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BHP1-1613 Remove Probability of Ignition from Lightning Strike #71

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rjsheperd merged 1 commit into from
Aug 25, 2026
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BHP1-1613 Remove Probability of Ignition from Lightning Strike #71

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275 changes: 141 additions & 134 deletions src/behave/ignite.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -98,130 +98,133 @@ double Ignite::calculateFuelTemperature()
return fuelTemperature_;
}

double Ignite::calculateLightningIgnitionProbability(FractionUnits::FractionUnitsEnum desiredUnits)
{
/*
* The following assumptions are made by Latham:
* - 20% of negative flashes have continuing current
* - 90% of positive flashes have continuing current
* - Latham and Schlieter found a relative frequency of
* 0.723 negative and 0.277 positive strikes
* - Unknown strikes are therefore p = 0.1446 neg + 0.2493 pos
*/

// Probability of continuing current by charge type (Latham)
static const double ccNeg = 0.2;
static const double ccPos = 0.9;

// Relative frequency by charge type (Latham and Schlieter)
static const double freqNeg = 0.723;
static const double freqPos = 0.277;

// Convert duff depth to cm and restrict to maximum of 10 cm.
double duffDepth = igniteInputs_.getDuffDepth(LengthUnits::Centimeters);

duffDepth *= 2.54;
if (duffDepth > 10.0)
{
duffDepth = 10.0;
}

// use hundred hour moisture as duff moisture and conver to percent and restrict to maximum of 40%.
double fuelMoisture = igniteInputs_.getMoistureHundredHour(FractionUnits::Percent);
if (fuelMoisture > 40.0)
{
fuelMoisture = 40.0;
}

double pPos = 0.0;
double pNeg = 0.0;
double probabilityOfLightningIgnition = 0.0;

IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelType = igniteInputs_.getIgnitionFuelBedType();
switch (fuelType)
{
case IgnitionFuelBedType::PonderosaPineLitter:
{
pPos = 0.92 * exp(-0.087 * fuelMoisture);
pNeg = 1.04 * exp(-0.054 * fuelMoisture);
break;
}
case IgnitionFuelBedType::PunkyWoodRottenChunky:
{
pPos = 0.44 * exp(-0.110 * fuelMoisture);
pNeg = 0.59 * exp(-0.094 * fuelMoisture);
break;
}
case IgnitionFuelBedType::PunkyWoodPowderDeep:
{
pPos = 0.86 * exp(-0.060 * fuelMoisture);
pNeg = 0.90 * exp(-0.056 * fuelMoisture);
break;
}
case IgnitionFuelBedType::PunkWoodPowderShallow:
{
pPos = 0.60 - (0.011 * fuelMoisture);
pNeg = 0.73 - (0.011 * fuelMoisture);
break;
}
case IgnitionFuelBedType::LodgepolePineDuff:
{
pPos = 1.0 / (1.0 + exp(5.13 - 0.68 * duffDepth));
pNeg = 1.0 / (1.0 + exp(3.84 - 0.60 * duffDepth));
break;
}
case IgnitionFuelBedType::DouglasFirDuff:
{
pPos = 1.0 / (1.0 + exp(6.69 - 1.39 * duffDepth));
pNeg = 1.0 / (1.0 + exp(5.48 - 1.28 * duffDepth));
break;
}
case IgnitionFuelBedType::HighAltitudeMixed:
{
pPos = 0.62 * exp(-0.050 * fuelMoisture);
pNeg = 0.80 - (0.014 * fuelMoisture);
break;
}
case IgnitionFuelBedType::PeatMoss:
{
pPos = 0.71 * exp(-0.070 * fuelMoisture);
pNeg = 0.84 * exp(-0.060 * fuelMoisture);
break;
}
}

LightningCharge::LightningChargeEnum charge = igniteInputs_.getLightningChargeType();
switch (charge)
{
case LightningCharge::Negative:
{
probabilityOfLightningIgnition = ccNeg * pNeg;
break;
}
case LightningCharge::Positive:
{
probabilityOfLightningIgnition = ccPos * pPos;
break;
}
case LightningCharge::Unknown:
{
probabilityOfLightningIgnition = freqPos * ccPos * pPos + freqNeg * ccNeg * pNeg;
break;
}
}

