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Overview of Major U.S. High-Resolution Mesoscale Models in Operational Meteorology

This document explores the history and evolution of significant high-resolution mesoscale models in the U.S., including WRF-ARW, NMM-B, COAMPS, MM5, RAMS, and ARPS. We detail their development, distinguishing features, and operational use in atmospheric modeling. Notably, WRF-ARW and NMM-B are highlighted for their advancements in numerical techniques and mass conservation. The integration of advanced physics packages and data assimilation methods enhances predictive capabilities, making these models essential for both research and operational meteorology.

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Overview of Major U.S. High-Resolution Mesoscale Models in Operational Meteorology

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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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