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  • Wildfires

    Chun-Lung Lim and Charles Erwin

  • THE WEATHERTHE WEATHER RESEARCH ANDRESEARCH AND

    FORECAST MODELFORECAST MODEL (WRF)(WRF)

  • What makes WRF next-generationWhat makes WRF next-generation mesoscalemesoscale forecast model ? forecast model ?

    Advance the understanding and the prediction of mesoscale precipitation systems and to promote closer ties between the research and operational forecasting communities. Efficiency, portability, maintainability, and extensibility.

  • SOFTWARESOFTWARE ARCHITECTUREARCHITECTURE

  • Runge-Kutta MethodRunge-Kutta Method

  • Driver LayerDriver Layer

    Handles run-time allocation and parallel decomposition of model domain data structures. Organization, management, interaction, and control over nested domains, including the main time loop in the model. High level interfaces to I/O operations on model domains. It is interface to other components when WRF is part of a larger coupled system of applications.

  • Mediation LayerMediation Layer

    Encompasses one time-step of a particular dynamical core on a single model domain. The current WRF implementation uses the Message Passing Interface (MPI) communication package. Shared-memory parallelism over tiles in the solve routines is using OpenMP.

  • ICCICC’’s High Performance Computings High Performance Computing

  • Model LayerModel Layer

    Comprises the actual computational routines that make up the model: advection, diffusion, physical parameterizations, and so forth. The subroutines are called through a standard Model Layer Interface. The interface ensures that a Model Layer package incorporated into WRF will work on any parallel computer. Model layer routines have data dependencies rely on the mediation layer to perform the necessary interprocessor communication.

  • The RegistryThe Registry

    It is a concise database of information about WRF data structures and a mechanism for automatically generating large sections of WRF code. The Registry data base is a collection of tables that lists and describes the WRF state variables and arrays with their attributes such as dimensionality and so fourth. Registry generates code for interfaces between layers of the infrastructure, packing and unpacking code for communication and nesting, and field-by-field calls to routines for model I/O.

  • Moving NestsMoving Nests

  • PERFORMANCEPERFORMANCE

  • Implementation of Implementation of WildlandWildland Fire Model Component inFire Model Component in

    the WRF modelthe WRF model

  • Functionalities of the Functionalities of the WildlandWildland Fire Model Fire Model ComponentComponent

    Extension of the Clark-Hall atmospheric model. Atmosphere-wildland fire simulation model has been developed to represent a complex interactions between fires and local winds. Helps to track atmospheric wind velocities and calculate fire spread more precisely. Handles large releases of buoyancy and accurately represent fine- scale motions in complex terrain. Ingest large-scale gridded data to incorporate a changing mesoscale atmospheric environment. Telescope down to the meter-sized fine dynamic scales of vortices in the fire line through horizontal and vertical grid refinement.

  • BenefitsBenefits

    The availability of a coupled atmosphere-fire model in a well- supported community model for eventual community research. Can build a stable framework in other scientific components related to the Wildland Fire Research and Development Collaboratory. Provide eventual operational capability with operational applications like smoke management … A test of WRF with strong forcing at small scales. Reduction in the redundancy of effort developing needed capabilities within the Clark-Hall model .

  • Numerical modelNumerical model

    • Background - 3-D nonhydrostatic atmospheric prediction model coupled with

    an empirical fire spread model with sensible and latent heat flux from the fire feed back to the atmosphere to produce fire winds.

    - The atmospheric winds drive the fire propagation.

    • Wildfire simulation model represents the complex interactions between a fire and local wind.

  • BURNUP algorithmBURNUP algorithm

    Characterizes how the fire consumes fuels of different sizes over time.

    Equation : 1-F = exp(-t/W)

  • Implementation of Fire Module in WRFImplementation of Fire Module in WRF

    Fire module will be implemented as an added physics option in WRF. Fire-atmosphere coupling will occur through passing winds from the lowest WRF level to the fire module. The fire module will use those winds to predict the fire spread and subsequent heat and water vapor emissions. Heat and water vapor emissions from the fire will be passed back to WRF and distributed vertically through an assumed extinction depth.

