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* Metric Name: Mean Percent FRI Departure, Since 1908  

* Tier: 3  

* Data Vintage: 2022. Includes disturbances through the end of 2022  

* Unit Of Measure: Percent (-100% to 100%), departure from mean FRI  

* Represent element and pillar: No  

* Type and distribution of data: Left-skewed, beta-like distribution representing percentages. Raw data values range from –95.290 to 90.430.  

* Translation: Where is the fire return interval within the historical range?  

* Translation method and outcome: Raw data values translated to range from +1 to -1 representing more favorable to less favorable conditions, respectively. **** The proposition of more favorable is based on the objective of being within 33% (more or less frequent) of the average historical fire return interval. More favorable (translated to +1) set at –33 to +33% of fire return interval, less favorable (translated to -1) set at < -67% for too frequent fire, and >67% for too infrequent fire, based on FRID condition classes. 

Figure . Histogram and scoring criterion of mean percent fire return interval
departure, since 1908 across the Central Coast.

Figure . Histogram of translated current mean percent fire return interval
departure, since 1908 across the Central Coast.

Figure . Maps displaying raw metric and translated metric of mean percent fire
return interval departure, since 1908 across the Central Coast.

  

* Metric Definition and Relevance: This metric, mean percent FRID, is a measure of the extent to which contemporary fires (i.e., since 1908) are burning at frequencies similar to the frequencies that occurred prior to Euro-American settlement, with the mean reference FRI as the basis for comparison. Mean PFRID is a metric of fire return interval departure (FRID) and measures the departure of current FRI from reference mean FRI in percent.  

* Credits: Fire History (2022), CAL FIRE Existing Vegetation (CALVEG 2011), USDA Forest Service, Region 5, MARS Team