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NCEP Global Ensemble Forecast System (GEFS)
Yuejian ZhuEnsemble Team Leader
Environmental Modeling CenterNCEP/NWS/NOAAFebruary 20 2014
Current Status (since Feb 2012)• Model
– GFS V9.01 (Spectrum, Euler model) – implemented by May 2011• Horizontal resolution
– T254 (52‐55km for 0‐192 hours), T190 (70‐74km for 192‐384 hours) • Vertical resolution
– 42 hybrid levels– Model top: 2hPa
• Initialization– Breeding‐Vector (BV) and Ensemble Transform with Rescaling (ETR) cycling every 6
hours (80 vectors in cycling)– Tropical Storm Relocation (TSR) since 2005
• Stochastic perturbation– Stochastic Total Tendency Perturbation (STTP) since 2010
• Ensemble size and forecast length– 20 perturbations plus control– 4 cycles per day– Out to 16 days
• Output– Every 6‐hr for 1*1 degree pressure GRIB format files– Full variables for TIGGE data exchange
Next Implementation (Q1FY15)• Model
– GFS V10.0 (Spectrum, Semi‐Lagrangian model) – Plan for Q4FY14• Horizontal resolution
– T574 (T382 physics: 33‐35km for 0‐168 hours), – T382 (T254 physics: 52‐55km for 168‐384 hours)
• Vertical resolution– 64 hybrid levels to match GSI/EnKF hybrid analysis system– Model top: 0.2hPa
• Initialization– Hybrid EnKF f06 and Ensemble Transform with Rescaling (ETR – 3 dimension)– Improved Tropical Storm Relocation (TSR) scheme
• Stochastic perturbation– Stochastic Total Tendency Perturbation (STTP)
• Ensemble size and forecast length– 20 perturbations plus control– 4 cycles per day– Out to 16 days
• Output and data exchange– Every 3‐hr for 0.5*0.5 degree pressure GRIB format files– Full variables for TIGGE data exchange (1*1 degree, every 6‐hr)
Future Plan (end of FY18)• Model
– GFS V11.0 (Spectrum, Semi‐Lagrangian model) – Plan for FY16(?)• Horizontal resolution
– 0‐168hrs – 15‐17km– 168‐336hrs – 33‐35km– 336‐720hrs – 52‐55km
• Vertical resolution– 64 hybrid levels – Model top: 0.2hPa
• Initialization– Hybrid EnKF and ETR – Advanced Tropical Storm Relocation (ATSR)
• Stochastic perturbation– Stochastic Total Tendency Perturbation (STTP)– Various stochastic physical perturbations
• Surface perturbation and coupling– One/two way(s) coupling with ocean model– Perturbed land‐surface model
• Ensemble size and forecast length– 20 (?) perturbations plus control– 4 cycles per day– Out to 30 days
• Real time reforecast– Past 20 years– Once per week (at least)
Additional Information
North American Ensemble Forecast System (NAEFS)
International project to produce operational multi‐center ensemble products
Bias correction and combines global ensemble forecasts from Canada &
USA
Generates products for:Weather forecastersSpecialized users
End users
Operational outlet for THORPEX research using TIGGE archive
StatementThe North American Ensemble Forecast System (NAEFS) combines state of
the art weather forecast tools, called ensemble forecasts, developed at the US National Weather Service (NWS) and the Meteorological Service of Canada (MSC). When combined, these tools (a) provide weather forecast guidance for the 1‐14 day period that is of higher quality than the currently available operational guidance based on either of the two sets of tools separately; and (b) make a set of forecasts that are seamless across the national boundaries over North America, between Mexico and the US, and between the US and Canada. As a first step in the development of the NAEFS system, the two ensemble generating centers, the National Centers for Environmental Prediction (NCEP) of NWS and the Canadian Meteorological Center (CMC) of MSC started exchanging their ensemble forecast data on the operational basis in September 2004. First NAEFS probabilistic products have been implemented at NCEP in February 2006. The enhanced weather forecast products are generated based on the joint ensemble which has been undergone a statistical post‐processing to reduce their systematic errors.
NAEFS Milestones• Implementations
– First NAEFS implementation – bias correction – IOC, May 30 2006 Version 1– NAEFS follow up implementation – CONUS downscaling ‐ December 4 2007 Version 2– Alaska implementation – Alaska downscaling ‐ December 7 2010 Version 3– Implementation for CONUS/Alaska expansion – Q2FY14 Version 4
• Applications of NAEFS Statistical Post‐Processing:– NCEP/GEFS and NAEFS – at NWS– CMC/GEFS and NAEFS – at MSC– FNMOC/GEFS – at NAVY– NCEP/SREF – at NWS
• Publications (or references):– Cui, B., Z. Toth, Y. Zhu, and D. Hou, D. Unger, and S. Beauregard, 2004: “ The Trade‐off in Bias
Correction between Using the Latest Analysis/Modeling System with a Short, versus an Older System with a Long Archive” The First THORPEX International Science Symposium. December 6‐10, 2004, Montréal, Canada, World Meteorological Organization, P281‐284.