// Constrain result
if (probabilityOfLightningIgnition < 0.0)
{
probabilityOfLightningIgnition = 0.0;
}
if (probabilityOfLightningIgnition > 1.0)
{
probabilityOfLightningIgnition = 1.0;
}

return FractionUnits::fromBaseUnits(probabilityOfLightningIgnition, desiredUnits);
}
/* Deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// double Ignite::calculateLightningIgnitionProbability(FractionUnits::FractionUnitsEnum desiredUnits)
// {
// /*
// * The following assumptions are made by Latham:
// * - 20% of negative flashes have continuing current
// * - 90% of positive flashes have continuing current
// * - Latham and Schlieter found a relative frequency of
// * 0.723 negative and 0.277 positive strikes
// * - Unknown strikes are therefore p = 0.1446 neg + 0.2493 pos
// */
//
// // Probability of continuing current by charge type (Latham)
// static const double ccNeg = 0.2;
// static const double ccPos = 0.9;
//
// // Relative frequency by charge type (Latham and Schlieter)
// static const double freqNeg = 0.723;
// static const double freqPos = 0.277;
//
// // Convert duff depth to cm and restrict to maximum of 10 cm.
// double duffDepth = igniteInputs_.getDuffDepth(LengthUnits::Centimeters);
//
// duffDepth *= 2.54;
// if (duffDepth > 10.0)
// {
// duffDepth = 10.0;
// }
//
// // use hundred hour moisture as duff moisture and conver to percent and restrict to maximum of 40%.
// double fuelMoisture = igniteInputs_.getMoistureHundredHour(FractionUnits::Percent);
// if (fuelMoisture > 40.0)
// {
// fuelMoisture = 40.0;
// }
//
// double pPos = 0.0;
// double pNeg = 0.0;
// double probabilityOfLightningIgnition = 0.0;
//
// IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelType = igniteInputs_.getIgnitionFuelBedType();
// switch (fuelType)
// {
// case IgnitionFuelBedType::PonderosaPineLitter:
// {
// pPos = 0.92 * exp(-0.087 * fuelMoisture);
// pNeg = 1.04 * exp(-0.054 * fuelMoisture);
// break;
// }
// case IgnitionFuelBedType::PunkyWoodRottenChunky:
// {
// pPos = 0.44 * exp(-0.110 * fuelMoisture);
// pNeg = 0.59 * exp(-0.094 * fuelMoisture);
// break;
// }
// case IgnitionFuelBedType::PunkyWoodPowderDeep:
// {
// pPos = 0.86 * exp(-0.060 * fuelMoisture);
// pNeg = 0.90 * exp(-0.056 * fuelMoisture);
// break;
// }
// case IgnitionFuelBedType::PunkWoodPowderShallow:
// {
// pPos = 0.60 - (0.011 * fuelMoisture);
// pNeg = 0.73 - (0.011 * fuelMoisture);
// break;
// }
// case IgnitionFuelBedType::LodgepolePineDuff:
// {
// pPos = 1.0 / (1.0 + exp(5.13 - 0.68 * duffDepth));
// pNeg = 1.0 / (1.0 + exp(3.84 - 0.60 * duffDepth));
// break;
// }
// case IgnitionFuelBedType::DouglasFirDuff:
// {
// pPos = 1.0 / (1.0 + exp(6.69 - 1.39 * duffDepth));
// pNeg = 1.0 / (1.0 + exp(5.48 - 1.28 * duffDepth));
// break;
// }
// case IgnitionFuelBedType::HighAltitudeMixed:
// {
// pPos = 0.62 * exp(-0.050 * fuelMoisture);
// pNeg = 0.80 - (0.014 * fuelMoisture);
// break;
// }
// case IgnitionFuelBedType::PeatMoss:
// {
// pPos = 0.71 * exp(-0.070 * fuelMoisture);
// pNeg = 0.84 * exp(-0.060 * fuelMoisture);
// break;
// }
// }
//
// LightningCharge::LightningChargeEnum charge = igniteInputs_.getLightningChargeType();
// switch (charge)
// {
// case LightningCharge::Negative:
// {
// probabilityOfLightningIgnition = ccNeg * pNeg;
// break;
// }
// case LightningCharge::Positive:
// {
// probabilityOfLightningIgnition = ccPos * pPos;
// break;
// }
// case LightningCharge::Unknown:
// {
// probabilityOfLightningIgnition = freqPos * ccPos * pPos + freqNeg * ccNeg * pNeg;
// break;
// }
// }
//
// // Constrain result
// if (probabilityOfLightningIgnition < 0.0)
// {
// probabilityOfLightningIgnition = 0.0;
// }
// if (probabilityOfLightningIgnition > 1.0)
// {
// probabilityOfLightningIgnition = 1.0;
// }
//
// return FractionUnits::fromBaseUnits(probabilityOfLightningIgnition, desiredUnits);
// }

