1 Fire Weather Science Fire Weather System Project EcoConnect-Fire Implementation, June 2013 April 2011

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Fire Weather ScienceFire Weather System Project

EcoConnect-Fire Implementation, June 2013

April 2011

NZ Fire Danger Rating System

• NZFDRS derived from Canadian equivalent, the CFFDRS

• outputs used to assist decision-making across 4 Rs of fire management

FWISystem

FBPSystem

FOPSystem

New Zealand Fire Danger Rating System

AFMSystem

WeatherRisk ofIgnition

Topography Fuels

NZFDRS

Reduction

Readiness

Recovery

Fire Management Applications

Response

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NZFDRS Outputs

Fire danger rating: “probability of a fire starting, spreading and doing damage”

Fire potential:• indication of expected burning

conditions– ease of ignition– potential spread rates– fire intensity– fire size and shape

• i.e. fire behaviour3

Vegetation Fire Environment

• fire behaviour is the product of the environmental factors which interact with each other and with the fire itself

• i.e., the “fire environment”:– topography– fuel – weather

Weather

Topo

grap

hy

Fuel

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NZ Fire Danger Rating System

NZFDRS actually comprised of a number of subsystems:• Fire Weather Index (FWI) System

core component • fire behaviour and fire danger

classes based on Fire Behaviour Prediction (FBP) System

• Fire Occurrence Prediction (FOP) and Accessory Fuel Moisture (AFM) subsystems still under development

FWISystem

FBPSystem

FOPSystem

New Zealand Fire Danger Rating System

AFMSystem

WeatherRisk ofIgnition

Topography Fuels

NZFDRS

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Fire Weather Index (FWI) System

• numerical ratings of fuel dryness and potential fire behaviour based solely on weather− i.e. considers weather component only

• assumes:− flat ground − uniform fuels − reference fuel type

(dead fuel layers in forest floor beneath mature pine stand)

• provides relative indicators of fire potential

TemperatureRelative Humidity

Wind SpeedRainfall

Wind Speed


RainfallTemperature

Rainfall

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NZ FWI System

• adopted from Canada in 1980− developed in similar fire environment

(British Columbia) to NZ (maritime climate, complex terrain, mature pine fuels)

• adjusted for use in NZ− season reversal for Southern Hemisphere− daylength drying factors for latitude 40°S− year round calculations

• table and computer calculations (incl. new FWSYS)

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FWI System

• 4 weather inputs:− air temperature, relative humidity, wind speed (& wind direction)

and 24-hr accumulated rainfall− measured at 1200 hr NZST

• 3 fuel moisture codes

• 3 fire behaviour indices

• higher code and index values indicate more severe fire potential


Wind SpeedRainfall

Wind Speed


RainfallTemperature

Rainfall

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FWI System – fuel moisture codesIndicators of relative dryness and availability of different fuel layers:

Fine Fuel Moisture Code (FFMC)− moisture content of fine fuels− indicates ease of ignition

Duff Moisture Code (DMC)− moisture content of loose organic

layers & medium woody fuels− involvement of duff & woody fuels

Drought Code (DC)− moisture content of compact organic layers & large fuels− involvement of deep organic fuels− indicates potential for mop-up problems, and general seasonal dryness 9


Wind SpeedRainfall

Wind Speed


RainfallTemperature

Rainfall

FWI System – fire behaviour indices Relative indicators of potential fire behaviour:

Initial Spread Index (ISI)− combines FFMC and wind speed− indicates potential spread rate

Buildup Index (BUI)− combines DMC & DC− indicates total fuel consumption

Fire Weather Index (FWI)− combines ISI & BUI− indicates potential fire intensity

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Wind SpeedRainfall

Wind Speed


RainfallTemperature

Rainfall

Fire Behaviour Prediction (FBP) System

• quantitative estimates of fire behaviour based on fuels, topography and weather

• predictions of:− fire spread rates− fuel consumption− fire intensity− fire area & perimeter length− perimeter growth

