2005 | May 30th 2006 |

_**GEFS configurations**_

## Ensemble Transform Bred Vector

- P1

- N1

- P2

- N2

- P#, N# are the pairs of positive and negative
- P1 and P2 are independent vectors
- Simple scaling down (no direction change)

- _Ensemble Transform Bred Vector_
- (Plan)

- P1, P2, P3, P4 are orthogonal vectors
- No pairs any more
- To centralize all perturbed vectors (sum of all vectors are equal to zero)
- Scaling down by applying mask,
- The direction of vectors will be tuned by ET.

- _Rescaling_

**ANL**

**ANL**

**ANL**

- _Bred Vector_
- (Current)

_**P1 forecast**_

_**P4 forecast**_

_**P3 forecast**_

_**P2 forecast**_

- t=t1

- t=t0

- t=t0

- t=t2

- t=t2

- t=t1

- _Rescaling_

## Changes of File Names and Structures

- Pressure GRIB Files Split into Two
- Pgrba – 51 Variables For NAEFS Exchange
- Pgrbb – Remaining 278 Variables
- Perturbation runs from pairs to single size
- P1, n1, p2, n2 ... convert to p0, p02, p03, p04 ...
- Enspost.* and Ensemble.* Files Eliminated
- Data Was Duplicate to Pressure GRIB Data Packed in Different Format
- Ensemble Extensions Corrected in Pressure GRIB Files
- 6-Hourly Precipitation/Max/Min Accumulations Available in Pressure GRIB Files
- GEMPAK Files Created for NAEFS Members for Raw and Bias Corrected pgrba Files
- GEMPAK Metafiles For HPC Medium Range Desk Created in Production

## Review First NAEFS Implementation (FY06)

- Bias corrected members of joint MSC-NCEP ensemble
- Decaying accumulated bias (~past 50 days) for each var. for each grid point
- For selected 35 of 50 NAEFS variables
- 32(00Z), 15(06Z), 32(12Z) and 15(18Z) joint ensemble members
- Bias correction against each center’s own operational analysis
- Weights for each member for creating joint ensemble (equal weights now – unequal weights to be added later)
- Weights don’t depend on the variables
- Weights depend on geographical location (low precision packing)
- Weights depend on the lead time
- Climate anomaly percentiles for each member
- Based on NCEP/NCAR 40-year reanalysis
- Used first 4 Fourier modes for daily mean,
- Estimated climate pdf distribution (standard deviation) from daily mean
- For selected 19 of 50 NAEFS variables
- 32(00Z), 15(06Z), 32(12Z) and 15(18Z) joint ensemble members
- Adjustment made to account for difference between oper. & re-analysis
- Provides basis for downscaling if local climatology available
- Non-dimensional unit

## Schematic diagram for forecast anomalies

- _Climatology_

- _Bias-corrected_
- _Ensemble forecast_

- Temperature

- _Medium forecast (50%)_

- _Lower extreme_
- (10%)

- _Upper extreme_
- (90%)

- _Modified climatology_

- _Ensemble forecast_

- _Clmatology is generated from NCEP/NCAR reanalysis_
- _(40 years from 1958 to 1997)_

## Example of probabilistic forecast in terms of climatology

- ENSEMBLE 10-, 50- (MEDIAN) & 90-PERCENTILE FORECAST VALUES (BLACK CONTOURS) AND CORRESPONDING CLIMATE PERCENTILES (SHADES OF COLOR)

## Ensemble Product Request List

- NCEP SERVICE CENTERS, OTHER PROJECTS

## Ensemble Functionalities

|  | FUNCTIONALITY | CENTRALLY GENERATED | LOCALLY GENERATED | INTERACTIVE
ACCESS |
| --- | --- | --- | --- | --- |
| 1 | Mean of selected members  Done |  |  |  |
| 2 | Spread of selected members Done  |  |  |  |
| 3 | Median of selected values Done Sept. 2005 |  |  |  |
| 4 | Lowest value in selected members Done Sept. 2005 |  |  |  |
| 5 | Highest value in selected members Done Sept. 2005 |  |  |  |
| 6 | Range between lowest and highest values Done Sept. 2005 |  |  |  |
| 7 | Univariate exceedance probabilities for a selectable threshold value Done, Dec 05 |  |  |  |
| 8 | Multivariate (up to 5) exceedance probabilities for a selectable threshold value Done, Dec 05 |  |  |  |
| 9 | Forecast value associated with selected univariate percentile value Done Sept. 2005 |  |  |  |
| 10 | Tracking center of maxima or minima in a gridded field (eg – low pressure centers) Done Sept. 2005 |  |  |  |
| 11 | Objective grouping of members Planning starts FY06, Deliver FY07-08 |  |  |  |
| 12 | Plot Frequency / Fitted probability density function at selected location/time (lower priority) Detailed Planning FY06, Deliver FY07 |  |  |  |
| 13 | Plot Frequency / Fitted probability density as a function of forecast lead time, at selected location (lower priority) Detailed Planning FY06, Deliver FY07 |  |  |  |
| 14 | Spaghetti (ability to interactively change contour/domain etc)  Basic function done; Interactive version to be scheduled (TBS) |  |  |  |

