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- 1. WIND ENERGY METEOROLOGY UNIT 6 ATMOSPHERIC FLOW MODELING II: MESO-SCALE MODELING Detlev Heinemann ENERGY METEOROLOGY GROUP INSTITUTE OF PHYSICS OLDENBURG UNIVERSITY FORWIND – CENTER FOR WIND ENERGY RESEARCHMittwoch, 15. Juni 2011
- 2. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION ‣ The atmosphere features a wide range of circulation types, with a wide variety of different behaviors. ‣ Typically, these circulations are classified according to their size (spatial scale) and/or their oscillation period or duration (time scale) 2Mittwoch, 15. Juni 2011
- 3. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION Scale Category Time Scale Spatial Scale Examples seconds to turbulence, small microscale meters to 1 km minutes cumulus clouds thunderstorms, sea minutes to hours kilometers to mesoscale breezes, mountain to 1 day hundreds of km circulations fronts, cyclones, synoptic scale days to weeks thousands of km anticyclones planetary waves, planetary scale weeks to months global el niño 3Mittwoch, 15. Juni 2011
- 4. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION EXAMPLE: MICROSCALE boundary layer turbulence small cumulus clouds / turbulent eddies 4Mittwoch, 15. Juni 2011
- 5. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION EXAMPLE: MESOSCALE thunderstorms/collections of individual storms and their thunderstorms component parts 5Mittwoch, 15. Juni 2011
- 6. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION EXAMPLE: MESOSCALE mountain circulations (lee vortices in this case) 6Mittwoch, 15. Juni 2011
- 7. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION EXAMPLE: MESOSCALE sea breeze circulations 7Mittwoch, 15. Juni 2011
- 8. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION EXAMPLE: SYNOPTIC SCALE high and low pressure most of what we consider day-to- systems, warm and cold fronts day weather 8Mittwoch, 15. Juni 2011
- 9. ATMOSPHERIC FLOW MODELING II SCALES OF ATMOSPHERIC MOTION EXAMPLE: GLOBAL SCALE planetary-scale waves climate patterns (e.g., el niño / la niña) 9Mittwoch, 15. Juni 2011
- 10. ATMOSPHERIC FLOW MODELING II MESOSCALE MODELING EXAMPLE: WEATHER RESEARCH & FORECASTING MODEL (WRF) http://www.wrf-model.org 10Mittwoch, 15. Juni 2011
- 11. ATMOSPHERIC FLOW MODELING II WHAT IS WRF...? ‣ Weather Research and Forecasting Model ‣ Operational forecasting and atmospheric research ‣ Community Model ‣ Developed by NCAR and NOAA ‣ New Version – 3.3: released April 2011 11Mittwoch, 15. Juni 2011
- 12. ATMOSPHERIC FLOW MODELING II WHAT IS WRF...? WRF system components 12Mittwoch, 15. Juni 2011
- 13. ATMOSPHERIC FLOW MODELING II WHAT IS WRF...? ‣ Non-hydrostatic model ‣ Terrain-following hydrostatic pressure coordinate ‣ Arakawa C-grid staggering ‣ Runge-Kutta 2nd and 3rd order time integration schemes ‣ 2nd to 6th order advection schemes ‣ Semi-implicit acoustic step off-centering ‣ ARW and NMM dynamical cores. 13Mittwoch, 15. Juni 2011
- 14. ATMOSPHERIC FLOW MODELING II WHAT IS WRF...? ‣ Advanced Research WRF (ARW) and Nonhydrostatic Mesoscale Model (NMM) are both dynamical cores ‣ Dynamical core includes advection, pressure- gradients, Coriolis, buoyancy, filters, diffusion and time-stepping. ‣ Both use Eulerian mass dynamical cores with terrain-following vertical coordinates ‣ Both share physics, software framework, and parts of the pre- and post-processing systems. 14Mittwoch, 15. Juni 2011
