Advanced Research WRF (ARW) Technical Note - MMM - University ...

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1-Way ARW WRF Simulation Two Consecutive ARW simulations (using ndown) 1) Run coarse grid (CG) simulation 2) Process CG for initial condition (IC) for fine grid (FG) 3) Process CG for lateral boundary condition (LBC) for FG 4) Run FG simulation Concurrent ARW simulation with two domains 1) Both CG and FG simulations run within the same WRF 2) FG LBC from CG at each coarse time step 3) CG integrates one time step, then the FG integrates up to the same time 2-Way ARW Simulation Concurrent ARW simulation with two domains Both CG and FG simulations run within the same WRF 2) FG LBC from CG at each coarse time step 3) CG integrates one time step, then the FG integrates up to the same time 4) Feedback FG to CG Figure 7.1: 1-way and 2-way nesting options in the ARW. running two separate simulations with a processing step in between. Also with separate grid simulations, an intermediate re-analysis (such as via 3D-Var, see Section 9) can be used. The second 1-way option (lockstep with no feedback), depicted in the middle box in Fig. 7.1, is run as a traditional simulation with two (or more) grids integrating concurrently, except with the feedback runtime option shut off. This option provides lateral boundary conditions to the fine grid at each coarse grid time step, which is an advantage of the concurrent 1-way method (no feedback). Fine Grid Initialization Options The ARW supports several strategies to refine a coarse-grid simulation with the introduction of a nested grid. When using 1-way and 2-way nesting, several options for initializing the fine grid are provided. • All of the fine grid variables can be interpolated from the coarse grid. • All of the fine grid variables can be input from an external file which has high-resolution information for both the meteorological and the terrestrial fields. • The fine grid can have some of the variables initialized with a high-resolution external data set, while other variables are interpolated from the coarse grid. • For a moving nest, an external orography file may be used to update the fine grid terrain elevation. This option is not generally available in this release. These fine grid initialization settings are user specified at run-time, and the ARW allows nested grids to instantiate and cease during any time that the fine grid’s parent is still integrating. (The 44
1 1 2 2 3 4 3 (a) 1 2 3 x (c) 1 x 2 4 3 Figure 7.2: Various nest configurations for multiple grids. (a) Telescoping nests. (b) Nests at the same level with respect to a parent grid. (c) Overlapping grids: not allowed (d) Inner-most grid has more than one parent grid: not allowed system is currently constrained to starting nests at the beginning of the coarse grid simulations if runs require input of nest-resolution terrain or other lower boundary data. This limitation will be addressed in the near future.) Possible Grid Configurations A simulation involves one outer grid and may contain multiple inner nested grids. In the ARW, each nested region is entirely contained within a single coarser grid, referred to as the parent grid. The finer, nested grids are referred to as child grids. Using this terminology, children are also parents when multiple levels of nesting are used. The fine grids may be telescoped to any depth (i.e., a parent grid may contain one or more child grids, each of which in turn may successively contain one or more child grids; Fig. 7.2a), and several fine grids may share the same parent at the same level of nesting (Fig. 7.2b). Any valid fine grid may either be a static domain or it may be a moving nest with prescribed incremental shifts. The ARW does not permit overlapping grids, where a coarse grid point is contained within more than a single child grid (i.e., both of which are at the same nest level with respect to the parent; Fig. 7.2c). In addition, no grid can have more than a single parent (Fig. 7.2d). For 2-way nested grid simulations, the ratio of the parent horizontal grid distance to the child horizontal grid distance (the spatial refinement ratio) must be an integer. This is also true for the time steps (the temporal refinement ratio). The model does allow the time step refinement ratio to differ from the spatial refinement ratio. Also, nested grids on the same level (i.e., children who have the same parent) may have different spatial and temporal refinement 45 (b) (d)
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NCAR/TN-468+STR NCAR TECHNICAL NOTE
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Contents Acknowledgments ix 1 Intro
Page 5: 8.4.3 Rapid Update Cycle (RUC) Mode
Page 8 and 9: 9.2 Sketch of the role of Stage 0 c
Page 10 and 11: viii
Page 13 and 14: Chapter 1 Introduction The developm
Page 15 and 16: 1.2 Major Features of the ARW Syste
Page 17 and 18: Chapter 2 Governing Equations The A
Page 19 and 20: 2.3 Inclusion of Moisture In formul
Page 21 and 22: the earth. In this formulation we h
Page 23 and 24: Chapter 3 Model Discretization 3.1
Page 25 and 26: and lead to the acoustic time-step
Page 27 and 28: forward step, i.e., step (1) in Fig
Page 29 and 30: { Δy y u i-1/2,j+1 u i-1/2,j v i,j
Page 31 and 32: In the current version of the ARW,
Page 33 and 34: for Cr > 0, and (U t q) i+ 1 2 = U
Page 35 and 36: Chapter 4 Turbulent Mixing and Mode
Page 37 and 38: Symmetry sets the remaining tensor
Page 39 and 40: If ∆x is less than the user-speci
Page 41 and 42: 4.2 Filters for the Time-split RK3
Page 43: where γr is a user specified dampi
Page 46 and 47: exception of the baroclinic wave te
Page 48 and 49: STATIC DATA GRIB DATA SI SYSTEM GRI
Page 50 and 51: 5.2.3 Generating Lateral Boundary D
Page 52 and 53: a boundary on which the condition i
Page 54 and 55: On the coarse grid, the specified b
Page 58 and 59: V V V V U U U U U V V V V V V V
Page 60 and 61: V V V V U U U U U V V V V V V U
Page 62 and 63: coarse grid and fine grid is consis
Page 64 and 65: Table 8.1: Microphysics Options Sch
Page 66 and 67: and it is the water vapor and total
Page 68 and 69: 8.2.2 Betts-Miller-Janjic The Betts
Page 70 and 71: Table 8.3: Land Surface Options Sch
Page 72 and 73: Table 8.5: Radiation Options Scheme
Page 74 and 75: Table 8.6: Physics Interactions. Co
Page 77 and 78: Chapter 9 Variational Data Assimila
Page 79 and 80: supply the following: i) a default
Page 81 and 82: 9.2.4 First Guess at Appropriate Ti
Page 83 and 84: of its useful life. The development
Page 85 and 86: The second stage of gen be (gen be
Page 87: Appendix A Physical Constants The f
Page 90 and 91: Symbols Definition l0 minimum lengt
Page 92 and 93: Subscripts/Superscripts Definition
Page 94 and 95: NWP Numerical Weather Prediction OS
Page 96 and 97: Davies, H. C., and R. E. Turner, 19
Page 98 and 99: Lin, Y.-L., R. D. Farley, and H. D.
Page 100: Walko, R. L., W. R. Cotton, M. P. M
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