improver.fire_weather.initial_spread_index module

improver.fire_weather.initial_spread_index module#

class InitialSpreadIndex[source]#

Bases: FireWeatherBase

Plugin to calculate the Initial Spread Index (ISI).

The ISI is a numerical rating of the expected rate of fire spread. It combines the effects of wind and the Fine Fuel Moisture Code (FFMC) on the rate of spread without the influence of variable quantities of fuel.

This process is adapted directly from:

Equations and FORTRAN Program for the Canadian Forest Fire Weather Index System (C.E. Van Wagner and T.L. Pickett, 1985). Pages 7-8, Equations 24-26.

Expected input units:

  • Wind speed: km/h

  • Fine Fuel Moisture Code (FFMC): dimensionless (0-101)

INPUT_ATTRIBUTE_MAPPINGS: dict[str, str] = {'fine_fuel_moisture_code': 'input_ffmc'}#
INPUT_CUBE_NAMES: list[str] = ['wind_speed', 'fine_fuel_moisture_code']#
METADATA_SOURCE_CUBE: str = 'fine_fuel_moisture_code'#
OUTPUT_CUBE_NAME: str = 'initial_spread_index'#
VALID_OUTPUT_RANGE: tuple[float | None, float | None] | None = (0.0, 100)#
_abc_impl = <_abc._abc_data object>#
_calculate()[source]#

Calculates the Initial Spread Index (ISI) from wind and FFMC.

This uses Steps 1 & 2 from Van Wagner and Pickett (1985), page 8.

Return type:

ndarray

Returns:

The calculated ISI values.

_calculate_fine_fuel_moisture()[source]#

Calculates the moisture content from the FFMC value.

From Van Wagner and Pickett (1985), Page 5: Equation 1.

_calculate_isi(spread_factor, wind_function)[source]#

Calculates the Initial Spread Index (ISI).

From Van Wagner and Pickett (1985), Page 7: Equation 26.

Parameters:

  • spread_factor (ndarray) – The spread factor values.

  • wind_function (ndarray) – The wind function values.

Return type:

ndarray

Returns:

The calculated ISI values.

_calculate_spread_factor()[source]#

Calculates the spread factor component for ISI.

From Van Wagner and Pickett (1985), Page 7: Equation 25.

Return type:

ndarray

Returns:

The spread factor values.

_calculate_wind_function()[source]#

Calculates the wind function component of ISI.

From Van Wagner and Pickett (1985), Page 7: Equation 24.

Return type:

ndarray

Returns:

The wind function values.

input_ffmc: Cube#
moisture_content: ndarray#
wind_speed: Cube#