Environmental Modeling

1

• Environmental Modeling
• Integration of GIS with Env Models

2
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.

3
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

4
2. Tasks

• Create 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

5
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

6
4. Data

• Surface
• wind speed
• wind direction
• temperature (21 sites)
• 124,000 DEM
• Upper air
• 1 vertical profile of wind and temperature

7
5. GIS Processes

• Re-sample DEM to 150m resolution
• Attach locations to elevation and weather data
  for KRISSY

8
6. Model I Again

• Model constraints
• - Concordance with surface and
• upper air observations
• - Laws of physics

9
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

10
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

11
7. Model II..

451350(e) vs. 22503150(w) -450450(n)
vs.13502250(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-wn-s, or use sin or cos.
Sin180 0 Cos180 -1
12
7. GIS Process II

• Display fire potential using a set of graduated
  point symbols

13
8. Possible Error Sources

• Resampling terrain data
• Surface wind observation
• Spatial distribution of the wind observation