Remote Sensing of Chlorophyll Fluorescence in Oceanography and in Terrestrial Vegetation: An Introduction

Monitoring of water quality changes in highly dynamic inland lakes is frequently impeded by insufficient spatial and temporal coverage, for both field surveys and remote sensing methods. To track short-term variations of chlorophyll fluorescence and chlorophyll-a concentrations in Poyang Lake, the largest freshwater lake in China, high-frequency, in-situ, measurements were collected from two fixed stations. The K-mean clustering method was also applied to identify clusters with similar spatio-temporal variations, using remote sensing Chl-a data products from the MERIS satellite, taken from 2003 to 2012. Four lake area classes were obtained with distinct spatio-temporal patterns, two of which were selected for in situ measurement. Distinct daily periodic variations were observed, with peaks at approximately 3:00 PM and troughs at night or early morning. Short-term variations of chlorophyll fluorescence and Chl-a levels were revealed, with a maximum intra-diurnal ratio of 5.1 and inter-diurnal ratio of 7.4, respectively. Using geostatistical analysis, the temporal range of chlorophyll fluorescence and corresponding Chl-a variations was determined to be 9.6 h, which indicates that there is a temporal discrepancy between Chl-a variations and the sampling frequency of current satellite missions. An analysis of the optimal sampling strategies demonstrated that the influence of the sampling time on the mean Chl-a concentrations observed was higher than 25%, and the uncertainty of any single Terra/MODIS or Aqua/MODIS observation was approximately 15%. Therefore, sampling twice a day is essential to resolve Chl-a variations with a bias level of 10% or less. The results highlight short-term variations of critical water quality parameters in freshwater, and they help identify specific design requirements for geostationary earth observation missions, so that they can better address the challenges of monitoring complex coastal and inland environments around the world.

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SIFSpec: Measuring Solar-Induced Chlorophyll Fluorescence Observations for Remote Sensing of Photosynthesis

Sensors ◽

10.3390/s19133009 ◽

2019 ◽

Vol 19 (13) ◽

pp. 3009 ◽

Cited By ~ 11

Author(s):

Shanshan Du ◽

Liangyun Liu ◽

Xinjie Liu ◽

Jian Guo ◽

Jiaochan Hu ◽

...

Keyword(s):

Remote Sensing ◽

Chlorophyll Fluorescence ◽

Seasonal Variations ◽

Photosynthetic Activity ◽

Gross Primary Production ◽

Atmospheric Correction ◽

Gansu Province ◽

Optical Measurements ◽

Calibration Data ◽

Flux Measurements

Solar-induced chlorophyll fluorescence (SIF) is regarded as a proxy for photosynthesis in terrestrial vegetation. Tower-based long-term observations of SIF are very important for gaining further insight into the ecosystem-specific seasonal dynamics of photosynthetic activity, including gross primary production (GPP). Here, we present the design and operation of the tower-based automated SIF measurement (SIFSpec) system. This system was developed with the aim of obtaining synchronous SIF observations and flux measurements across different terrestrial ecosystems, as well as to validate the increasing number of satellite SIF products using in situ measurements. Details of the system components, instrument installation, calibration, data collection, and processing are introduced. Atmospheric correction is also included in the data processing chain, which is important, but usually ignored for tower-based SIF measurements. Continuous measurements made across two growing cycles over maize at a Daman (DM) flux site (in Gansu province, China) demonstrate the reliable performance of SIF as an indicator for tracking the diurnal variations in photosynthetically active radiation (PAR) and seasonal variations in GPP. For the O2–A band in particular, a high correlation coefficient value of 0.81 is found between the SIF and seasonal variations of GPP. It is thus concluded that, in coordination with continuous eddy covariance (EC) flux measurements, automated and continuous SIF observations can provide a reliable approach for understanding the photosynthetic activity of the terrestrial ecosystem, and are also able to bridge the link between ground-based optical measurements and airborne or satellite remote sensing data.

