Crowning Initiation Foliar Moisture Threshold Checker
Evaluate named Van Wagner crown-initiation critical-intensity equation using canopy base height and dry-basis foliar moisture; exceeding this model threshold is not proof of active crown fire or an operational safety assessment.
Description
Van Wagner's crown-initiation model links canopy base height and foliar moisture to a critical surface fireline intensity.
Van Wagner's crown-initiation model links canopy base height and foliar moisture to a critical surface fireline intensity. Initiation conditions differ from sustained active crown-fire spread.1, 2
Evaluate named Van Wagner crown-initiation critical-intensity equation using canopy base height and dry-basis foliar moisture; exceeding this model threshold is not proof of active crown fire or an operational safety assessment.
When to use Crowning Initiation Foliar Moisture Threshold Checker
Use this tool to evaluate named Van Wagner crown-initiation critical-intensity equation using canopy base height and dry-basis foliar moisture; exceeding this model threshold is not proof of active crown fire or an operational safety assessment.
Gather the tree inventory, plot measurements or model parameters. Check diameter, area, time and moisture conventions; keep paired observations aligned.
How to use Crowning Initiation Foliar Moisture Threshold Checker and understand its results
- Gather the tree inventory, plot measurements or model parameters. Check diameter, area, time and moisture conventions; keep paired observations aligned.
- Enter canopyBaseHeightM, foliarMoisturePercentDryBasis, observedSurfaceIntensityKwPerM using the field table and calculation rules, then run the tool.
- Read vanWagnerCriticalIntensityKwPerM, observedToCriticalIntensityRatio, aboveModelInitiationThreshold. The explanation below defines the units, signs, ordering and any flags or placeholder values.
- If the tool reports an input issue, correct the values and run it again. Apply the stated assumptions when interpreting a successfully returned result.
| Input field | Meaning | Value type; see rules below | Requirement |
|---|---|---|---|
| canopyBaseHeightM | Canopy base height m | number | Required |
| foliarMoisturePercentDryBasis | Foliar moisture percent dry basis | number | Required |
| observedSurfaceIntensityKwPerM | Observed surface intensity kw per m | number | Required |
Use positive canopy base height and nonnegative dry-basis foliar moisture percent and observed intensity. Return critical intensity, observed/critical ratio and a flag when observed intensity is at least critical, including equality despite the output's above-threshold wording.
critical kW/m=[0.01 × canopy base m × (460+25.9 × dry-basis foliar moisture %)]^1.5 Units, indexing, boundary conditions and exceptional cases are defined in the calculation rules above.
| Output field | Meaning | Value type |
|---|---|---|
| vanWagnerCriticalIntensityKwPerM | Van wagner critical intensity kw per m | number |
| observedToCriticalIntensityRatio | Observed to critical intensity ratio | number |
| aboveModelInitiationThreshold | Above model initiation threshold | boolean |
{
"input": {
"canopyBaseHeightM": 2,
"foliarMoisturePercentDryBasis": 100,
"observedSurfaceIntensityKwPerM": 100
},
"output": {
"vanWagnerCriticalIntensityKwPerM": 476.42523023030594,
"observedToCriticalIntensityRatio": 0.20989652448015733,
"aboveModelInitiationThreshold": false
}
}Limitations and assumptions
The named empirical threshold does not prove active crown fire or provide operational safety assessment.
Numeric inputs and returned numeric values must be finite; an unrepresentable returned value produces an error. Missing required fields, extra fields, wrong value types and violations of the calculation rules are input errors. A successfully returned false flag is an evaluated outcome; its meaning is explained above.
Alternative or Complementary methods
Use Byram Fireline Intensity kW/m: Compute Byram heat-yield×consumed-fuel×front-spread fireline intensity using supplied dry fuel consumption, not full fuel load or a fire-danger/response recommendation. For a complementary task, use Flame Length From Fireline Intensity: Apply supplied unit-specific fireline-intensity/flame-length calibration inside its domain; no universal coefficient or tactics/safe-distance determination.
Further background: Assessing crown fire potential by linking models of surface and crown fire behavior.
References
Similar or alternative tools
- Byram Fireline Intensity kW/m
Compute Byram heat-yield×consumed-fuel×front-spread fireline intensity using supplied dry fuel consumption, not full fuel load or a fire-danger/response recommendation.
- Flame Length From Fireline Intensity
Apply supplied unit-specific fireline-intensity/flame-length calibration inside its domain; no universal coefficient or tactics/safe-distance determination.