High-resolution Fire Weather Index projections are now available for physical risk assessments and climate impact studies. They are available for 5 Earth System Models and 3 emissions scenarios (or Shared Socioeconomic Pathways, SSP1-2.6, SSP2-4.5 and SSP5-8.5) at a spatial resolution of 0.1°x0.1° (about 10 km x 10 km) worldwide and are ow part of our Ready-to-use climate projections.
The Fire Weather Index (FWI) is a weather variable based index used around the world to estimate fire danger. It accounts for the effects of fuel moisture and wind on fire behavior and spread. The higher the FWI is, the more favorable the meteorological conditions to trigger a wildfire are. Its indicators are at the base or the high-resolution Wildfire Risk projections. The FWI and other FWI derived indices (danger classes, fire risk days, fire season length etc.) can be used to evaluate future wildfire risk conditions.
The FWI used here is the Canadian Forest Fire Weather Index system. It is composed of several model components that account for the effects of the moisture content of the forest floor and weather conditions on fire behavior. It is calculated from five daily weather variables: temperature, relative humidity, wind speed, and 24-hour precipitation.
There are three widely used fire risk weather based models developed in Canada (FWI), the USA (U.S. Forest Service National Fire-Danger Rating System), and Australia (McArthur Mk5 Forest Fire Danger Meter). The European Forest Fire Information System (EFFIS) network and The Global Wildfire Information System (GWIS) adopted the Canadian Forest Fire Weather Index (FWI) as the reference for operational fire danger forecasts (they recently included the other two for comparison purposes). So did the Copernicus Emergency Management Service for the historical data. For the Future risk assessment, the Copernicus Climate Change Service also selected the Canadian Index as it is the reference for the EFFIS/GWIS. In short the Canadian, US and Australian national administrations use their own Fire Index while in Europe authoritative institutions adopted the Canadian model as reference. In the US, NASA also adopted the Canadian Index for global applications. The FWI used here can thus be directly compared to operational FWI products used elsewhere, especially the EFFIS system.
FWI values for present climate (1991-2020) are calculated using data from the ERA5-Land reanalysis. A reanalysis is produced by combining weather models with observations to provide a comprehensive description of recent global climate. The ERA5-Land dataset is provided by the Copernicus Climate Change Services (C3S) and is a world reference for historical climate analysis.
FWI values for future climate by the end of the century are calculated using data from high-resolution climate projections. Those are obtained by statistical techniques called “downscaling” that combine reanalysis data and climate model simulations to increase the spatial resolution of the original climate model data (from hundreds of kilometers to tens of kilometers). We recently produced a high-resolution climate projections dataset based on the latest IPCC climate simulations that is coherent with the ERA5-Land reanalysis. This allows to have future values of FWI that are coherent with the historical FWI series.
The Fire Weather Index projections are now part of our Ready-to-use climate projections IPCC AR6/CMIP6 based variables, indicators and hazards.