- 15. ATMOSPHERIC FLOW MODELING II ARW OR NMM...? ‣ ARW and NMM ‣ Atmospheric physics research ‣ Case-study research ‣ Real-time NWP and forecast system research ‣ Data assimilation research ‣ Teaching dynamics and NWP ‣ ARW only ‣ Regional climate and seasonal time-scale research ‣ Coupled-chemistry applications ‣ Global simulations ‣ Idealized simulations at many scales (e.g. convection, baroclinic waves, large eddy simulations) 15Mittwoch, 15. Juni 2011
- 16. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: KEY FEATURES ‣ Equations ‣ Fully compressible ‣ Non-hydrostatic ‣ Scalar conservative ‣ Vertical Coordinate ‣ Mass-based terrain following coordinate ‣ Top of model is a constant pressure surface 16Mittwoch, 15. Juni 2011
- 17. ATMOSPHERIC FLOW MODELING II GOVERNING EQUATIONS compressible, nonhydrostatic, flux-form Euler equations (using a terrain-following mass vertical coordinate) plus diagnostic relation for the inverse density equation of state (plus inclusion of moisture...) 17Mittwoch, 15. Juni 2011
- 18. ATMOSPHERIC FLOW MODELING II VERTICAL COORDINATE The ARW equations are formulated using a terrain-following hydrostatic-pressure vertical co- ordinate denoted by η and defined as where where ph: hydrostatic component of the pressure phs and pht: values along the surface and top boundaries, respectively. η varies from a value of 1 at the surface to 0 at the upper boundary of the model domain. This vertical coordinate is also called a mass vertical coordinate. 18Mittwoch, 15. Juni 2011
- 19. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: KEY FEATURES Horizontal grid Arakawa C-grid staggering 19Mittwoch, 15. Juni 2011
- 20. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: KEY FEATURES ‣ Prognostic Variables ‣ Velocity componets u, v ‣ Vertical velocity w, potential temp, geopotential, surface pressure ‣ Time Integration ‣ 3rd order Runge-Kutta scheme (Wicker and Skamarock, 2002) Defining the prognostic variables in the ARW solver as Φ = (U, V, W, Θ, φ′, µ′, Qm) and the model equations as Φt = R(Φ), the RK3 integration takes the form of 3 steps to advance a solution Φ(t) to Φ(t + ∆t): 20Mittwoch, 15. Juni 2011
- 21. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: KEY FEATURES ‣ Spatial Discretization ‣ 2nd to 6th order advection options in horizontal and vertical ‣ Turbulent Mixing and Model Filters ‣ Divergence damping, sub-grid scale turbulence formulation ‣ Initial Conditions ‣ 3 dimensional for real cases ‣ Digital filtering initialization (DFI) 21Mittwoch, 15. Juni 2011
- 22. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: KEY FEATURES ‣ Lateral Boundary Conditions ‣ Periodic, open, symmetric ‣ Top Boundary Conditions ‣ Gravity wave absorbing ‣ Constant pressure level ‣ Rigid lid option ‣ Bottom Boundary Conditions ‣ Physical or free-slip 22Mittwoch, 15. Juni 2011
- 23. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: KEY FEATURES ‣ Earths rotation ‣ Full Coriolis terms included ‣ Mapping to Sphere ‣ Four supported map projections ‣ Nesting ‣ One-way and two-way nesting ‣ Static or moving grids ‣ Nudging ‣ Grid analysis and observation nudging capabilities 23Mittwoch, 15. Juni 2011
