Monitoring Ecosystem Disturbance and Carbon Flux Using Observations from the Advanced Baseline Imager on the Geostationary Operational Environmental Satellite

Abstract:

Environmental science is increasingly reliant on remotely-sensed observations of the Earth’s surface and atmosphere. Observations from polar orbiting satellites have long supported investigations on land cover change, ecosystem productivity, the impacts of disturbance, hydrology, climate, and more, and are critical for extrapolating ground-based measurements and models to larger areas. However, the temporal frequency at which polar orbiting satellites observe the Earth limits our understanding of rapidly evolving ecosystem processes, especially in areas with frequent cloud cover. Geostationary satellites have been observing the Earth’s surface and atmosphere at high temporal frequency for decades, and recent advances in geostationary imagers have resulted in increased spectral resolution in the visible and near-infrared regions such that they are now comparable to polar orbiting satellites. Despite this, geostationary satellites are rarely used for environmental science and in some cases it is unclear if the ‘hyper-temporal’ observations (on time scales of minutes) represent an improvement over polar-orbiting overpasses on time scales of days. Here, we track changes in the Normalized Difference Vegetation Index (NDVI) during the 2019 Kincade Fire in California on 5-minute timescales using top-of-atmosphere (TOA) reflectances from the Advanced Baseline Imager (ABI) on the Geostationary Operational Environmental Satellite (GOES) and the Moderate Resolution Imaging Spectroradiometer (MODIS). From March 1, 2019 to March 31, 2020, an increased number of days had cloud-free observations available from ABI (307 days) compared to MODIS (186 days). We find that TOA NDVI calculated from ABI Level 2 Cloud and Moisture Imagery and Level 1B MODIS data (Terra and Aqua) followed a similar annual pattern inside and outside of the fire perimeter. However, MODIS TOA NDVI exhibited high daily fluctuation around the ABI midday median TOA NDVI. We then use satellite-derived measurements of solar radiation, NDVI and local temperature measurements to demonstrate the applicability of ABI observations for carbon cycle monitoring as a complement to MODIS-based approaches. Geostationary satellites can enrich our understanding of land surface processes and help usher in the era of hyper-temporal remote sensing.