Analysis of Satellite Data for Use in Grassland Fire Danger Indices

Grassland and rangeland wildfires can have significant and lasting effects on both the natural and built environment. These wildfires are responsible for devastating swaths of damage left behind—culminating in considerable losses in grassland and rangeland as well as homes and infrastructure. Wildfires are especially common in the Great Plains region fueled by strong winds and low humidity when in the presence of dry grasses or shrubs. NOAA’s Grassland Fire Danger Index (GFDI) was developed to estimate the level of fire danger in the Great Plains from meteorological data and estimates of the vegetation moisture content. The Curing Index, the variable in the GFDI which indicates the percentage of moisture within vegetation, is currently estimated with several methods. This study compares a meteorological method, the Growing Season Index (GSI), with a satellite-derived Green Vegetation Fraction (GVF). The GVF is derived from GOES ABI (Advanced Baseline Imager) data on a weekly basis and interpolated daily to be compared with the daily GSI from March through October during 2021-2022. Estimates of the GFDI using both the GSI and GVF to derive the Curing Index were calculated at selected Remote Automated Weather Stations (RAWS) located within either grassland or shrubland vegetation. Grassland RAWS GFDI calculated from GSI had more days classified as “high” fire danger levels. There were more differences between GSI- and GVF-derived GFDI in the summer that were attributed to the peak in the Vapor Pressure Deficit that is included in the derivation of the GSI. The Curing Index derived from GSI also demonstrated a Fall green-up that is not typically observed during this wildfire season. We conclude that satellite-derived products may be useful in combination with the GSI to provide more accurate estimates of the Curing Index component of the GFDI.