Progress on FIM development toward membership in the North American Ensemble Forecast System
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Transcript of Progress on FIM development toward membership in the North American Ensemble Forecast System
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Progress on FIM development toward membership in the North
American Ensemble Forecast System
http://fim.noaa.gov
John M. Brown Stan BenjaminRainer Bleck Susan SahmShan Sun Jian-Wen BaoTom Henderson James RosinskiTanya Smirnova Brian Jamison
NOAA-Earth System Research LabBoulder CO
Paper 1c2.2 CMOS 2012 Congress / AMS 21st NWP and 25th WAF Conferences 29 May – 1 Jun 2012
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Flow-following- finite-volume
Icosahedral Model FIM
X-section location
Temp at lowest level
Original concept and early work on FIM was by Sandy MacDonald and Jin Lee, ESRL
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FIM numerical model•Horizontal grid
• Icosahedral, Arakawa A grid – testing 60km/30km/15km•Vertical grid
• Staggered Lorenz grid, ptop = 0.5 hPa, θtop ~2200K• Generalized vertical coordinate
• Hybrid θ-σ option (64L, 38L, 21L options currently)• Hybrid σ-p option (64L, identical to GFS)
•Numerics• Adams-Bashforth 3rd order time differencing• Flux-corrected transport
•Physics• GFS physics suite (May 2011 version, work underway on
Q3FY12 version)•Coupled model extensions
• Chem – WRF-chem/GOCART (Georg Grell)• Ocean – icosahedral HYCOM (Shan Sun 1030 Friday)
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NOAA Earth System Research Laboratory - Boulder, Colorado Page 4
• Finite-volume Integrations on Local Coordinate
• Efficient Indirect Addressing Scheme on Irregular Grid MacDonald, Middlecoff, Henderson, and Lee (2010, IJHPC) : MacDonald, Middlecoff, Henderson, and Lee (2010, IJHPC) : A General Method for Modeling on Irregular Grids.A General Method for Modeling on Irregular Grids.• FIM: Hybrid σ-θ Coordinate
- Bleck, Benjamin, Lee and MacDonald (2010, MWR): On the Use of an Arbitrary Lagrangian-Eulerian Vertical Coordinate in Global Atmospheric Modeling.
• Conservative and Monotonic 3rd-ord Adams-Bashforth w/ FCT Scheme- Lee, Bleck, and MacDonald (2010, JCP): A Multistep Flux-Corrected - Lee, Bleck, and MacDonald (2010, JCP): A Multistep Flux-Corrected Transport SchemeTransport Scheme
• Grid Optimization for Efficiency and Accuracy - Wang and Lee (2011, SIAM): Geometric Properties of Icosahedral-Hexagonal Grid on Sphere.
Novel features of FIM:
Lee and MacDonald (MWR, 2009): A Finite-Volume Icosahedral Shallow Water Model on Local Coordinate.
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Bisection: N=(2**m)*10 + 2 “m” is any integer ratio between arc A-B (~8000 km) and target resolution. e.g., for dx~20 km, then m=8000/20=400N=(400**2)*10+2~1.6 million points.FIM – Ning Wang (ESRL) Can use arbitrary sequence of bisections and trisections
Sadourny, Arakawa, Mintz, MWR (1968)
Construction of an icosahedral grid high granularitypossible with icosahedral model
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The 2-D operator applied to the straight lines, rather than the 3-D operator along the curved lines, e.g.,
Stokes’ theorem:
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Local stereographic projection for each icosahedral grid volume for local geometry
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FIM governing equations and solution procedure
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FIM design – vertical coordinateHybrid (sigma/ isentropic) vertical coordinate Improved transport by reducing numerical dispersion from vertical cross-coordinate transport, improved stratospheric/tropospheric exchange.
• Used in NCEP Rapid Update Cycle (RUC) model
• Used in HYCOM ocean model
Installed as generalized “s” vertical coordinate - can be replaced with GFS sigma-p or other coordinates.
