Inferring gross primary productivity from TROPOMI SIF

Abstract:

Solar-Induced chlorophyll Fluorescence (SIF) has been shown to be a powerful proxy for canopy-scale photosynthesis and gross primary productivity (GPP). The recently launched TROPOspheric Monitoring Instrument (TROPOMI) features the required spectral resolution and signal-to-noise ratio to retrieve SIF from space. Here we present work building a parsimonious relationship between daily measurements of SIF from TROPOMI and GPP from AmeriFlux across ecosystems. We use a Gaussian mixture model to identify distinct relationships between SIF and GPP. The mixture model indicates that the SIF-GPP relationship can be characterized by a linear model comprised of four scaling factors. We combine this with recent work downscaling SIF to produce daily 500-m GPP over CONUS (daily values reflect averages over a 16-day window). Finally, we highlight interannual variations in TROPOMI-derived GPP that correspond to environmental stressors including: drought in California, flooding in the Midwest, and drought in Texas.