FLEX-based inferring of terrestrial photosynthesis dynamics for quantifying European vegetation productivity

Introduction

Photosynthesis, the biochemical process by which vegetation harvests sunlight to convert carbon dioxide and water into carbohydrates and O2, fuels all life on Earth and drives the global carbon cycle. Although the majority of absorbed light is used for carbon assimilation, a remaining part is lost as heat and dissipated as emissions of solar-induced chlorophyll fluorescence (SIF).

Understanding SIF

SIF, the radiant flux emitted between 650 and 800 nm, is therefore the most direct measurable reporter of photosynthetic machinery in plants. Dedicated to retrieving the full SIF signal emitted across the globe, ESA has selected the FLuorescence EXplorer (FLEX) mission concept as Earth Explorer 8.

FLEX Mission Overview

To be launched in 2024, FLEX will fly in tandem with Copernicus’ Sentinel-3 (S3) and will operate at ideal spectral, spatial, and temporal resolutions. We are only at the dawn of uncovering the full SIF potential from space, as so far only a few single SIF bands have been exploited.

Key Challenges

The key challenge in the upcoming FLEX era will be to explore this unique new source of information and link it to photosynthetic activity.

FLEXINEL Proposal

This proposal - named FLEXINEL - is determined to take leadership in exploiting and interpreting the forthcoming FLEX data stream targeting European vegetation productivity and carbon fluxes monitoring. This will be achieved given the state of the art in:

1. Plant physiology
2. Leaf-canopy-atmosphere radiative transfer mechanisms
3. Machine learning
4. Image processing

Advancing Science

FLEXINEL seeks to advance the science in consolidating relationships between SIF products and complementary S3 vegetation traits, thereby uncovering the role of dynamic vegetative and atmospheric variables given a changing Earth.

Methodology

Together with physically-based modelling, the latest image processing concepts will be applied, such as emulation and cloud computing. FLEX and S3 products will be fed into assimilation systems for quantifying photosynthesis dynamics, and into an operational biosphere model for improving Europe-to-global carbon flux estimation.