– Zhu, Y., and B. Cui, 2006: “GFS bias correction” [Document is available online]– Zhu, Y., B. Cui, and Z. Toth, 2007: “December 2007 upgrade of the NCEP Global Ensemble Forecast
System (NAEFS)” [Document is available online]– Cui, B., Z. Toth, Y. Zhu and D. Hou, 2012: "Bias Correction For Global Ensemble Forecast" Weather and
Forecasting, Vol. 27 396‐410 – Cui, B., Y. Zhu , Z. Toth and D. Hou, 2013: "Development of Statistical Post‐processor for NAEFS”
Weather and Forecasting (In process)– Zhu, Y., and B. Cui, 2007: “December 2007 upgrade of the NCEP Global Ensemble Forecast System
(NAEFS)” [Document is available online]– Zhu, Y, and Y. Luo, 2013: “Precipitation Calibration Based on Frequency Matching Method (FMM)”.
Weather and Forecasting (in process)– Glahn, B., 2013: “A Comparison of Two Methods of Bias Correcting MOS Temperature and Dewpoint
Forecasts” MDL office note, 13‐1
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NCEP CMC NAEFSModel GFS GEM NCEP+CMC
Initial uncertainty ETR EnKF ETR + EnKFModel
uncertainty/StochasticYes (Stochastic Pert) Yes (multi-physics
and stochastic)Yes
Tropical storm Relocation NoneDaily frequency 00,06,12 and 18UTC 00 and 12UTC 00 and 12UTC
Resolution T254L42 (d0-d8)~55kmT190L42 (d8-16)~70km
600*300 (66km)L72
1*1 degree
Control Yes Yes Yes (2)Ensemble members 20 for each cycle 20 for each cycle 40 for each cycle
Forecast length 16 days (384 hours) 16 days (384 hours) 16 daysPost-process Bias correction
(same bias for all members)
Bias correction for each member
Yes
Last implementation February 14th 2012 February 13 2013
NAEFS Current StatusUpdated: February 13 2013
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NUOPC – National Unified Operational Prediction Capability
NUOPC (National Unified Operational Prediction Capability) is an agreement to coordinate activities between the Department of Commerce (National Oceanic and Atmospheric Administration) and the Department of Defense (Oceanographer and Navigator of the Navy and Air Force Directorate of Weather), in order to accelerate the transition of new technology, eliminate unnecessary duplication, and achieve a superior National global prediction capability.
The NUOPC partners determined that the Nation’s global atmospheric modeling capability can be advanced more effectively and efficiently with their mutual cooperation to provide a common infrastructure to perform and support their individual missions.
The NUOPC Tri‐Agency (NOAA, Navy, Air Force) agreed to work on a collaborative vision through coordinated research, transition and operations in order to develop and implement the next‐generation National Operational Global Ensemble modeling system.
NCEP CMC FNMOCModel GFS GEM Global Spectrum
Initial uncertainty ETR EnKF (9) Banded ETModel uncertainty
StochasticYes (STTP) Yes (multi-physics and
Stochastic)None
Tropical storm Relocation None NoneDaily frequency 00,06,12 and 18UTC 00 and 12UTC 00 and 12UTC
Resolution T254L42 (d0-d8)~55kmT190L42 (d8-16)~70km
600*300 (66km)L72
T159L42 ~ 80km
Control Yes Yes NoEnsemble members
20 for each cycle 20 for each cycle 20 for each cycle
Forecast length 16 days (384 hours) 16 days (384 hours) 16 days (384 hours)Post-process Bias correction for
ensemble meanBias correction for
each memberBias correction for
member meanLast
implementation February 14 2012 February 13 2013 NAVGEM
implementation on February 13 2013
NUOPC Current StatusUpdated: February 13 2013
10‐day forecast
Northern Hemisphere 500hPa height:
30‐day running mean scores of day‐10 CRPS skill scoreRMS error and ratio of RMS error / spreadAnomaly correlation
All other regions could be seen from: http://www.emc.ncep.noaa.gov/gmb/yluo/naefs/VRFY_STATS/T30_P500HGT
AC score CRPS
RMS error