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Discover how GIS data and meteorological models can predict fire potential in San Jacinto Mountain, Southern California, by integrating topographic and weather databases. Implement diagnostic wind and slope-wind interaction fire models for accurate predictions.
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Environmental Modeling Integration of GIS with Env Models
1. Issue • Predict fire potential in San Jacinto Mountain, Southern California • using GIS data and meteorological data and • meteorological models Zack, J.A. and R.A. Minnich, 1991. Integration of geographic information systems with a diagnostic wind field model for fire management. Forest Science, 37(2): 560-573.
1. Causal factors of wildfire • Hot and dry weather - high temperature and low humidity • Windy - high wind speed and certain wind direction • Fuels - dry grasses and shrubs
2. Tasks • Find topographic and weather databases • Use GIS and weather data as input for a diagnostic wind model to estimate surface wind field • Combine output of the wind model and slope as input for a slope-wind interaction fire model to estimate fire potential • Use GIS to display model results
3. Model I A diagnostic wind field model: KRISSY Input (1) 3D topography, (2) vertical profile of horizontal wind speed and direction, (3) synoptic-scale pressure gradient, and (4) inverse distance squared interpolation To estimate wind direction and speed for surface grids and above surface grids
4. Data • Surface: wind speed wind direction temperature (21 sites) 1:24,000 DEM • Upper air: 1 vertical profile of wind and temperature
5. GIS Processes • Re-sample DEM to 150m resolution • Attach locations to elevation and weather data for KRISSY
6. Model I Again Model constraints: - Concordance with surface and upper air observations - Laws of physics
6. Model I .. • Output • Convert model output in GIS: elevation, wind direction, wind speed, E-W, N-S, and vertical component of wind • Prepare slope angle and aspect for the second model
7. Model II • Slope-Wind Interaction Fire Model (SWIF) • Fire spread rates increase up-slopes and change with slope aspect • SWIFi,j = Vi,j {1+[(sin Si,j)0.5* (cos (i,j-i,j))]} Vi,j -wind speed (estimated by KRISSY) Si,j -slope angle (degree) i,j - wind direction (estimated by KRISSY) i,j -slope aspect
7. Model II.. 45~1350(e) vs. 2250~3150(w) -450~450(n) vs.1350~2250(s) Sin0 = 0 Cos0 = 1 Sin270 = -1 Cos270 = 0 Sin90 = 1 Cos90 = 0 3. 4. Aspect is a circular variable. To differentiate its circular values, divide it into e-w|n-s, or use sin or cos. Sin180 = 0 Cos180 = -1
7. GIS Process II • Display fire potential using a set of graduated point symbols
8. Possible Error Sources • Resampling terrain data • Surface wind observation • Spatial distribution of the wind observation