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Staggering of variables in layer or stacked shallow-water models: Used in FIM
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FIM vertical coord hybrid σ-θ-σ option
•2 σ layers at top
•θv reference values for all levels
•σ layers at surface set at max=15 hPa
θ-σ
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(~zero in fixed
grids)
(~zero in material coord.)
(known)
Continuity equation in generalized (“s”) coordinates
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Initial Physics in FIMGFS physics
• Immediate goal for FIM is contributing dynamical-core diversity to NCEP Global Ensemble Forecast System
• Use of current GFS physics (Fanglin Yang’s talk 1B1.2, previous session) allows evaluation of differences between GFS and FIM dynamical cores.
Application of GFS physics to FIM
• No changes needed to physics for hybrid θ-σ application with one exception: mod to avoid negative mass flux in deep/shallow cu, no change to GFS performance
• Applied every 180s (multiple explicit time-steps in FIM)
Current retrospective experiments with Grell-3D replacing GFS deep/shallow cumulus
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Key Recent FIM Changes April 2011
Fix to FCT numerics (error in high-order fluxes) Nov 2011
Upgrade from GFS 2010 physics to May-2011 GFS physics
Addition of icosahedral momentum diffusion (upgraded to 4th order April 2012)
Currently working on upgrade to May 2012 GFS physics (major code upgrade; only minor changes to actual physics)
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Track Error -2011 Atlantic/e.Pacific Tropical Cyclones• GFS oper• FIM30km real-time (EnKF IC)• FIM30km retro (hybrid IC)• FIM15km retro (hybrid IC)
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15
500hPa Height Anomaly Correlation20o – 80o North Latitude, 00UTC only
N = 88 Avg s.d.FIM 87.72 5.05GFS 87.51 5.12
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72h forecasts vs. raobsN. Hemisphere 20-80NFIM vs. GFS
(FIM lower rms errors for V, T, RH at all levels, similar results at 24h,48h)
FIM better
GFS better
FIM better
GFS better FIM
betterGFS better
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Summary• Overall FIM performance roughly equal to
GFS using GFS initial conditions• FIM forecasts often similar to GFS at 5
days, but sometimes quite different.• FIM and GFS “dropouts” often don’t
occur at same initial time• Significant improvement in FIM from 2011
to 2012 (hurricane track errors reduced by 20%)
• Best FIM performance for wind, RH, temp• Less so for heights
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NOAA/ESRL/GSD Assimilation and Modeling Branchpresentations on regional and global NWP
Tue 14:15 Global model (FIM) development (John Brown)
Tue 15:15 Boundary-layer wind simulation in low-level jets (Joe Olson)
Tue 17:30 Gridpoint Statistical Interpolation for Rapid Refresh (Ming Hu)
Wed 16:30 Storm-scale radar-data assimilation (David Dowell)
Wed 17:00 High-Resolution Rapid Refresh climatology (Eric James)
Wed 17:15 GSI cloud analysis and rawinsonde DA (Patrick Hofmann)
Thu 10:45 Rapid Refresh implementation at NCEP (John Brown)
Thu 11:00 High-Resolution Rapid Refresh overview (Curtis Alexander)
Thu 17:30 NWP guidance for a high-impact snowstorm (Ed Szoke)
Fri 10:30 Spatial discretization for global models (Shan Sun)
Fri 17:00 Snow and ice enhancements for RUC LSM (Tanya Smirnova)
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Brief summary of GFS Physics
Radiation: Rapid Radiative Transfer Model for both long and short wave
Surface processes: Noah LSM over land surface fluxes using variable drag coefficient over sea simple sea-ice model
PBL: Han and Pan (NCEP Office Note #464) based on Troen and Mahrt, extra vertical mixing at Sc cloud top if entrainment instability criterion met
Shallow and deep convection: Han and Pan (NCEP Office Note #464) mass flux scheme
Explicit condensate allowed, Zhao and Carr (19xx, MWR) (including simple ice processes)