• assumes elliptical fire growth

Primary outputs:Head fire rate of spread, Fuel load/consumption,

Head fire intensity,



Secondary outputs:Spread distances,

Flank & back fire ROS & I, Area, Perimeter,

PGR and L/B ratio



PGR and L/B ratio

FuelsFuels WeatherWeather TopographyTopographyFoliar

moisturecontent

Foliarmoisturecontent

Type &duration ofprediction


Fire Behaviour Prediction(FBP) System


FBP SystemFuel Type

FFMC, ISI & BUI,

Wind speed& direction

Slope angle&

Aspect

Elevation,Lat./Long.,

Date

Elapsed time,Point or Line

ignition







PGR and L/B ratio



PGR and L/B ratio

FuelsFuels WeatherWeather TopographyTopographyFoliar

moisturecontent

Foliarmoisturecontent





FBP SystemFuel Type

FFMC, ISI & BUI,

Wind speed& direction

Slope angle&

Aspect

Elevation,Lat./Long.,

Date

Elapsed time,Point or Line

ignition

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NZ FBP System

• currently 18 identified fuel types − 6 plantation forest− 2 indigenous forest− 2 pasture grassland− 2 crop stubble− 2 tussock grassland− 4 scrub

• models for:− available fuel loads− fire spread rates− slope correction factors

• various tools now available12

NZ Fire Danger Class Criteria

• combines FWI & FBP Systems • fire danger classes based

on head fire intensity (HFI)• related to suppression

effectiveness• models available for Forest,

Grassland and Scrubland from FBP System

• principal use for notifying the public

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Fire Danger Class Limits

FireDangerClass

FireIntensity(kW/m)

ControlRequirements

L < 10 Ground crews with handtools

M 10-500 Ground crews with back-pack pumps

H 500-2000 Water under pressureand/or heavy machinery

VH 2000-4000 Aircraft using chemicalfire retardants

E > 4000 Very difficult if notimpossible to control

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NZ Fire Danger Class CriteriaTemperature

Relative HumidityWind Speed

RainfallWind Speed


RainfallTemperature

Rainfall

Scrubland GrasslandForestScrubland Fire Danger Class Graph

0

10

20

30

40

50

60

50 60 70 80 90 100

Fine Fuel Moisture Code (FFMC)

10-m

Ope

n W

ind

Spe

ed (

km/h

)

Low

Extreme

Very High

High

Moderate

Grassland Fire Danger Class Graph

0

5

10

15

20

25

30

50 60 70 80 90 100

Degree of Curing (%)

Init

ial

Spr

ead

Inde

x (I

SI)

Low

Moderate

High

Very High

Extreme

Forest Fire Danger Class Graph

0

5

10

15

20

25

30

0 20 40 60 80 100 120

Buildup Index (BUI)

Init

ial

Spr

ead

Inde

x (I

SI)

Low

Moderate

High

Very High

Extreme

Grass Degree of Curing (%)

Wind speed

FFMC

ISIISI

BUI DoC%15

New EcoConnect FWSYS

Incorporates latest fire behaviour knowledge: • new wind speed-Initial Spread

Index (ISI) relationship– reduced effect at high

wind speeds (>40 km/h)

• new grass degree of curing (DoC%) relationship– allows for limited fire spread

below DoC of 50%

• also able to incorporate future new science (e.g. FWI, curing)

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Daily vs Hourly FWI Values

0

2

4

6

8

10

12

14

16

18

20

22

24

0 3 6 9 12 15 18 21 24

Local Standard Time

Te

mp

era

ture

(oC

); W

ind

Sp

ee

d (

km

/h)

0

10

20

30

40

50

60

70

80

90

100

Darfield (FPL)

Re

lati

ve

Hu

mid

ity

(%

)

Temperature

Wind Speed

Relative Humidity

Standard daily FWI System calculations include in-built diurnal forecasting • uses 1200 NZST observations

but predicts for peak burning period (1600 hr)

• assumes standard diurnal weather pattern– doesn’t always hold,

e.g. frontal change, sea breeze

• hourly FWIs more accurate– based on actual hourly weather– hourly FWIs in new FWSYS coming!

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Conclusions

• NZFDRS provides outputs that assist fire management decision-making

• NZFDRS is more than just the FWI System– FWI is core, but also FBP and FDCC

• Noon daily FWI predicts for mid-afternoon peak burning period (1600 hr)– but assumes standard diurnal cycle, will not always be valid

• New EcoConnect-Fire package provides key tool for accessing important fire weather outputs – includes latest science, will be updated as new results produced

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Documents

1 Fire Weather Science Fire Weather System Project EcoConnect-Fire Implementation, June 2013 April 2011