Post on 22-Feb-2016
description
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Development of an EnKF/Hybrid Data Assimilation System for Mesoscale Application with the Rapid Refresh
Ming Hu1,2, Yujie Pan3, Kefeng Zhu3, Xuguang Wang3, Ming Xue3,David Dowell1, Steve Weygandt1,
Stan Benjamin1, Jeff Whitaker4, Curtis Alexander1,2
1. Global System Division, ESRL/NOAA, Boulder, CO2. CIRES, University of Colorado, Boulder, CO
3. CAPS, University of Oklahoma, Norman, OK4. Physical Sciences Division, ESRL/NOAA, Boulder, CO
17th conference on IOAS-AOLSAustin, TX 8 January 2013
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Introduction o Rapid Refresh (RAP) is an operational hourly updated
regional numerical weather prediction system for aviation and severe weather forecasting
o GSI-3DVar is used for RAP data assimilationStephen S. Weygandt : Recent Rapid Refresh Enhancements to Improve Forecast Guidance for Aviation Weather Hazards and Improve Initial Fields for High Resolution Rapid Refresh Forecasts. 9.1 in 16th Conference on Aviation, Range, and Aerospace MeteorologyThursday, 10 January 2013: 8:30 AM.
o RAP evolves to a 6-member North American Rapid Refresh Ensemble in the future (2016)
o Testing of an hourly updating EnKF-3DVAR hybrid or EnKF capability for the RAP is underway• OU/CAPS, ESRL, and NCEP/EMC collaboration
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RAP hybrid/EnKF: Benefits
o High-resolution hourly update cyclesSituational Awareness NWP = flow dependent
o For surface and low level weather system• highly localized system• Vertical flow dependence, much needed for good surface
data analysiso For cloud analysis and severe weather
• Anisotropic distribution• Build better situation-dependent balance among T, Q and
cloud variables in analysis increment
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RAP hybrid/EnKF: Challenges
o High-resolution hourly update cycles• Huge computation cost• Short cut-off time: ensemble forecast needs to be
done within a short time• Ensemble convergence fast in hourly analysis
o For surface and low-level weather systems• Ensemble spread is usually poor in low levels
o For cloud analysis and severe weather• Ensemble requires special physical configuration
suitable for cloud and severe weather analysis
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Experiment system 1: RAP Hybrid System using RAP Ensemble
• Same 13km resolution and domain as operation RAP
• Hourly updated cycling with GSI Hybrid (2way) and EnKF
• Cold starts at 03Z May 30, 2012 and continue cycling 3 days
• 40 ensemble members
Using RAP configuration to build an hourly cycling 2-way hybrid system for testing the future implement of the Rapid
Refresh Ensemble
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GSI 3D-VarHMObs
Experiment system 2: RAP GSI hybrid using bkg error cov from GFS Ensemble
GSI 3D-Var
Obs
Cloud Anx
DigitalFilter
HMObs
ReflObs18 hr fcst
GSI 3D-Var
Obs
Cloud Anx
DigitalFilter
1 hr
fcst
HMObs
ReflObs18 hr fcst
Obs
Cloud Anx
DigitalFilter
ReflObs18 hr fcst
13z 14z 15z13 km RAP
1 hr
fcst
current real-time RAP configuration
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GSI HybridHMObs
Experiment system 2: RAP GSI hybrid using bkg error cov from GFS Ensemble
GSI Hybrid
Obs
Cloud Anx
DigitalFilter
HMObs
ReflObs18 hr fcst
GSI Hybrid
Obs
Cloud Anx
DigitalFilter
1 hr
fcst
HMObs
ReflObs18 hr fcst
Obs
Cloud Anx
DigitalFilter
ReflObs18 hr fcst
13z 14z 15z13 km RAP
1 hr
fcst
80 member GFS EnKF Ensemble forecast valid at
15Z (9-h fcst from 6Z)
Available 4 times a day valid at 03, 09, 15, 21Z
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Single observation test for GSI hybrid using bkg error cov from GFS Ensemble
GSI 3D-Var
GSI Hybrid(β=0)
Horizontal cross section of analysis increment from single T obs with 1.0 degree innovation
T
T V
VU
U
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Real-time Test for RAP hybrid using bkg error cov from GFS Ensemble
RMS profile for analysis – soundings from 1000-100mb
o Compare RAP development with GSI hybrid to RAP primary cycle with GSI-Var• Real-time test from Nov 22 to Dec 22, 2012 • GSI hybrid with half static BE and half BE from GFS
Ensemble forecasts
RAP hybrid RAP
TUV RH
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Forecast results: RMS profile
RMS profile for 3-h forecast – soundings from 1000-100mb
RMS profile for 12-h forecast – soundings from 1000-100mb
RAP hybrid RAP
TUV RH
TUV RH
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Forecast results: RMS time series
RAP hybrid RAP
UV RH
TUV
TRMS time series for 12-h forecast – soundings from 1000-100mb
RHRMS time series for 3-h forecast – soundings from 1000-100mb
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Conclusion
o GSI hybrid (using background error covariance from GFS ensemble) is very promising: the statistical results are clearly better than GSI Var• Wind is improved most, next is humidity• Temperature is improved mainly for 3-h but is neutral
for 12-h forecast• Middle to upper-air levels show clear improvement but
low levels are neutralo Successful ensemble forecasts used by GSI hybrid is
key of a successful GSI hybrid analysiso Need to improve RAP hybrid structure
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Future Work
o Tuning parameters• localization, ratio of ensemble BE and static BE, vertical
variance of this ratioo GFS ensemble forecast every 1 h rather than 3 h
• forecast valid at analysis timeo RAP ensemble forecast initialized from GFS EnKF
ensemble• Increase spread in low level• Create WRF special physical fields (such as cloud field)
o North American Rapid Refresh Ensemble by 2016, co-development between ESRL and NCEP/EMC
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Initial Test Results from RAP hybrid (EnKF/var) assimilation (1h, 13km)
RAP hybrid RAP
RMS profile for analysis – soundings from 1000-100mb
T
T
Q
Q
UV
UV
RMS profile for 3-h forecast – soundings from 1000-100mb
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Diagnosis of RAP hybrid using RAP ensemble
Horizontal distribution of Standard Deviation of surface pressure perturbation at 03z, 06z, 09z, 12z, 15z, 18z of May 30, 2012
Time series of prior observation-space ensemble standard deviation 13km
Rapid Refresh