void Ignite::setAirTemperature(double airTemperature, TemperatureUnits::TemperatureUnitsEnum temperatureUnites)
{
Expand Down Expand Up @@ -253,18 +256,19 @@ void Ignite::setDuffDepth(double duffDepth, LengthUnits::LengthUnitsEnum lengthU
igniteInputs_.setDuffDepth(duffDepth, lengthUnits);
}

void Ignite::setLightningChargeType(LightningCharge::LightningChargeEnum lightningChargeType)
{
igniteInputs_.setLightningChargeType(lightningChargeType);
}
/* Deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// void Ignite::setLightningChargeType(LightningCharge::LightningChargeEnum lightningChargeType)
// {
// igniteInputs_.setLightningChargeType(lightningChargeType);
// }

void Ignite::updateIgniteInputs(double moistureOneHour, double moistureHundredHour, FractionUnits::FractionUnitsEnum moistureUnits,
double airTemperature, TemperatureUnits::TemperatureUnitsEnum temperatureUnits, double sunShade, FractionUnits::FractionUnitsEnum sunShadeUnits,
IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelBedType, double duffDepth, LengthUnits::LengthUnitsEnum duffDepthUnits,
LightningCharge::LightningChargeEnum lightningChargeType)
IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelBedType, double duffDepth, LengthUnits::LengthUnitsEnum duffDepthUnits)
{
igniteInputs_.updateIgniteInputs(moistureOneHour, moistureHundredHour, moistureUnits, airTemperature,
temperatureUnits, sunShade, sunShadeUnits, fuelBedType, duffDepth, duffDepthUnits, lightningChargeType);
temperatureUnits, sunShade, sunShadeUnits, fuelBedType, duffDepth, duffDepthUnits);
}

double Ignite::getAirTemperature(TemperatureUnits::TemperatureUnitsEnum desiredUnits)
Expand Down Expand Up @@ -302,10 +306,13 @@ double Ignite::getDuffDepth(LengthUnits::LengthUnitsEnum desiredUnits)
return igniteInputs_.getDuffDepth(desiredUnits);
}

LightningCharge::LightningChargeEnum Ignite::getLightningChargeType()
{
return igniteInputs_.getLightningChargeType();
}

/* Deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// LightningCharge::LightningChargeEnum Ignite::getLightningChargeType()
// {
// return igniteInputs_.getLightningChargeType();
// }

bool Ignite::isFuelDepthNeeded()
{
Expand Down
15 changes: 10 additions & 5 deletions src/behave/ignite.h
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Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -43,20 +43,23 @@ class Ignite
void initializeMembers();

double calculateFirebrandIgnitionProbability(FractionUnits::FractionUnitsEnum desiredUnits);
double calculateLightningIgnitionProbability(FractionUnits::FractionUnitsEnum desiredUnits);
/* Code is deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// double calculateLightningIgnitionProbability(FractionUnits::FractionUnitsEnum desiredUnits);

void setMoistureOneHour(double moistureOneHour, FractionUnits::FractionUnitsEnum moistureUnits);
void setMoistureHundredHour(double moistureHundredHour, FractionUnits::FractionUnitsEnum moistureUnits);
void setAirTemperature(double airTemperature, TemperatureUnits::TemperatureUnitsEnum temperatureUnites);
void setSunShade(double sunShade, FractionUnits::FractionUnitsEnum sunShadeUnits);
void setDuffDepth(double duffDepth, LengthUnits::LengthUnitsEnum lengthUnits);
void setIgnitionFuelBedType(IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelBedType_);
void setLightningChargeType(LightningCharge::LightningChargeEnum lightningChargeType);
/* Code is deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// void setLightningChargeType(LightningCharge::LightningChargeEnum lightningChargeType);

