Global data and information about wildfires is fragmented and inconsistent in many areas of the world. Global burned area products derived from satellite imagery provide information on spatial and temporal attributes of all areas affected by fires, but they do not contain information on single wildfire events. This fact makes it impossible to distinguish certain wildfire types or study their behavior or occurrence based on the dynamics of individual events.
The data provided and displayed in GWIS is derived following the Globfire methodology. GlobFire uses the MODIS burned area product (MCD64A1) to define wildfire events and compute the burnt area of each event. Burnt areas at country (or any other Administrative level) are derived by the adding the burnt areas of the single fire events.
The MCD64A1 product combines imagery from Terra and Aqua, along with thermal anomalies, and provides burning and quality information on a per-pixel basis (more details may be accessed at https://modis-land.gsfc.nasa.gov/burn.html & http://modis-fire.umd.edu/files/MODIS_C6_BA_User_Guide_1.2.pdf).
This GWIS Globfire data are not provided in real time, as the base MCD64A1 product takes approximately two months be available (see temporal granularity of the source product https://lpdaac.usgs.gov/dataset_discovery/modis/modis_products_table/mcd64a1_v006). Initial and final dates of the fires are subject to an uncertainty of few days.
Currently, GWIS displays data from 2001 to February 2018.
Artés, T., Oom, D., de Rigo, D., Houston-Durrant, T, Maianti, P., Liberta, G., San-Miguel-Ayanz, J. (2019) A global wildfire dataset for the analysis of fire regimes and fire behaviour. Sci Data 6, 296 https://doi.org/10.1038/s41597-019-0312-2
Burnt area information generated in the GWIS NRT product is based on the combined used of thermal anomalies from MODIS and VIIRS sensors for delineating single fire perimeters, which are then used to estimate the burnt area caused by the fires. GWIS uses the active fire detection provided by the NASA FIRMS (Fire Information for Resource Management System).
MODIS Active fires
The MODIS sensor, on board the TERRA and ACQUA satellites, identifies areas on the ground that are distinctly hotter than their surroundings and flags them as active fires. The difference in temperature between the areas that are actively burning with respect to neighbouring areas allows active fires to be identified and mapped. The spatial resolution of the active fire detection pixel from MODIS is 1 km.
Additional information on the MODIS active fire product is available at https://earthdata.nasa.gov/what-is-new-collection-6-modis-active-fire-data
VIIRS Active fires
The VIIRS (Visible Infrared Imaging Radiomer Suite) on board the NASA/NOAA Suomi National Polar-orbiting Partnership (SNPP) uses similar algorithms to those used by MODIS to detect active fires. The VIIRS active fire products complements the MODIS active fire detection and provides an improved spatial resolution, as compared to MODIS. The spatial resolution of the active fire detection pixel for VIIRS is 375 m. Additionally, VIIRS is able to detect smaller fires and can help delinate perimeters of ongoing large fires.
Additional information on VIIRS active fire products can be found at https://earthdata.nasa.gov/earth-observation-data/near-real-time/firms/viirs-i-band-active-fire-data