WRF Post-Processing Wei Wang and Bill Skamarock NCAR/MMM Ethan Alpert (NCAR/SCD)
WRF Project Overview Joseph B. Klemp, NCAR COMET WORKSHOP Boulder, Colorado 31 March 2000
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Transcript of WRF Project Overview Joseph B. Klemp, NCAR COMET WORKSHOP Boulder, Colorado 31 March 2000
WRF Project Overview
Joseph B. Klemp, NCAR
COMET WORKSHOP
Boulder, Colorado
31 March 2000
Weather Research and Forecasting (WRF) Model
Weather Research and Forecast (WRF) Model
Promote closer ties between research and operations
Develop an advanced mesoscale forecast and assimilation system
Research:
Design for 1-10 km horizontal grids
Advanced data assimilation and model physics
Accurate and efficient across a broad range of scales
Well-suited for both research and operations
Community model support
Original Partners:
– NCAR Mesoscale and Microscale Meteorology Division– NOAA National Centers for Environmental Prediction– NOAA Forecast Systems Laboratory– OU Center for the Analysis and Prediction of Storms
Additional Collaborators:
– Air Force Weather Agency– NOAA Geophysical Fluid Dynamics Laboratory– NASA GSFC Atmospheric Sciences Division– NOAA National Severe Storms Laboratory– NRL Marine Meteorology Division– EPA Atmospheric Modeling Division– University Community
WRF Project Collaborators
WRF Project Management
WRF OversightBoard
WRF ScienceBoard
WRF Coordinator
WRF Development Teams (5)
Responsible for overall supervision of the WRF Project:
– Monitors plans and progress of the project – Obtains commitments from the heads of participating agencies– Deals with funding requests and budget issues– Provides progress reports to the USWRP IWG and other funding agencies– Appoints the WRF Coordinator and members of the WRF Science Board
Members represent organizations that have made a major commitment of time and resources to the WRF effort
– Steve Lord, chair NOAA/NCEP– Bob Gall NCAR/MMM– Steve Nelson NSF/ATM– Sandy MacDonald NOAA/FSL & GFDL– Col. Charles French USAF/AFWA
WRF Oversight Board (WOB)
Provides technical guidance to the WRF effort to help ensure that WRF will meet the needs of a broad community in both research and operations
– Identifies functional requirements for desired applications– Provides feedback on technical approaches– Promotes active participation in WRF development efforts
Members represent a broad constituency of the research and operational mesoscale forecast community:– Appointed for three-year terms– Communicate via email, web postings, and annual meetings
WRF Science Board (WSB)
Provides overall coordination of the WRF ProjectProvides overall coordination of the WRF Project
Keeps the WOB informed of progress and seeks advice on issues that cannot be resolved at the working level
Appoints WRF Development Teams leaders Works together with Team Leaders to ensure that:
– Overall design goals are achieved– Milestones are accomplished on schedule– Efforts are coordinated among development teams– Technical issue and progress are discussed with the WSB
WRF Coordinator
Numerics and Software
(J. Klemp)
Data Assimilation (T. Schlatter)
Analysis and Validation
(K. Droegemeier)
Community Involvement
(W. Kuo)
Operational Implementation
(G. DiMego)
Dynamic Model Numerics
(W. Skamarock)
Post Processing (L. Wicker)
NCEP Requirements
(G. DiMego)
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AFWA Requirements
(M. Farrar)
Model Testing and Verification
(C. Davis)
Model Physics (J. Brown)
Web Pages & Workshops (J. Dudhia)
Distribution, Documentation,
and Support (J. Dudhia)
Software Architecture,
Standards, and Implementation (J. Michalakes)
Standard Initialization (J. McGinley)
3-D Var (J. Purser)
4-D Var,Ensemble
Techniques (D. Barker)
WRF Development Teams
Performance-Portable– Performance: scaling and time to solution– Architecture independence– No specification of external packages
Run-Time Configurable– Scenarios, domain sizes, nest configurations– Dynamical-core and physics
Maintainability & Extensibility– Single source code– Modular, hierarchical design, coding standards– Plug compatible physics, dynamical cores
WRF Software Objectives
Model domains are decomposed for parallelism on two-levels
– Patch: section of model domain allocated to a distributed memory node– Tile: section of a patch allocated to a shared-memory processor within a node– Distributed memory parallelism is over patches; shared memory parallelism is over tiles within
patches
Single version of code enabled for efficient execution on:
– Distributed-memory multiprocessors
– Shared-memory multiprocessors– Distributed memory clusters of
SMPs
WRF Multi-Layer Domain Decomposition
Logical domain
1 Patch, divided into multiple tiles
Inter-processor communication
WRF Hierarchical Software Architecture
Top-level “Driver” layer isolates computer architecture concerns– Manages execution over multiple nested domains– Provides top level control over parallelism, including patch-decomposition, inter-
