![]() ![]() This final index, the fwi, is the component of the System used to establish the daily fire danger level for a region and communicated to the public. The next three outputs of the System are relative (unitless) indicators of aspects of fire behavior potential: spread rate (the Initial Spread Index, isi), fuel consumption (the Build-up Index, bui) and fire intensity per unit length of fire front (the Fire Weather Index, fwi). It is therefore important that when calculating FWI System outputs over an entire fire season, an uninterrupted daily weather stream is provided one day is the assumed time step in the models and thus missing data must be filled in. Their calculation relies on the daily fire weather observation and also, importantly, the moisture code value from the previous day as they are in essence bookkeeping systems tracking the amount of moisture (water) in to and out of the layer. The first three outputs of the system (the Fire Fuel Moisture Code (ffmc), the Duff Moisture Code (dmc), and the Drought Code (dc)) track moisture in different layers of the fuel making up the forest floor. Inputs are a daily noon observation of fire weather, which consists of screen-level air temperature and relative humidity, 10 meter open wind speed and 24 accumulated precipitation. The modern System (Van Wagner 1987) provides six output indices which represent fuel moisture and potential fire behavior in a standard pine forest fuel type. It evolved from field research which began in the 1930's and regional fire hazard and fire danger tables developed from that early research. ![]() The modern FWI System was first issued in 1970 and is the result of work by numerous researchers from across Canada. The Canadian Forest Fire Weather Index (FWI) System is a major subsystem of the Canadian Forest Fire Danger Rating System, which also includes Canadian Forest Fire Behavior Prediction (FBP) System. Output in upper cases or lower cases would be decided by this argument. The function offers options for whether day length adjustments should be applied to the calculations. The function offers two output options, out="all" will produce a data frame that includes both the input and the FWI System outputs out="fwi" will generate a data frame with only the FWI system components. If batch=FALSE, the function calculates only one time step (1 day) base on either the initial start values or the previous day's FWI System variables, which should also be assigned to init argument. If multiple weather stations are processed, an additional "id" column is required in the input to label different stations, and the data needs to be sorted by date/time and "id". When batch=TRUE, the function will calculate daily FWI System outputs for one weather station over a period of time chronologically with the initial conditions given ( init) applied only to the first day of calculation. Whether the computation is iterative or single step, default is TRUE. Latitude of the weather station (optional, default=55). Default value is 6.ĭrought Code (DC unitless) of the previous day. Default value is 85.ĭuff Moisture Code (DMC unitless) of the previous day. Defaults are the standard initial values for FFMC, DMC, and DC defined as the following:įine Fuel Moisture Code (FFMC unitless) of the previous day. The function also accepts a vector if the initial or previous day FWI values is for only one weather station (a warning message comes up if a single set of initial values is used for multiple weather stations). Month of the year (integer 1-12, default=7)ĭay of the month (integer) required when batch=TRUEĪ ame or vector contains either the initial values for FFMC, DMC, and DC or the same variables that were calculated for the previous day and will be used for the current day's calculation. Year of observation required when batch=TRUE Unique identifier of a weather station or spatial point (no restriction on The order in which the input variables are entered is not important. ![]() Variable names have to be the same as in the following list, but they are case insensitive. Usage fwi(input,init=ame(ffmc=85,dmc=6,dc=15,lat=55), batch=TRUE,out= "all",Ī dataframe containing input variables of daily weather observations taken at noon LST. ![]() This function could be used for either one weather station or for multiple weather stations. Fwi is used to calculate the outputs of the Canadian Forest Fire Weather Index (FWI) System for one day or one fire season based on noon local standard time (LST) weather observations of temperature, relative humidity, wind speed, and 24-hour rainfall, as well as the previous day's fuel moisture conditions. ![]()
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