Abstract

Measuring chlorophyll fluorescence is a direct and non-destructive way to monitor vegetation. In this paper, the fluorescence retrieval methods from multiple scales, ranging from near the ground to the use of space-borne sensors, are analyzed and summarized in detail. At the leaf-scale, the chlorophyll fluorescence is measured using active and passive technology. Active remote sensing technology uses a fluorimeter to measure the chlorophyll fluorescence, and passive remote sensing technology mainly depends on the sun-induced chlorophyll fluorescence filling in the Fraunhofer lines or oxygen absorptions bands. Based on these retrieval principles, many retrieval methods have been developed, including the radiance-based methods and the reflectance-based methods near the ground, as well as physically and statistically-based methods that make use of satellite data. The advantages and disadvantages of different approaches for sun-induced chlorophyll fluorescence retrieval are compared and the key issues of the current sun-induced chlorophyll fluorescence retrieval algorithms are discussed. Finally, conclusions and key problems are proposed for the future research.

Highlights

  • Since the 1980s, vegetation chlorophyll fluorescence has been an effective, non-destructive, and direct way to monitor changes in the physiological state of vegetation [1,2]

  • To extend the near-surface Solar-induced fluorescence (SIF) inversion algorithm to the satellite platform, accurate atmospheric correction information is required in order to obtain fluorescence radiance values

  • F-spectral fitting method (SFM) method, the reflectance is written as a first-order linear expression, and the basis spectra of the SIF spectrum is generated by principal components analysis (PCA)

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Summary

Introduction

Since the 1980s, vegetation chlorophyll fluorescence has been an effective, non-destructive, and direct way to monitor changes in the physiological state of vegetation [1,2]. Since the first global SIF map was produced [33,34,35], many researchers have developed SIF inversion methods from satellite data and have successfully extracted SIF from GOSAT, GOME-2, OCO-2, SCIAMACHY, and TanSat data [36,37,38,39,40,41,42,43]. Meroni et al summarized the sun-induced chlorophyll fluorescence (SIF) retrieval methods including the radiance-based methods and reflectance-based methods and its application at different scales [5]. We summarize the existing problems and conclusions in future research

The Generation of Chlorophyll Fluorescence and Its Spectrum
Active Chlorophyll Fluorescence Measurements
Passive Chlorophyll Fluorescence Measurement
Radiative Transfer Model Inversion
SIF Retrieval Methods in Space Scale
The Principle of Satellite SIF Retrieval Methods
FLD-Like Methods
The Fraunhofer Lines Depth Method
Simplified Radiative Transfer Method
The Statistical Methods
Current Problems and Discussion
The Treatment of Atmospheric Effects
The Zero-Level Offset Correction
Research over the Atmospheric Effects on the Fluorescence Retrieval
Constructing the Fluorescence Validation Network
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