The Diurnal Dynamics of Gross Primary Productivity Using Observations From the Advanced Baseline Imager on the Geostationary Operational Environmental Satellite‐R Series at an Oak Savanna Ecosystem

• Published in: Journal of geophysical research. Biogeosciences Vol. 127; no. 3
• Main Authors: Khan, A. M., Stoy, P. C., Joiner, J., Baldocchi, D., Verfaillie, J., Chen, M., Otkin, J. A.
• Format: Journal Article
• Language: English
• Published: 01.03.2022
• ISSN: 2169-8953; 2169-8961
• DOI: 10.1029/2021JG006701

Gross primary productivity (GPP) is the largest flux in the global carbon cycle and satellite‐based GPP estimates have long been used to study the trends and interannual variability of GPP. With recent updates to geostationary satellites, we can now explore the diurnal variability of GPP at a comparable spatial resolution to polar‐orbiting satellites and at temporal frequencies comparable to eddy covariance (EC) tower sites. We used observations from the Advanced Baseline Imager on the Geostationary Operational Environmental Satellite‐R series (GOES‐R) to test the ability of subdaily satellite data to capture the shifts in the diurnal course of GPP at an oak savanna EC site in California, USA that is subject to seasonal soil moisture declines. We compared three methods to estimate GPP: (a) a light‐use efficiency model, (b) a linear relationship between the product of near‐infrared reflectance of vegetation and photosynthetically active radiation (LIN‐NIRvP) and EC tower GPP, and (c) a light response curve (LRC‐NIRvP) between NIRvP and EC GPP. The LRC‐NIRvP achieved the lowest mean absolute error for winter (2 µmol CO2 m−2 s−1), spring (2.51 µmol CO2 m−2 s−1), summer (1.43 µmol CO2 m−2 s−1), and fall (1.35 µmol CO2 m−2 s−1). The ecosystem experienced the largest shift in daily peak GPP in relation to the peak of incoming solar radiation toward the morning hours during the dry summers. The LRC‐NIRvP and the light‐use efficiency model were in agreement with these patterns of a shift in peak daily GPP toward the morning hours during summer. Our results can help develop diurnal estimates of GPP from geostationary satellites that are sensitive to fluctuating environmental conditions during the day. Plain Language Summary Gross primary productivity (GPP) quantifies the drawdown of atmospheric CO2 through ecosystem‐scale photosynthesis. Large‐scale estimates of GPP are a crucial component of carbon cycle science and can be estimated using satellites. Motivated by the recent advances in the spectral coverage and spatial resolution of geostationary (“weather”) satellites, we demonstrate how the Advanced Baseline Imager (ABI) on the Geostationary Operational Environmental Satellite‐R series can provide satellite‐based, half‐hourly GPP estimates at the Tonzi Ranch Ameriflux eddy covariance site in California, USA. We found that a light response curve is able to achieve the best agreement between ABI‐based estimates of GPP and GPP partitioned from gas exchange measurements at the eddy covariance site. Previous research has demonstrated that the diurnal peak of GPP shifts increasingly toward the morning at Tonzi Ranch as the year progresses into the dry season. We found that ABI can capture this characteristic seasonal shift of peak diurnal GPP, which highlights its ability to measure ecosystem dynamics in addition to the weather patterns that help cause them. Key Points The Geostationary Operational Environmental Satellite‐R Series can estimate gross primary productivity every half hour A light response curve provides the best agreement with gross primary productivity estimated at an Ameriflux oak savanna site Diurnal satellite‐based estimates of gross primary productivity follow the shift toward the mornings during the dry summers at the site