Post on 01-Apr-2015
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March 2007 NAEFS Upgrade
Yuejian Zhu,
Richard Wobus, Mozheng Wei, Bo Cui and Zoltan Toth
Environmental Modeling Center
NOAA/NWS/NCEP
Acknowledgements:
Qingfu Liu, DingChen Hou, Mark Iredell and Stephen Lord EMC
Luke Lin, David Michaud, Joey Carr and Brent Gordon NCO
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Planned Changes - Summary1. Increasing NAEFS (NCEP/GEFS)
membership• 80 perturbations in cycling (see schematic plot)
• Replaced operational 56 perturbations in cycling
• 20 perturbed long forecasts (16-d) in each cycle• Replaced operational 14 long forecasts in each cycle
2. NAEFS (NCEP/GEFS) post-product• Post-process 20 ensemble forecasts instead of
operational 14 ensemble forecasts for:• Bias correction
• Anomaly forecast
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T00Z
56m
T06Z
56m
T18Z56m
T12Z56m
6hrs Next T00Z
Re-scaling
Re-scaling
Re-scaling
Up to 16-d
Up to 16-d
Up to 16-d
Up to 16-d
T00Z
80m
6hrs
T06Z
80m
T12Z
80m
T18Z
80m
Up to 16-d
Up to 16-d
Up to 16-d
Up to 16-d
Re-scaling
Re-scaling
Re-scaling
Re-scaling
6 hours breeding cycle Production
6 hours breeding cycle Planned Change
Next T00Z
Re-scaling
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Current Plan
Model GFS GFS (current)
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)
00,0612 and 18UTC
same
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 configurations
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Early study indicated:
(by Mozheng Wei)
ET20/80 give most skillful probabilstic forecast when
compared to 10m operation and 10m ET
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Planned Changes 1 • Increasing NAEFS (NCEP/GEFS) membership.
– From current 14 increasing to 20 members per cycle.• Tuning initial perturbations.
• Using 80 cold start initial perturbations (on Jan. 25) – From 24-h forecasts and many dates.
– To have large spread of sampling
– This change is intended to improve ensemble based probabilistic forecast over all and to support NAEFS (North American Ensemble Forecast System) project.
– Results:• Improving probabilistic skills.
• Not much improvement for ensemble mean (expected).
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ENS_s – operationENS_b – large sprdENS_d – small sprd
Doted lines – 1-day spreadDay-5 PAC scores
Doted lines-spread
Cold start from 00UTC Nov. 17 2006
Large initial spread has more skill
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Different period-more runs for large initial spread (cold start)
ENS_s – operationENS_c – large sprd
Cold start from 00UTC Nov. 7th 2007
NH 500hPa ROC
Tropical 500hPa ROC
SH 500hPa ROC
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20m has more prob skills than 14m
ENS_s – operationENS_b – large sprdENS_d – small sprd
NH 500hPa RPSS
SH 500hPa ROC
Tropical 500hPa ROC
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Retrospective experiments/NCO real time parallel
• Retrospective experiments.– Summer period: August 22- September 24 2006 (Hurricane season).
– Winter period: November 7-December 7 2006
– 20 ensemble members.
– Using current GFS.
• NCO real time parallel.– Starting since January 25 2007.
• Full evaluations (follow up above experiments).– Summer: http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/exp/ens_20m_2006_exp_h.html
– Winter: http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/exp/ens_20m_2006_exp_c.html
– NCO real time: http://wwwt.emc.ncep.noaa.gov/gmb/yzhu/html/opr/prx_2007.html
• Expect to implement (March 27 2007).
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Summer 2006Retrospective runs
Winter 2006Retrospective runs
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Summer 2006Retrospective runs
Winter 2006Retrospective runs
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Summer 2006Retrospective runs
Winter 2006Retrospective runs
14
0
50
100
150
200
250
300
12 24 36 48 72 96 120
ENSs ENSx
Hurricane Track Errors (Period: 08/22-09/24/2006)
Cases 157 146 133 121 99 80 58
Hours
ENSs-operational ensembleENSx-retrospective runs
Atlantic Basin
0
100
200
300
400
500
12 24 36 48 72 96 120
ENSs ENSx
Cases 98 86 74 64 40 19 10
East Pacific Basin
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NCO real time parallel
NH 500hPa geopotential height
NCO real time parallel
NH 2 meter temperature
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Conclusions of the 20m experiments• Ensemble mean:
– No significant different (do not expect).– No degradation (not worse – very important)
• Ensemble distribution (probabilistic forecast):– Significant improvement from 20 ensemble members.
• For ROC, EV, Reliability.• Not for RPSS BSS.
• Initial perturbation for cold start: – Large cold start initial spread is (JIFed)
• From backup perturbation based on 24h forecasts in many dates.• Giving sufficient spread in ET.• Quickly scaling down to the expected level (1-2 days).• Able to catch up large uncertainty cases.• Degrading the skills a little for short lead-time in the first few cycles.
– Small cold start initial spread is• From backup perturbation based on 6h forecasts in one day.• No degradation at early cycling.• Not able to catch up large uncertainty system for longer lead-time.• Because error grows very slowly.
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Planned Changes 2Details for Slide 2
• NAEFS (NCEP/GEFS) Post Products– Bias corrected members of joint MSC-NCEP ensemble
• NCEP – Current: 14 (perturbed forecasts) + 1 (control forecast) = 15 forecasts at each cycle– Plan: 20 (perturbed forecasts) + 1 (control forecast) = 21 forecasts at each cycle
• MSC – Same: 16 (multi-model, multi-physics forecasts) + 1 (control forecast) = 17 forecasts at 00UTC and
12UTC cycle only
• 35 of NAEFS variables• Bias correction against each center’s own operational analysis
– Weights for each member for creating joint ensemble (equal weights right now)• 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• NCEP
– Current: 14 (perturbed forecasts) + 1 (control forecast) = 15 forecasts at each cycle– Plan: 20 (perturbed forecasts) + 1 (control forecast) = 21 forecasts at each cycle
• MSC– Same: 16 (multi-model, multi-physics forecasts) + 1 (control forecast) = 17 forecast at 00UTC and
12UTC cycle only
• 19 of NAEFS variables
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NH Mean Sea Level Pressure
NH 2 Meter Temperature
NH 500hPa Height
NCO real time parallel:
Accumulated bias (absolute values) for past one month
Black – raw forecasts
Red – bias corrected forecasts
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Summary of Subjective Analysis• CPC
– We do not see any cause for concern that an increase in the ensemble will have any negative impact on the CPC operational products. Given that, we fully support this implementation to increase the ensemble size.
• HPC– There was little improvement over the standard GFS ensemble forecast. This
subjective evaluation was noted on both mass fields and model QPF. – HOC recommends implementation
• OPC– Little difference noted between operational and parallel data sets.
– OPC recommends implementation
• AWC– While AWC supports the idea to increase the number of members in the
ensemble to represent better the envelope of possibilities for various forecast parameters, we are unable to provide a more rigorous assessment due to the lack of resources to ingest the data and routinely view the available fields