  • Initialization of Fire EnvironmentInitialization of Fire Environment

    Three environmental factors that influence fire behavior are :

    1. Topography 2. Weather 3. Fuel

  • TopographyTopography

    Fires spread much faster in upslope than flat ground. Fine-scale topography features as a factor in local airflows plays a role in fire behavior.

  • WeatherWeather

    Weather impacting the fire. The weather impacts on the fire can be obtained by the winds model in WRF. Winds model could be used to simulate changes in dead fuel moisture which responds with time lags corresponding to the size of the fuel particles.

    - A second feedback loop between the fire and the environment.

  • FuelFuel

    Not all vegetation is burnable. Live vegetation may be dried and ignited by fire (live fuel). Forest floor needles, cured grasses and branches (dead fuel) play more important role in fire behavior.

  • Links with other modulesLinks with other modules

     WRF-Chem is an atmospheric chemistry package linked to WRF for simulation of atmospheric chemistry and aerosols.

     The combined application of WRF-Chem and WRF-Fire will allow the user to create a simulation of Wildland fire.

  • Numerical Simulation of WildfiresNumerical Simulation of Wildfires

  • ReferencesReferences

    URLs

     http://mathworld.wolfram.com/Runge-KuttaMethod.html  http://www.wrf-model.org/index.php  http://www.llnl.gov/computing/hpc/training/#training_materials  http://box.mmm.ucar.edu/research/wildfire/wrf/wrf_summary.html  http://box.mmm.ucar.edu/research/wildfire/wrf/wrf_fire.html

    Research Papers

    The Weather Research and Forecast Model: Software Architecture and Performance by J Michalakes, J.Dudhia, D.Gill, T.Henderson, J.Klemp, W.Skamarock, W.Wang

    Implementation of Wildland Fire Model Component in the Weather Research and Forecasting (WRF) model by Janice Coen (MMM/RAP) and Ned Patton (MMM)

    WRF-Fire: A Coupled Atmosphere-Fire Module for WRF by Ediward G.Patton and Janice L.Coen. National Center for Atmospheric Research, Boulder, CO

  • Wildfire Simulation SoftwareWildfire Simulation Software

    Charles ErwinCharles Erwin

  • CS 521: Computational Science 2

    Simple Wildfire Simulator from NOVASimple Wildfire Simulator from NOVA

     http://www.pbs.org/wgbh/nova/fire/simulation.html (requires Flash)

     Wildfire Simulator is a simple computer simulation that predicts the behavior of fire in a wildland environment.

     Not meant for research, only to demonstrate some basic ideas about wildfire simulation.

     Programming for this feature is derived from FARSITE.

  • CS 521: Computational Science 3

    EMBYR: EMBYR: ““Ecological Model for BurningEcological Model for Burning the Yellowstone Regionthe Yellowstone Region””

     Created by William W. Hargrove and Robert H. Gardner  Designed to simulate wildfires, the subsequent pattern of

    vegetation, and then the next generation of burn patterns.

     While the EMBYR model parameters could be adjusted to reproduce a particular historical wildfire exactly, it is more important to reproduce any wildfire relatively well on average.

     EMBYR can generate "Risk Maps", which are constructed from many replications of a single simulated fire. Cells which burned in many of the replications are colored black, while cells which burned in only a few simulations are colored white, with gray levels in intermediate cases.

  • CS 521: Computational Science 4

    EMBYR Fire ModelEMBYR Fire Model

     The fire model, EMBYR, depicts the landscape as a grid in which the dimension of each cell is 50 m (2500 m2).

     Diffusive Spread: Fire spreads from each ignited cell to any of eight unburned neighbors (the four adjacent cells and four diagonal cells) as an independent stochastic event with probability I, where I may range from 0 to 1.

     Each cell burns for a single time step of variable length, and the fire goes out if new sites are not ignited at each time step.

     Theoretical studies have demonstrated that if I is less then a critical value, fires are unlikely to propagate across the landscape c

    i

  • CS 521: Computational Science 5

    EMBYR Fire Model (cont)EMBYR Fire Model (cont)

     They estimated by performing 50 simulations for each value of I (