Transcript 452Ensemble.ppt

Ensemble Prediction in the U.S.
NCEP Global Ensemble System
• Begun in 1993 with the MRF (now GFS)
• First tried “lagged” ensembles as basis…using runs
of various initializations verifying at the same time.
• For the last ten years have used the “breeding”
method to find perturbations to the initial conditions
of each ensemble members.
• Breeding adds random perturbations to an initial
state, let them grow, then reduce amplitude down to a
small level, lets them grow again, etc.
• Give an idea of what type of perturbations are
growing rapidly in the period BEFORE the forecast.
• Does not include physics uncertainty.
• Coarse spatial resolution..only for synoptic features.
NCEP Global Ensemble
At 00Z:
• T254L64 high resolution control) out to 7 days, after which
this run gets truncated and is run out to 16 days at a T170L42
resolution
• T62 control that is started with a truncated T170 analysis
• 10 perturbed forecasts each run at T62 horizontal resolution.
The perturbations are from five independent breeding cycle.
At 12Z:
• T254L64 control out to 3 days that gets truncated and run at
T170L42 resolution out to 16 days
• Two pairs of perturbed forecasts based on two independent
breeding cycles (four perturbed integrations out to 16 days.
Major Types of Ensemble
Presentations
NCEP Short-Range Ensembles
(SREF)
• Resolution of 32 km
• Out to 87 h twice a day (09 and 21 UTC
initialization)
• Uses both initial condition uncertainty
(breeding) and physics uncertainty.
• Uses the Eta and Regional Spectral Models
and recently the WRF model (21 total
members)
SREF Current System
Model
RSM-SAS
RSM-RAS
Res (km) Levels Members
45
28 Ctl,n,p
45
28 n,p
Cloud Physics
GFS physics
GFS physics
Convection
Simple Arak-Schubert
Relaxed Arak-Schubert
Betts-Miller-Janjic
BMJ-moist prof
Eta-BMJ
Eta-SAT
32
32
60 Ctl,n,p
60 n,p
Op Ferrier
Op Ferrier
Eta-KF
Eta-KFD
32
32
60 Ctl,n,p
60 n,p
Op Ferrier
Op Ferrier
Kain-Fritsch
Kain-Fritsch
with enhanced
detrainment
PLUS
* NMM-WRF control and 1 pert. Pair
* ARW-WRF control and 1 pert. pair