Abstract
Abstract. Global monitoring of sun-induced chlorophyll fluorescence (SIF) is improving our knowledge about the photosynthetic functioning of terrestrial ecosystems. The feasibility of SIF retrievals from spaceborne atmospheric spectrometers has been demonstrated by a number of studies in the last years. In this work, we investigate the potential of the upcoming TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor satellite mission for SIF retrieval. TROPOMI will sample the 675–775 nm spectral window with a spectral resolution of 0.5 nm and a pixel size of 7 km × 7 km. We use an extensive set of simulated TROPOMI data in order to assess the uncertainty of single SIF retrievals and subsequent spatio-temporal composites. Our results illustrate the enormous improvement in SIF monitoring achievable with TROPOMI with respect to comparable spectrometers currently in-flight, such as the Global Ozone Monitoring Experiment-2 (GOME-2) instrument. We find that TROPOMI can reduce global uncertainties in SIF mapping by more than a factor of 2 with respect to GOME-2, which comes together with an approximately 5-fold improvement in spatial sampling. Finally, we discuss the potential of TROPOMI to map other important vegetation parameters at a global scale with moderate spatial resolution and short revisit time. Those include leaf photosynthetic pigments and proxies for canopy structure, which will complement SIF retrievals for a self-contained description of vegetation condition and functioning.
Highlights
Sun-induced chlorophyll fluorescence (SIF) is an electromagnetic signal emitted by the chlorophyll a of assimilating plants: part of the energy absorbed by chlorophyll is not used for photosynthesis, but emitted at longer wavelengths as a two-peak spectrum roughly covering the 650–850 nm spectral range (Porcar-Castell et al, 2014)
In this paper we present a sensitivity analysis showing the potential of TROPOspheric Monitoring Instrument (TROPOMI) for SIF retrieval
In this paper we have discussed the potential of the upcoming Sentinel-5 Precursor mission (S5P)/TROPOMI for global monitoring of SIF
Summary
Sun-induced chlorophyll fluorescence (SIF) is an electromagnetic signal emitted by the chlorophyll a of assimilating plants: part of the energy absorbed by chlorophyll is not used for photosynthesis, but emitted at longer wavelengths as a two-peak spectrum roughly covering the 650–850 nm spectral range (Porcar-Castell et al, 2014). It must be remarked that TROPOMI will be the first imaging spectrometer ever to deliver global data with a moderate spatial resolution and a continuous spectral sampling of the red and NIR spectral regions (the so-called vegetation red-edge), which are covered by GOME-2 and SCIAMACHY but with a much coarser spatial resolution This wide spectral sampling will potentially make it possible to exploit the information carried by the full SIF spectrum and by the longer wavelength peak at the NIR (see Fig. 1). It typically takes values between 4 and 10 depending on the width of the fitting window and the amount of solar and atmospheric lines contained in it
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