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Estimating SO2 Stress by Chlorophyll Fluorescence Measurements with an Active System Used in the Remote Sensing Mode

Current Research in Photosynthesis ◽

10.1007/978-94-009-0511-5_816 ◽

1990 ◽

pp. 3611-3614

Author(s):

Cornelis Kliffen

Keyword(s):

Remote Sensing ◽

Chlorophyll Fluorescence ◽

Active System ◽

Fluorescence Measurements

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The Bioindicators of Forest Condition Project: A physiological, remote sensing approach

The Forestry Chronicle ◽

10.5558/tfc76941-6 ◽

2000 ◽

Vol 76 (6) ◽

pp. 941-952 ◽

Cited By ~ 14

Author(s):

Paul H. Sampson ◽

Gina H. Mohammed ◽

Thomas L. Noland ◽

Denzil Irving ◽

Stephen J. Colombo ◽

...

Keyword(s):

Remote Sensing ◽

Chlorophyll Fluorescence ◽

Chlorophyll Content ◽

Spectral Signatures ◽

Condition Rating ◽

Forest Condition ◽

Operational Testing ◽

Level Information ◽

Intensive Sampling ◽

Compact Airborne Spectrographic Imager

Objective measures of forest ecosystem condition are needed to gauge the effects of management activities and natural phenomena on sustainability. The Bioindicators of Forest Condition Project seeks to develop a Forest Condition Rating (FCR) system using a physiological, remote sensing approach. In particular, the goal of the project is to test whether hyperspectral remote sensing may be used to infer stand-level information about pigment concentration, chlorophyll fluorescence, and other physiological features of condition. The project spans a four-year period of intensive sampling in tolerant hardwood forests in Ontario using the Compact Airborne Spectrographic Imager (CASI). For each airborne campaign, concurrent ground-based sampling for leaf physiological features was performed. Controlled laboratory and greenhouse studies were also conducted to derive relationships between leaf-based spectral measurements and physiology in the presence of environmental stresses. The project has identified several promising bioindicators of strain that are discernible from hyperspectral images and related to ground-based physiology. The most promising remote indicator for semi-operational testing is estimation of chlorophyll content, which can be used to classify maple stands on a five-stage scale of health. Chlorophyll fluorescence has also been discerned from spectral signatures, but our studies indicate it may be confounded by chlorophyll content. The intent here is to update the forestry community on progress made, insights gained, and the practical implications of the research. Keywords: chlorophyll fluorescence, hyperspectral, indices, pigments, reflectance, tolerant hardwoods

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On the zero-level offset in the GOSAT TANSO-FTS O<sub>2</sub> A band and the quality of solar-induced chlorophyll fluorescence (SIF): comparison of SIF between GOSAT and OCO-2

Atmospheric Measurement Techniques ◽

10.5194/amt-12-6721-2019 ◽

2019 ◽

Vol 12 (12) ◽

pp. 6721-6735 ◽

Cited By ~ 1

Author(s):

Haruki Oshio ◽

Yukio Yoshida ◽

Tsuneo Matsunaga

Keyword(s):

