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Higher Resolution Operational Models

Explore the history and development of major US mesoscale models, including WRF-ARW, NMM-B, COAMPS, MM5, RAMS, and ARPS. Learn about the features, advantages, and applications of each model, as well as their integration in the WRF system infrastructure.

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Higher Resolution Operational Models

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  1. Higher Resolution Operational Models

  2. Major U.S. High-Resolution Mesoscale Models (all non-hydrostatic) • WRF-ARW (developed at NCAR) • NMM-B (developed at NCEP Environmental Modeling Center) • COAMPS (U.S. Navy) • MM5 (NCAR, old, replaced by WRF) • RAMS (Regional Atmospheric Modeling System, Colorado State) • ARPS (Advanced Regional Prediction System): Oklahoma

  3. Operational Mesoscale Model History in US • Early: LFM, NGM (history) • Eta (mainly history) • MM5: Still used by some, but mainly phased out • NMM- Main NWS mesoscale model, updated Eta model. Sometimes called WRF-NMM and NAM. • WRF-ARW: Heavily used by research and some operational communities. • NMM replaced by NMM-B

  4. WRF and NMM

  5. History of WRF model • An attempt to create a national mesoscale prediction system to be used by both operational and research communities. • A new, state-of-the-art model that has good conservation characteristics (e.g., conservation of mass) and good numerics (so not too much numerical diffusion) • A model that could parallelize well on many processors and easy to modify. • Plug-compatible physics to foster improvements in model physics. • Designed for grid spacings of 1-10 km

  6. WRF Software Infrastructure Dynamic Cores Mass Core NMM Core … Static Initialization Post Processors, Verification Obs Data, Analyses 3DVAR Data Assimilation Standard Physics Interface Physics Packages WRF Modeling System

  7. Two WRF Cores • ARW (Advanced Research WRF) • developed at NCAR • Non-hydrostatic Numerical Model (NMM) Core developed at NCEP • Both work under the WRF IO Infrastructure NMM ARW

  8. The NCAR ARW Core Model: (See: www.wrf-model.org) • Terrain following vertical coordinate • two-way nesting, any ratio • Conserves mass, entropy and scalars using up to 6th order spatial differencing equ for fluxes. Very good numerics, less implicit smoothing in numerics. • NCAR physics package (converted from MM5 and Eta), NOAH unified land-surface model, NCEP physics adapted too

  9. NWS NMM1—The NAM RUN • Run every six hours over N. American and adjacent ocean • Run to 84 hours at 12-km grid spacing. • Uses the Grid-Point Statistical Interpolation (GSI) data assimilation system (3DVAR) • Start with GDAS (GFS analysis) as initial first guess at t-12 hour (the start of the analysis cycle) • Runs an intermittent data assimilation cycle every three hours until the initialization time. 1-Non-hydrostatic mesoscale model, NAM: North American Mesoscale run

  10. NMM-B • Hybrid sigma-pressure vertical coordinate • 60 levels • Betts-Miller-Janjic convective parameterization scheme • Mellor-Yamada-Janji boundary layer scheme

  11. NMM-B Details • One-way nested forecasts computed concurrently with the 12-km NMM-B parent run for • CONUS (4 km to 60 hours) • Alaska (6 km to 60 hours) • Hawaii (3 km to 60 hours) • Puerto Rico (3 km to 60 hours) • For fire weather, moveable 1.33-km CONUS and 1.5-km Alaska nests are also run concurrently (to 36 hours). • A change in horizontal grid from Arakawa-E to Arakawa-B grid, which speeds up computations without degrading the forecast

  12. New NAM NEMS based NMMB B-grid replaces E-grid Parent remains 12 km to 84 hr Four Fixed Nests Run to 60 hr 4 km CONUS nest 6 km Alaska nest 3 km HI & PR nests Single placeable 1.33km or 1.5 km FireWeather/IMET/DHS run to 36hr September 2011 NAM-B Upgrade

  13. NMMB 4-km Conus

  14. NAM • Generally less skillful than GFS, even over U.S. • Generally inferior to WRF-ARW at same resolution (more diffusion and smoothing, worse numerics)

  15. Navy COAMPS (Coupled Ocean/Atmosphere Mesoscale Prediction System) • Sigma-Z • Atmosphere And Ocean

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