- 24. ATMOSPHERIC FLOW MODELING II WRF MODEL PHYSICS ‣ Microphysics: Bulk schemes ranging from simplified physics suitable for mesoscale modeling to sophisticated mixed-phase physics suitable for cloud-resolving modeling. ‣ Cumulus parameterizations: Adjustment and mass-flux schemes for mesoscale modeling in- cluding NWP. ‣ Surface physics: Multi-layer land surface models ranging from a simple thermal model to full vegetation and soil moisture models, including snow cover and sea ice. ‣ Planetary boundary layer physics: Turbulent kinetic energy prediction or non-local K schemes. ‣ Atmospheric radiation physics: Longwave and shortwave schemes with multiple spectral bands and a simple shortwave scheme. Cloud effects and surface fluxes are included. 24Mittwoch, 15. Juni 2011
- 25. ATMOSPHERIC FLOW MODELING II WRF MODELING SYSTEM 25Mittwoch, 15. Juni 2011
- 26. ATMOSPHERIC FLOW MODELING II WRF PRE-PROCESSING SYSTEM ‣ The purpose of the WPS is to prepare input to WRF for real- data simulations. It: ‣ defines simulation domain and ARW nested domains ‣ computes latitude, longitude, map scale factor and Coriolis parameters at every grid point ‣ interpolates time invariant terrestrial data to simulation grids (e.g. terrain height and soil type) ‣ interpolates time-varying meteorological fields from another model onto simulation domains 26Mittwoch, 15. Juni 2011
- 27. ATMOSPHERIC FLOW MODELING II WRF PRE-PROCESSING SYSTEM 27Mittwoch, 15. Juni 2011
- 28. ATMOSPHERIC FLOW MODELING II THE GEOGRID PROGRAM ‣ Geogrid defines ‣ Map projection ‣ Geographic location of domains ‣ Dimensions of domain ‣ Geogrid provides ‣ Values for static fields at each model grid point ‣ Computes latitude, longitude, map scale factor and Coriolis parameters at each grid point ‣ Horizontally interpolates static terrestrial data (e.g. topography, height, land use category, soil type, vegetation fraction, monthly surface albedo) 28Mittwoch, 15. Juni 2011
- 29. ATMOSPHERIC FLOW MODELING II THE GEOGRID PROGRAM ‣ First, choose a map projection ‣ Why? - The Earth is roughly ellipsoidal, but WRF computational domains are defined by rectangles on a plane ‣ ARW can use the following projections ‣ Lambert conformal ‣ Mercator ‣ Polar stereographic ‣ Latitude-longitude 29Mittwoch, 15. Juni 2011
- 30. ATMOSPHERIC FLOW MODELING II ARW PROJECTIONS 30Mittwoch, 15. Juni 2011
- 31. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: NESTING ‣ A nested domain is wholly contained within its parent domain and receives information from its parent. ‣ It may also feed information back to its parent [2-way nesting] ‣ A nested domain has exactly one parent ‣ A domain may have one or more children ‣ 2-way nests on the same nesting level must not overlap in coverage 31Mittwoch, 15. Juni 2011
- 32. ATMOSPHERIC FLOW MODELING II ARW DYNAMICS: NESTING Nesting structure as a tree for the domains at left Example configuration: 4 domains Each domain is assigned a domain ID # 32Mittwoch, 15. Juni 2011
- 33. ATMOSPHERIC FLOW MODELING II GEOGRID: INTERPOLATING STATIC FIELDS ‣ Geogrid interpolates terrestrial, time-invariant fields ‣ Topography height ‣ Land use categories ‣ Soil type (top layer and bottom layer) ‣ Annual mean soil temperature ‣ Monthly vegetation fraction ‣ Monthly surface albedo 33Mittwoch, 15. Juni 2011
- 34. ATMOSPHERIC FLOW MODELING II GEOGRID: INTERPOLATING STATIC FIELDS Normally, source data are given on a different projection from the model grid 34Mittwoch, 15. Juni 2011
