Motivation: To understand the complex ways that terrestrial ecosystems are responding and feeding back to the changing global environment, we need to figure out how to use satellite data to accurately diagnose the patterns and determinants of photosynthesis and respiration across the Earth’s surface.

Background: Currently, there are dozens of satellite-driven estimates of terrestrial photosynthesis and respiration, but all (a) do require calibration to surface observations of meteorology and/or eddy covariance, and (b) do not permit separation of the environmental versus physiological controls on photosynthesis and respiration.

Approach: With support from NASA’s New (Early Career) Investigator Program, I am developing a process-based model of canopy-level photosynthesis that links the absorption of light and emission of fluorescence (which are accessible via proximal and remote sensing) to the turbulent exchanges of heat, water vapor, and carbon dioxide (which are accessible via eddy covariance). The core of this model is a description of photosynthesis which fully closes the leaf energy, mass, and charge balances, and is described in more detail in the PHYSIOLOGY section.

The full story: The goal is to be able to parameterize the final model purely from satellite data and couple it into frameworks that are used for numerical simulation of the Earth system. But for now, the model is a work-in-progress!

Significance: Eventually, applications of this framework are expected to advance understanding of vegetation dynamics, land-atmosphere coupling, and carbon-climate feedbacks. In NASA’s most recent decadal survey, these are among the most important objectives for research in ecosystem change (E-1, E-2, E-3), coupling of the water and energy cycles (H-1, H-2), extending and improving weather and air quality forecasts (W-1), and reducing climate uncertainty and informing societal response (C-1).