# Presentation: 777873

## GEFS and NAEFS Implementation Plan(FY08)

- Yuejian Zhu
- Environmental Modeling Center
- NOAA/NWS/NCEP
- Presented for predictability meeting
- (May 15th 2007)

## Review GEFS Implementation (FY06/07)

- Increase the number of perturbed ensemble members
- 14 (in place of current 10) perturbed runs for each cycle (20 by March 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 configuration

|  | Current | New |
| --- | --- | --- |
| Model | GFS | GFS |
| Initial uncertainty | ETR | ETR |
| 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 | 14 for each cycle | 20 for each cycle |
| Forecast length | 16 days (384 hours) | same |
| Implementation  | May 30th 2006 | March 27th 2007 |

_**GEFS configuration**_

## Review First Implementation of NAEFS

- 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

## Bias Correction Method & Application    

- Bias Correction Method & Application**   **

-  - *b, f, a* represent mean difference, raw forecast and analysis at each grid point (i,j) and each lead-time (t).
*- B* is decaying average bias, w is the weight for the decaying average.
*- F* is bias corrected forecast.
*- w* equals 0.02 (2%) has been used for operation, which is approximately using 50-100 days information

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

## 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
- Reanalysis II initial conditions (T62L28 resolution)
- Enhanced T126/L64 initial conditions by
- Forcing/nudging T126/L64 by large scales from T62/L28 reanalysis (6-hr cycling)
- (Alternate) – upgrade both horizontal and vertical resolution to T190/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 pgrba for NAEFS data exchange.
- About 66 variables for pgrba (51+15)
- 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)

## Current - 2007

**GDAS**

**GFS anal**

**NAM anal**

**CFS**

**RTOFS**

**SREF**

**NAM**

**AQ**

**GFS**

**HUR**

**RDAS**

- Data processing

**Current (2007)**

**GENS/NAEFS**

**Current - 2007**

**NCEP Production Suite**
**Weather, Ocean, Land & Climate Forecast Systems**

## NAEFS Production Suite (current and plan)

- Total allowed: 4:45-6:00 (75m), 46(nodes)*16=736 CPUs

- Current: 4:45-5:17 (32m), 24(nodes)*16=384 CPUs

- Plan (1): increasing vertical resolution from L28 to L64
- Needs: 2.3 factor
- Project: 4:45-6:00 (75m), 23(nodes)*16=368 CPUs

- Plan (2): increasing horizontal resolution from T126 to T190
- Needs: 2.3 factor
- Project: 4:45-6:00 (75m), 50 (nodes)*16=800 CPUs

- Plan (2): real time generation of hind-cast for T126L64
- Needs: 2.3 factor for 26 additional forecasts
- Project: 4:45-6:00 (75m), 50 (nodes)*16=800 CPUs

- alternate

## Why do we need real time hind-cast?

- The factors affecting the quality of forecasts
- Comparing the gain from increasing horizontal resolution
- Reforecast experiments
- Mainly concern the week-two forecast
- Sample size
- Bias correction method
- Statistical reliability
- Updated model
- Considering updated land-surface assimilation

## 500hPa height

- _500hPa height_

- _1000hPa height_

- _2m temperature_

- There is big RMS errors improvement for the first few days. There is no big effect after a short lead-time from these winter season statistics.

## Bias Improvement (absolute value) after Bias correction

- Overall bias reduction:
- (globally)
- D0-3: 50%
- D3-8: 40%
- D8-15: 30%

- _500hPa height_

- _850hPa temperature_

- _Sea level pressure_

- _2m Temperature_

- There is daily variation after bias correction, more bias reduced for valid 12Z cycle

## How many re-forecasts do we really need?

- Note: “years” somewhat misleading, since only 31 days of data
- from each year used in training each day’s regression equation

- _From: Jeff Whitaker and Tom Hamill_

## Skill of CDF correction vs analogs

- Notes: (1) Here, verification on coarse 2.5 degree grid.
- (2) Zhu <CONUS> has benefit at 2.5 mm, correcting drizzle over-forecast.
- (3) Location-dependent Zhu technique using reforecasts adds skill, esp. at 25 mm.
- (4) Large additional skill by using analog reforecast technique, again largest at
- high thresholds.
- (5) The type of calibration technique really matters.

- _From Jeff Whitaker and Tom Hamill_

## MOS 2-M Temp  vs.  Direct Model Output

- Courtesy of Dave Rudack
- _From Kathryn Gilbert_

**Notes:**
Simple technique, but adds skill  This is the most recent study we have looking at direct model output

## Real-time generation of hind-casts

- At T126/L64 resolution
- 4 cycles per day
- T126L64
- Up to 384 hours (16 days)
- Runs
- 28 hind-casts for each cycle starting from 1979
- (option) 7 hind-casts for each cycle starting from 1979
- Initial conditions:
- Atmosphere
- Reanalysis II initial condition (at T62L28 resolution)
- Enhanced T126L64 initial conditions
- Force/nudge T126L64 by large scale info from T62L28 reanalysis
- Generate info on small scales consistent with low resol. reanalysis
- Land-surface
- Reanalysis available soon

## Example of 28 runs per cycle

- Today

- Today+30

- Today-30

- _28 runs per cycle_
- _1979-2007_

- Hind-cast data on-line
- For calibration (61*28)

- _7 runs per cycle_
- _28 runs per day_
- _1979-2007_

- Example of 7 runs per cycle
- Hind-cast data on line
- For calibration (61*7)

- Plan

- Alternate Plan

- 1979

- 1979

## Additional considerations

- Physics upgrade
- Up to 50% increase in CPU?
- Coupled Ocean (MOM4) + Ice ensemble?
- 40% increase
- Extend out to 30-45 days?
- ~100% increase

## Back ground 

## 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_
- (New)

- 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