- List of centrally/locally/interactively generated products required by NCEP Service Centers for each functionality are provided in attached tables (eg., *MSLP, Z,T,U,V,RH, etc, at 925,850,700,500, 400, 300, 250, 100, etc hPa)*

***Potentially useful functionalities that need further development:***
- - Mean/Spread/Median/Ranges for amplitude of specific features *(TBS)*- Mean/Spread/Median/Ranges for phase of specific features *(TBS)*

***Additional basic GUI functionalities:**** *- Ability to manually select/identify members *(TBS)*
- - Ability to weight selected members *Done, Sept. 05*

## Ensemble Data Request Information

- AT NCDC : Over 10 days, 09/26-10/05 0026    meteo.noa.gr 0003    dip0.t-ipconnect.de 1527    weathersa.co.za 1860    fsu.edu
- In a ten day period 09/26-10/05 0001    retail.telecomitalia.it 0001    196.12.132.227 0001    rr.com 0002    proxy2.enpc.fr 0003    202.131.2.222 0065    fi.upm.es 0071    bruneiweather.com.bn 0150    abo.wanadoo.fr 0152    meteo.noa.gr 0297    zedxinc.com 0968    buran.meteotest.ch 1050    nps.edu 1141    nuvox.net 1298    sd.cesga.es 1927    live-servers.net 9489    psu.edu 137069    cox.net

## Ensemble Data Request Information (Cont.)

- A list of the users who pulled GEFS data from the NCEP anonymous ftp server in September, and have left a valid email address at login.
- 26 e-mail lists
- A list of the users who pulled GEFS data from the WOC server in the past month, and have left a valid email address at login.
- 26 e-mail lists.

## Ensemble Web-Page Access Information

**Usage Statistics for GMB ENS www.emc.ncep.noaa.gov**
**Summary Period: Last 12 Months****Generated 30-Oct-2006 14:30 EST**

## GEFS Major Implementation Plan (FY07)

- Upgrade vertical resolution from 28 to 64 levels for 20 perturbed forecasts
- 4 cycles per day
- T126L64
- Up to 384 hours (16 days)
- Real-time generation of hind-cast at T126/L64 resolution.
- 4 cycles per day
- 27 hind-casts for each cycle since 1979
- Using reanalysis II initial conditions (T62L28 resolution)
- Add random noise to high frequency (T63-T170) by using
- Cycling (6-hr T170 model forecast)
- Other method?
- (Alternate) – upgrade both horizontal and vertical resolution to T170/L64
- Introduce ESMF scheme that allows concurrent generation of all ensemble members.
- Add stochastic perturbation scheme to account for model errors (tentative plan)

## NAEFS upgrade plan (FY07)

- Add approximately 15 new variables to current 51 pgrba for NAEFS data exchange.
- Such as vertical shear, helicity, u,v, t, RH for 100, 50hPa, LH, SWR, LWR at surface, and etc..
- Add GFS high resolution control bias correction by using current method for ensemble.
- There is a problem when we estimate bias after GFS change resolution after 180 hours
- Set up GFS low resolution (ensemble) control run on NCO’s real time parallel prior to GFS upgrade in the future.
- As bias estimation of GFS major/minor implementation
- Need to compare the bias of ensemble mean and control
- Improve bias correction algorithm.
- Pending on hind-cast information
- Two weights: one from real-time (analysis and forecast) bias estimation (mainly for week-1), another one from hind-cast (mainly for week-2)

## NAEFS Expansion and Future Plan

- Plans to be coordinated with THORPEX
- Links with Phase-2 TIGGE archive and beyond (GIFS)
- Expansion
- FNMOC
- Experimental data exchange by Dec 2006
- Preliminary evaluation by Dec 07
- Operational implementation by Dec 08 (subject to improved performance)
- UK Metoffice
- Decision on going operational & possibly joining NAEFS - by 2008
- KMA, CMA, JMA
- Expressed interest, no detailed plans yet
- Data exchange with MSC
- Replace current ftp with more reliable telecom by Dec 08
- Statistical post-processing
- Continual enhancements to current methods (2nd moment correction, addtnl vars)
- Testing (Dec 08) & possible implementation (09) of advanced methods
- Products
- Week-2 – experimental by Nov 06
- Web graphics
- MSC – Nov 06
- NCEP – Mar 07

## Background !!!!!

## Bias Correction Method & Application    

-  decaying averaging mean error = (1-*w*) * prior t.m.e + *w* * (f – a)

-   Bias Correction: application to NCEP operational ensemble 15 members

- Bias Correction Method & Application**   **

- 6.6%

- 3.3%

- 1.6%

*For separated cycles**, **each lead time and individual grid point, t.m.e = time mean error*

-  Test different decaying weights.
-    0.25%, 0.5%, 1%, 2%, 5% and
-    10%, respectively
-   Decide to use 2% (~ 50 days)
-    decaying accumulation bias
-    estimation

*Toth, Z., and Y. Zhu, 2001*

## List of Variables for Bias Correction, Weightsand Forecast Anomalies for CMC & NCEP Ensemble

## Recently Statistics

_**Recently Statistics**_

## Based on raw forecasts, no climate and current analysis correction