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Advanced Weather Forecasting Model: Physics Options Overview

This document details advanced physics options for weather forecasting models, including first and second-order diffusion methods, various microphysics schemes, and parameterizations for boundary layer dynamics. Key features include terrain-following coordinates, innovative damping techniques, cloud microphysics variability, and diverse radiation schemes that aid in predicting atmospheric interactions. The aim is to enhance model performance and accuracy through improved algorithmic approaches tailored for both operational and research applications.

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Advanced Weather Forecasting Model: Physics Options Overview

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  1. WRF Physics Options Jimy Dudhia

  2. diff_opt=1 • 2nd order diffusion on model levels • Constant coefficients (khdif and kvdif) • km_opt ignored

  3. diff_opt=2 • 2nd order horizontal diffusion • Allows for terrain-following coordinate • Uses km_opt • 1: constant (khdif and kvdif used) • 2: 1.5-order TKE prediction • 3: Smagorinsky (deformation/stability based K)

  4. damp_opt=1 • Upper level damping layer • Enhanced horizontal and vertical diffusion at top • Cosine function of height • Uses additional parameters • zdamp: depth of damping layer • dampcoef: nondimensional maximum magnitude of damping

  5. mp_physics=1 • Kessler scheme • Warm rain – no ice • Idealized microphysics

  6. mp_physics=2 • Purdue Lin et al. scheme • 5-class microphysics including graupel • 1.2 includes ice sedimentation

  7. mp_physics=3 • NCEP 3-class scheme • From RSM scheme (Hong) • 3-class microphysics with ice • Ice processes below 0 deg C • 1.2 includes ice sedimentation

  8. mp_physics=4 • NCEP 5-class scheme • Also from RSM scheme (Hong) • 5-class microphysics with ice • Supercooled water and snow melt • 1.2 includes ice sedimentation

  9. mp_physics=5 • Ferrier (new Eta) scheme • One prognostic total condensate variable • Diagnostic ice and water species and liquid fractions

  10. mp_physics=99 • Zhao-Carr (old Eta) scheme • Cloud/ice prediction • Diagnostic precipitation evaporation

  11. ra_lw_physics=1 • RRTM scheme from MM5 • Spectral scheme • K-distribution • Look-up table fit to accurate calculations • Interacts with clouds • Ozone from climatology

  12. ra_lw_physics=99 • GFDL longwave scheme used in Eta • Spectral scheme from global model • Also uses tables • Interacts with clouds • Ozone from climatology

  13. ra_sw_physics=1 • MM5 shortwave (Dudhia) • Simple downward calculation • Clear-sky scattering • Water vapor absorption • Cloud albedo and absorption

  14. ra_sw_physics=2 • Goddard shortwave • Spectral method • Interacts with clouds • Ozone effects

  15. ra_sw_physics=99 • GFDL shortwave • Used in Eta model • Ozone effects • Interacts with clouds

  16. bl_sfclay_physics=1 • Monin-Obukhov similarity theory • Taken from standard relations used in MM5 MRF PBL • Provides exchange coefficients to surface (land) scheme • Should be used with bl_pbl_physics=1

  17. bl_sfclay_physics=2 • Monin-Obukhov similarity theory • Modifications due to Janjic • Taken from standard relations used in Eta model, including Zilitinkevich thermal roughness length • Should be used with bl_pbl_physics=2

  18. bl_surface_physics=1 • 5-layer thermal diffusion model from MM5 • Predict ground temp and soil temps • Thermal properties depend on land use • No effect for water • Provides heat and moisture fluxes for PBL

  19. bl_surface_physics=2 • OSU/MM5 Land Surface Model • Vegetation effects included • Predicts soil temperature and soil moisture in four layers • Predicts snow cover and canopy moisture • Diagnoses skin temp • Provides heat and moisture fluxes for PBL

  20. bl_pbl_physics=1 • MRF PBL scheme from MM5 • Non-local mixing in dry convective boundary layer • Depth of PBL determined from critical bulk Ri • Vertical diffusion depends on Ri in free atmosphere

  21. bl_pbl_physics=2 • Mellor-Yamada-Janjic (Eta) PBL • 1.5-order, level 2.5, TKE prediction • Local vertical mixing in boundary layer and free atmosphere

  22. cu_physics=1 • New Kain-Fritsch • As in MM5 and Eta test version • Includes shallow convection • CAPE removal time scale • Mass flux type with updrafts and downdrafts, entrainment and detrainment • Includes cloud detrainment

  23. cu_physics=2 • Betts-Miller-Janjic • As in Eta model • Adjustment type scheme • No explicit updraft or downdraft

  24. cu_physics=99 • Kain-Fritsch • As in MM5 • CAPE removal time scale • Mass flux type with updrafts and downdrafts, entrainment and detrainment • Includes cloud detrainment

  25. Subgrid Turbulence INWORKING ON PLANNED (1) Level 2.5 TKE (2) Level 2 3d Smagorinsky (3) Constant diffusion 2d Smagorinsky (mesoscale)

  26. Microphysics INWORKING ON PLANNED (1) Kessler (2) Lin et al. [Purdue] (3) Cloud3 [NCEP] (4) Cloud5 [NCEP] (5) Eta (Ferrier) (6) Zhao-Carr(old eta) Goddard New Cloud3/5 Lin et al. 2 Reisner 2

  27. Radiation INWORKING ON PLANNED RRTM Eta (GFDL) Goddard Long (1) Dudhia [MM5] (2) Goddard (3) Eta (GFDL) Short

  28. Boundary Layer INWORKING ON PLANNED MRF Mellor-Yamada-Janjic New MRF Boundary layer MRF Similarity Eta Similarity Surface layer 5-layer soil temp OSU/MM5 LSM TGS LSM (RUC) Unified NOAH LSM CLM Land surface

  29. Cumulus INWORKING ON PLANNED New Kain-Fritsch (2) Betts-Miller-Janjic [ETA] (3) Old KF New Grell

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