Chlorophyll Fluorescence ◽

Spatial Scales ◽

Bare Soil ◽

Estimation Accuracy ◽

Terrestrial Vegetation ◽

Analogue Circuit ◽

Zero Level ◽

Global Carbon Budget ◽

Photosynthetic Production

Abstract. Satellite remote sensing of solar-induced chlorophyll fluorescence (SIF) has attracted attention as a method for improving the estimation accuracy of the photosynthetic production of terrestrial vegetation in recent years. The Greenhouse gases Observing Satellite (GOSAT) has the ability to observe both SIF and the concentrations of CO2 and CH4 and thus is expected to contribute to the understanding of the global carbon budget. Evaluating artefact signals (e.g. zero-level offset caused by non-linearity in the analogue circuit in the case of GOSAT) is effective for inferring the instrument status and important for retrieving SIF from satellite measurements. Here we investigate the characteristics of the zero-level offset and the consistency of satellite-derived SIFs by comparing the derived SIF with the Orbiting Carbon Observatory-2 (OCO-2) SIF at multiple spatial scales (footprint to global). The zero-level offset was evaluated using filling-in signals over bare soil while investigating the criteria for identifying barren areas. An analysis of the temporal variation of the zero-level offset over a period of 9 years suggests that the radiometric sensitivity of the GOSAT spectrometer changed after switching the optics path selector in January 2015. The GOSAT SIF was highly consistent with the OCO-2 SIF, with a bias within 0.1 mW m−2 nm−1 sr−1 for most months and an inter-region bias of about 0.2 mW m−2 nm−1 sr−1. Our results agree with the previous comparisons and support the consistency among the present satellite SIF data, which is important for the utilization of those data.

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The Solar-Induced Chlorophyll Fluorescence Imaging Spectrometer (SIFIS) Onboard the First Terrestrial Ecosystem Carbon Inventory Satellite (TECIS-1): Specifications and Prospects

Sensors ◽

10.3390/s20030815 ◽

2020 ◽

Vol 20 (3) ◽

pp. 815 ◽

Cited By ~ 1

Author(s):

Shanshan Du ◽

Liangyun Liu ◽

Xinjie Liu ◽

Xinwei Zhang ◽

Xianlian Gao ◽

...

Keyword(s):

Chlorophyll Fluorescence ◽

Signal To Noise Ratio ◽

Simulated Data ◽

Terrestrial Ecosystem ◽

Global Scale ◽

Terrestrial Vegetation ◽

Atmospheric Transmission ◽

Imaging Spectrometer ◽

Ecosystem Carbon ◽

Carbon Inventory

The global monitoring of solar-induced chlorophyll fluorescence (SIF) using satellite-based observations provides a new way of monitoring the status of terrestrial vegetation photosynthesis on a global scale. Several global SIF products that make use of atmospheric satellite data have been successfully developed in recent decades. The Terrestrial Ecosystem Carbon Inventory Satellite (TECIS-1), the first Chinese terrestrial ecosystem carbon inventory satellite, which is due to be launched in 2021, will carry an imaging spectrometer specifically designed for SIF monitoring. Here, we use an extensive set of simulated data derived from the MODerate resolution atmospheric TRANsmission 5 (MODTRAN 5) and Soil Canopy Observation Photosynthesis and Energy (SCOPE) models to evaluate and optimize the specifications of the SIF Imaging Spectrometer (SIFIS) onboard TECIS for accurate SIF retrievals. The wide spectral range of 670−780 nm was recommended to obtain the SIF at both the red and far-red bands. The results illustrate that the combination of a spectral resolution (SR) of 0.1 nm and a signal-to-noise ratio (SNR) of 127 performs better than an SR of 0.3 nm and SNR of 322 or an SR of 0.5 nm and SNR of 472 nm. The resulting SIF retrievals have a root-mean-squared (RMS) diff* value of 0.15 mW m−2 sr−1 nm−1 at the far-red band and 0.43 mW m−2 sr−1 nm−1 at the red band. This compares with 0.20 and 0.26 mW m−2 sr−1 nm−1 at the far-red band and 0.62 and 1.30 mW m−2 sr−1 nm−1 at the red band for the other two configurations described above. Given an SR of 0.3 nm, the increase in the SNR can also improve the SIF retrieval at both bands. If the SNR is improved to 450, the RMS diff* will be 0.17 mW m−2 sr−1 nm−1 at the far-red band and 0.47 mW m−2 sr−1 nm−1 at the red band. Therefore, the SIFIS onboard TECIS-1 will provide another set of observations dedicated to monitoring SIF at the global scale, which will benefit investigations of terrestrial vegetation photosynthesis from space.

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