void updateIgniteInputs(double moistureOneHour, double moistureHundredHour, FractionUnits::FractionUnitsEnum moistureUnits,
double airTemperature, TemperatureUnits::TemperatureUnitsEnum temperatureUnits, double sunShade, FractionUnits::FractionUnitsEnum sunShadeUnits,
IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelBedType, double duffDepth, LengthUnits::LengthUnitsEnum duffDepthUnits,
LightningCharge::LightningChargeEnum lightningChargeType);
IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelBedType, double duffDepth, LengthUnits::LengthUnitsEnum duffDepthUnits);

double getAirTemperature(TemperatureUnits::TemperatureUnitsEnum desiredUnits);
double getFuelTemperature(TemperatureUnits::TemperatureUnitsEnum desiredUnits);
Expand All @@ -65,7 +68,9 @@ class Ignite
double getSunShade(FractionUnits::FractionUnitsEnum desiredUnits);
double getDuffDepth(LengthUnits::LengthUnitsEnum desiredUnits);
IgnitionFuelBedType::IgnitionFuelBedTypeEnum getFuelBedType();
LightningCharge::LightningChargeEnum getLightningChargeType();
/* Code is deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// LightningCharge::LightningChargeEnum getLightningChargeType();

// isFuelDepthNeeded() can be used in applications to determine whether user input of fuel bed depth is
// neccessary based on the current value of fuel bed used by the ignite module
Expand Down
24 changes: 13 additions & 11 deletions src/behave/igniteInputs.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -31,16 +31,14 @@ void IgniteInputs::initializeMembers()

void IgniteInputs::updateIgniteInputs(double moistureOneHour, double moistureHundredHour, FractionUnits::FractionUnitsEnum moistureUnits,
double airTemperature, TemperatureUnits::TemperatureUnitsEnum temperatureUnits, double sunShade, FractionUnits::FractionUnitsEnum sunShadeUnits,
IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelBedType, double duffDepth, LengthUnits::LengthUnitsEnum duffDepthUnits,
LightningCharge::LightningChargeEnum lightningChargeType)
IgnitionFuelBedType::IgnitionFuelBedTypeEnum fuelBedType, double duffDepth, LengthUnits::LengthUnitsEnum duffDepthUnits)
{
setMoistureOneHour(moistureOneHour, moistureUnits);
setMoistureHundredHour(moistureHundredHour, moistureUnits);
setAirTemperature(airTemperature, temperatureUnits);
setSunShade(sunShade, sunShadeUnits);
fuelBedType_ = fuelBedType;
setDuffDepth(duffDepth, duffDepthUnits);
lightningChargeType_ = lightningChargeType;
}

void IgniteInputs::setMoistureOneHour(double moistureOneHour, FractionUnits::FractionUnitsEnum moistureUnits)
Expand Down Expand Up @@ -73,10 +71,12 @@ void IgniteInputs::setDuffDepth(double duffDepth, LengthUnits::LengthUnitsEnum l
duffDepth_ = LengthUnits::toBaseUnits(duffDepth, lengthUnits);
}

void IgniteInputs::setLightningChargeType(LightningCharge::LightningChargeEnum lightningChargeType)
{
lightningChargeType_ = lightningChargeType;
}
/* Code is deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// void IgniteInputs::setLightningChargeType(LightningCharge::LightningChargeEnum lightningChargeType)
// {
// lightningChargeType_ = lightningChargeType;
//}

double IgniteInputs::getAirTemperature(TemperatureUnits::TemperatureUnitsEnum desiredUnits)
{
Expand Down Expand Up @@ -108,7 +108,9 @@ double IgniteInputs::getDuffDepth(LengthUnits::LengthUnitsEnum desiredUnits)
return LengthUnits::fromBaseUnits(duffDepth_,desiredUnits);
}

LightningCharge::LightningChargeEnum IgniteInputs::getLightningChargeType()
{
return lightningChargeType_;
}
/* Code is deprecated as the science is no longer considered reliable.
There is no known method to accurately calculate Probability of Ignition from a lightning strike. */
// LightningCharge::LightningChargeEnum IgniteInputs::getLightningChargeType()
// {
// return lightningChargeType_;
// }
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