28 research outputs found
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Numerical Simulations of Two Wildfire Events Using a Combined Modeling System (HIGRAD/BEHAVE)
The ability to accurately forecast the spread of a wildfire would significantly reduce human suffering and loss of life, the destruction of property, and expenditures for assessment and recovery. To help achieve this goal we have developed a model which accurately simulates the interactions between winds and the heat source associated with a wildfire. We have termed our new model HIGRAD or High resolution model for strong GRA-Dient applications. HIGRAD employs a sophisticated numerical technique to prevent numerical Oscillations from occurring in the vicinity of the lire. Of importance for fire modeling, HIGRAD uses a numerical technique which allows for the use of a compressible equation set, but without the time-step restrictions associated with the propagation of sound-waves
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A coupled regional climate-biosphere model for climate studies
This is the final report of a three-year, Laboratory-Directed Research and Development (LDRD) project at the Los Alamos National Laboratory (LANL). The objective of this project has been to develop and test a regional climate modeling system that couples a limited-area atmospheric code to a biosphere scheme that properly represents surface processes. The development phase has included investigations of the impact of variations in surface forcing parameters, meteorological input data resolution, and model grid resolution. The testing phase has included a multi-year simulation of the summer climate over the Southwest United States at higher resolution than previous studies. Averaged results from a nine summer month simulation demonstrate the capability of the regional climate model to produce a representative climatology of the Southwest. The results also show the importance of strong summertime thermal forcing of the surface in defining this climatology. These simulations allow us to observe the climate at much higher temporal and spatial resolutions than existing observational networks. The model also allows us to see the full three-dimensional state of the climate and thereby deduce the dominant physical processes at any particular time
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Validation of Coupled Atmosphere-Fire Behavior Models
Recent advances in numerical modeling and computer power have made it feasible to simulate the dynamical interaction and feedback between the heat and turbulence induced by wildfires and the local atmospheric wind and temperature fields. At Los Alamos National Laboratory, the authors have developed a modeling system that includes this interaction by coupling a high resolution atmospheric dynamics model, HIGRAD, with a fire behavior model, BEHAVE, to predict the spread of wildfires. The HIGRAD/BEHAVE model is run at very high resolution to properly resolve the fire/atmosphere interaction. At present, these coupled wildfire model simulations are computationally intensive. The additional complexity of these models require sophisticated methods for assuring their reliability in real world applications. With this in mind, a substantial part of the research effort is directed at model validation. Several instrumented prescribed fires have been conducted with multi-agency support and participation from chaparral, marsh, and scrub environments in coastal areas of Florida and inland California. In this paper, the authors first describe the data required to initialize the components of the wildfire modeling system. Then they present results from one of the Florida fires, and discuss a strategy for further testing and improvement of coupled weather/wildfire models
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Case study: Wildfire visualization
The ability to forecast the progress of crisis events would significantly reduce human suffering and loss of life, the destruction of property, and expenditures for assessment and recovery. Los Alamos National Laboratory has established a scientific thrust in crisis forecasting to address this national challenge. In the initial phase of this project, scientists at Los Alamos are developing computer models to predict the spread of a wildfire. Visualization of the results of the wildfire simulation will be used by scientists to assess the quality of the simulation and eventually by fire personnel as a visual forecast of the wildfire`s evolution. The fire personnel and scientists want the visualization to look as realistic as possible without compromising scientific accuracy. This paper describes how the visualization was created, analyzes the tools and approach that was used, and suggests directions for future work and research
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Regional climatology sensitivity studies
Recent interest in understanding climate and climate change at regional-scales has led to the application of mesoscale models for regional climatology studies. These models can provide an understanding of climate processes in a physically consistent way at much higher resolution than presently offered by GCMs. In recent work, we have tried to address questions in the RAMS mesoscale model to establish confidence in our modeling procedure. A more rigorous comparison of our modeling results with various data sets is reported in Roads et al. (1992). In the present paper, we use two simple numerical experiments to examine the impact of grid configuration on the predicted precipitation field from the RAMS model. We intend to demonstrate that the choice of the lateral boundaries and grid configurations can significantly impact the predicted fields of interest
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Regional-scale simulations of the western US climate
Over the past two decades the meteorological community has witnessed the evolution of general circulation models (GCMs) from studies attempting to simulate realistic large-scale dynamical regimes and energy transports to present investigations examining future climate change scenarios. From these pioneering studies, we were inspired to begin to develop regional climatologies with the Colorado State University Regional Atmospheric Modeling System (CSU-RAMS). Our major goal is to develop a better understanding of the hydrologic cycle in the mountainous, and west. An advantage of using the RAMS code is that we can generate detailed descriptions of precipitation processes, which will hopefully translate into realistic surface yields of both rain and snow. In the ensuing sections, we first describe the model and its microphysics parameterizations, then continue with our methodology for incorporating large-scale data into the model grid. Preliminary results demonstrating the mesoscale variation of precipitation over the mountainous western US are then presented
Modeling Spatial and Temporal Dynamics of Wind Flow and Potential Fire Behavior Following a Mountain Pine Beetle Outbreak in a Lodgepole Pine Forest
Patches of live, dead, and dying trees resulting from bark beetle-caused mortality alter spatial and temporal variability in the canopy and surface fuel complex through changes in the foliar moisture content of attacked trees and through the redistribution of canopy fuels. The resulting heterogeneous fuels complexes alter within-canopy wind flow, wind fluctuations, and rate of fire spread. However, there is currently little information about the potential influence of different rates and patterns of mortality on wind flow and fire behavior following bark beetle outbreaks. In this study, we contrasted within-canopy wind flow and fire rate-of-spread (ROS) at two different ambient wind speeds using FIRETEC for two differing bark beetle attack trajectories for a lodgepole pine (Pinus contorta) forest. These two attack trajectories represent different realizations of a bark beetle outbreak and result in different amounts and patterns of mortality through time. Our simulations suggested that the mean within-canopy wind velocities increased through time following the progression of mortality. In addition, we found that for a given level of mortality, a bark beetle outbreak that resulted in a higher degree of aggregation of canopy fuels had greater mean within-canopy wind velocities due to the channeling of wind flow. These findings suggest that bark beetle mortality can influence the mean within-canopy wind flow in two ways: first, by reducing the amount of vegetation present in the canopy acting as a source of drag; and second, by altering spatial patterns of vegetation that can lead to channeling of wind flow. Changes in the fire rate-of-spread were positively related to the level and continuity of bark beetle mortality. Peak rates of spread were between 1.2 and 2.7 times greater than the pre-outbreak scenario and coincided with a high level of mortality and minimal loss of canopy fuels. Following the loss of canopy fuels the rate of fire spread declined to levels below the initial phases of the outbreak in low wind speed cases but remained above pre-outbreak levels in high wind speed cases. These findings suggest that the rate and pattern of mortality arising from a bark beetle outbreak exerts significant influence on the magnitude and timing of alterations to the within-canopy wind flow and rate of fire spread. Our findings help clarify existing knowledge gaps related to the effect of bark beetle outbreaks on fire behavior and could explain potential differences in the reported effects of bark beetle outbreaks on fire behavior through time