processor communication, shared-memory parallelism, etc.– Controls Input/Output
Low-Level “Model” layer code performs actual model computations– Is written to be callable for calculations within a single tile– Allows scientists to work with clean application code
Intermediate “Mediation” layer mediates between model and driver layers
Fortran90 facilitates hierarchical architecture – Allows dynamic memory allocation, derived data-types, pointers– Streamlines grid management
Parallel Scaling on Compaq Computer
Compaq ES40, 41x81x81
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processors
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4 (1d)
ideal
Penalty for IJK Loop Order
IJK versus KIJ for all patch dimensions X,Y=(21,41,81); 41 levels throughout Penalty for IJK decreases with increased length of minor dimension, X Penalty is most severe for sizes typical of a DM patch IJK is strongly favored by vector for adequate length of X Surprise: vector prefers KIJ for short X; but an unlikely result once full physics
2141
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X tile dimension
Y tile dimension
Alpha workstation (EV56)
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Y tiledimension
VPP 5000
Numerical Modeling Issues:
– Equations / variables – Vertical coordinate– Terrain representation– Grid staggering– Time Integration scheme– Advection scheme
Strategy:
– Identify and analyze alternative procedures– Evaluate alternates in idealized simulations– Evaluate in NWP applications as model complexity increases
Numerics for Dynamical Model Solver
Mountain Wave with Step Terrain Coordinate
Split-Explicit Eulerian Model:
– Pressure and temperature diagnosed from thermodynamics– Two time level split-explicit time integration– Flux-form prognostic equations in terms of conserved variables – Accurate shape preserving advection– Both terrain-following height and mass coordinates being tested
Semi-Implicit Semi-Lagrangian Model:
– Unstaggered (A) grid– Forward trajectories with cascade interpolation back to grid– High order compact differencing– Terrain following hybrid coordinate
Prototype Nonhydrostatic Model Solvers
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Conservative variables:
Inviscid, 2-Dequations inCartesiancoordinates
Pressure termsdirectly related to
Flux-Form Equations in Height Coordinates
Flux-Form Equations in Mass Coordinates
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Inviscid, 2-Dequations without rotation:
,,, wWuUConservative variables:
Comparison of Height and Mass Coordinates
Implement and test basic physics in WRF:– Kessler-type (no-ice) microphysics – Lin et al. (graupel included) microphysics – Kain-Fritsch cumulus parameterization – Shortwave radiation (cloud-interactive) from MM5 – Longwave radiation (RRTM) – MRF (Hong and Pan) PBL – Blackadar surface slab ground temperature prediction
Implement a complete suite of research physics packages
Encourage and facilitate community involvement in advanced model physics development and evaluation
Strategy for WRF Model Physics
Essential features of initial 3D-Var system:
– Basic quality control
– Assimilation of conventional observations (surface, radiosonde, aircraft)
– Multivariate analysis
– Adherence to WRF coding standards
Additional features to be added:
– Anisotropic background errors
– Additional observation operators (radar, satellite, wind profiler, etc.)
– Flexible choice of first guess
– Further enhancements
WRF 3D-Var Data-Assimilation System
WRF Model Testing and Verification Strategy
Analytic and converged numerical solutions
– Inviscid dynamics (baroclinic instability, frontogenesis)– Buoyancy driven flow (gravity currents, warm thermals)– Topographic flow (nonhydrostatic, hydrostatic, inertial-gravity mountain waves)– Moist convection (idealized convection with constant eddy mixing)
Regime dependence of nonlinear flows
– Topographic flow (finite amplitude waves, wave overturning, lee vortices)– Moist convection (convective behavior as a function of CAPE and shear)
Observational case studies
– Extratropical cyclones (STORM-FEST case)– Topographic flow (downslope windstorm, orographic precip., cold-air damming)– Moist convection (supercell case, squall-line case, multi-parameter radar case)– PBL-surface physics (1-D dirunal cycle, sea-breeze case, marine inversion and CTD)
Development Task 2000 2001 2002 2003 2004
Basic WRF model (limited physics, standard initialization)
Research quality NWP version of WRF
Model physicsSimple Research suite Advanced
3D-Var assimilation systemBasic Advanced
4D-Var assimilation systemBasic Advanced
Testing for operational use at AFWA
WRF model adapted to NCEP computing environment
Release and support to community Operational deployment
Tentative Timeline for WRF Project
12 January
14 February
29-30 March
23 June
First WRF Oversight Board Meeting
WRF Planning Meeting
WRF Planning Workshop
First Annual WRF Users Workshop
WRF Calendar for 2000
WRF Status & Updates: www.wrf-model.org