- 35. ATMOSPHERIC FLOW MODELING II GEOGRID: INTERPOLATING STATIC FIELDS ‣ Interpolation options ‣ 4-point bilinear ‣ 16-point overlapping parabolic ‣ 4-point average (simple or weighted) ‣ 16-point average (simple or weighted) ‣ Grid cell average ‣ Nearest neighbour ‣ Breadth-first search 35Mittwoch, 15. Juni 2011
- 36. ATMOSPHERIC FLOW MODELING II WRF PRE-PROCESSING SYSTEM 36Mittwoch, 15. Juni 2011
- 37. ATMOSPHERIC FLOW MODELING II THE UNGRIB PROGRAM ‣ What is a GRIB file? ‣ WMO standard file format for storing regulary distributed fields ‣ General Regularly-distributed Information in Binary ‣ Fields are compressed with a lossy compression [Think of truncating numbers to a fixed number of digits] ‣ Fields in file are identified by code number ‣ These numbers are referenced against an external table to determing the corresponding field 37Mittwoch, 15. Juni 2011
- 38. ATMOSPHERIC FLOW MODELING II THE UNGRIB PROGRAM ‣ What does it do? ‣ reads in GRIB data ‣ extracts meteorological fields ‣ derives required fields if necessary ‣ e.g. Computes RH from T, P and Q ‣ writes requested fields to an intermediate file format ‣ How does ungrib know which fields to extract? ‣ from vtables ... 38Mittwoch, 15. Juni 2011
- 39. ATMOSPHERIC FLOW MODELING II THE UNGRIB PROGRAM: VTABLES 39Mittwoch, 15. Juni 2011
- 40. ATMOSPHERIC FLOW MODELING II WRF PRE-PROCESSING SYSTEM 40Mittwoch, 15. Juni 2011
- 41. ATMOSPHERIC FLOW MODELING II THE METGRID PROGRAM ‣ Horizontally interpolates meteorological data, extracted by ungrib, to simulation domains, defined by geogrid ‣ Rotates winds to WRF grid ‣ i.e. rotates so that U-component is parallel to x-axis, V- component parallel to y-axis 41Mittwoch, 15. Juni 2011
- 42. ATMOSPHERIC FLOW MODELING II WPS SUMMARY 42Mittwoch, 15. Juni 2011
- 43. ATMOSPHERIC FLOW MODELING II INITIALIZATION ‣ ideal.exe ‣ Program for controlled (idealized) scenarios ‣ Examples include 2-D and 3-D idealized cases, with or without topography, with or without an initial thermal perturbation. ‣ real.exe ‣ Program for real data cases ‣ Interpolates the intermediate files generated by metgrid.exe in the vertical, creates boundary and initial condition files and does some consistency checks. 43Mittwoch, 15. Juni 2011
- 44. ATMOSPHERIC FLOW MODELING II RUNNING WRF ‣ ideal.exe ‣ Program for controlled (idealized) scenarios ‣ Examples include 2-D and 3-D idealized cases, with or without topography, with or without an initial thermal perturbation. ‣ real.exe ‣ Program for real data cases ‣ Interpolates the intermediate files generated by metgrid.exe in the vertical, creates boundary and initial condition files and does some consistency checks. 44Mittwoch, 15. Juni 2011
- 45. ATMOSPHERIC FLOW MODELING II POST-PROCESSING: GRAPHICS ‣ Several graphical packages available ‣ NCL ‣ ARWpost ‣ RIP4 ‣ VAPOR ‣ IDV 45Mittwoch, 15. Juni 2011
- 46. ATMOSPHERIC FLOW MODELING II POST-PROCESSING: GRAPHICS NCL graphis ‣ NCAR Command Language ‣ reads in WRF-ARW data directly ‣ generates a number of graphical plots using scripts ‣ e.g. Horizontal, cross- section, skewT, meteogram, panel 46Mittwoch, 15. Juni 2011
- 47. ATMOSPHERIC FLOW MODELING II POST-PROCESSING: VERIFICATION MET verification software ‣ Model Evaluation Tools ‣ All the basics – RMSE, bias, skill scores ‣ Advanced spatial methods (wavelets, objects) ‣ Confidence intervals 47Mittwoch, 15. Juni 2011

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