Characterizing fire and fire atmospheric states from space using collocated hyperspectral infrared sounding and narrow-band imagery

Under the influence of global climate change, wildfires are becoming increasingly significant within ecosystems. Satellite technology offers a critical perspective for studying fire. The synergy of high-spatial resolution narrow-band imagers and hyperspectral infrared (IR) sounders allow for comprehensive observation and long-term global monitoring of fire characteristics and associated atmospheric changes on the pixel scale. This study demonstrates methods to utilize the pixel-scale collocated fire observations from the Visible Infrared Imaging Radiometer Suite (VIIRS) and the IR radiance spectra from the Cross Track Infrared Sounder (CrIS), onboard NASA's Suomi National Polar-orbiting Partnership (SNPP) satellite, to analyze fire and the atmospheric conditions before, during, and after fires. Two months of satellite observations over the Southwest United States and the Amazonia regions when large fires occurred in the regions of interest (October 2017 and August 2020) are used. Our findings reveal that CrIS has high sensitivity to fire that affects as little as 1% of its field of view (FOV) with FOV total fire radiative power (FRP) larger than 200 MW (MW) at night and 1000 MW during the day. By employing spectral principal component analysis (PCA), the CrIS spectral signature to atmospheric temperature, humidity, and trace gases corresponding to fire characteristics are quantified. This approach highlights that collocated imager and IR sounder data, when paired with PCA, provide a powerful method to effectively identify and monitor wildfires. This technique also allows for the observation of subsequent atmospheric alterations while managing data volume efficiently, ensuring that crucial spectral information is preserved. This methodology advances our ability to understand and respond to the multifaceted impacts of wildfires on both local and global scales, reinforcing the value of integrated satellite observations in environmental science.