Spectral and diurnal temporal suitability of GOES Advanced Baseline Imager (ABI) reflectance for burned area mapping

Abstract The Advanced Baseline Imager (ABI) onboard the new generation of National Oceanic and Atmospheric Administration (NOAA) Geostationary Operational Environmental Satellite (GOES) series provides 10 min, multi-spectral, 500 m to 2 km observations, with significantly improved capabilities compared to the previous GOES sensors. For the first time GOES data are available with sufficient resolution to potentially enable burned area mapping using the reflective wavelength data. In this study GOES-16 ABI unburned and burned reflectance acquired over four extensive burns in the United States and South America were examined. Significant diurnal variations in the ABI reflectance due to surface reflectance anisotropy and changes in the position of the sun at each ABI observation time were observed, with unburned near-infrared (NIR) reflectance that varied by more than 50% over the day, and this variation was greater than the change in reflectance due to fire. The diurnal reflectance variation included locally increased backscatter reflectance acquired under near hot-spot conditions when the solar zenith was close to the view zenith. The spectral and diurnal temporal suitability of the ABI data for burned area mapping was assessed for the red, NIR and short wave infrared (SWIR) bands using the transformed divergence metric applied to the unburned and burned reflectance values for each ABI acquisition time. The separabilities varied diurnally but with no consistent view-solar geometry or time when the separabilities were consistently high among the four sites. The paper results demonstrate that use of ABI reflectance without consideration of, or correction, for surface anisotropy will be unreliable. The most suitable ABI bands to detect burned areas are the NIR, which provided high diurnal separabilities except in the early morning and late evening, and the normalized burn ratio (NBR), computed as the difference between the NIR and SWIR reflectance divided by their sum, that had more consistently high diurnal separability. Implications and recommendations for future ABI burned area mapping research are discussed.