Retrieval of Terrestrial Plant Fluorescence Based on the In-Filling of Far-Red Fraunhofer Lines Using SCIAMACHY Observations

Abstract

Chlorophyll fluorescence is directly linked to the photosynthetic efficiency of plants. As satellite-based remote sensing has been shown to have the potential to derive global information about fluorescence it has become subject of various recently published studies stimulating an upsurge in this research field. This manuscript presents a simple and fast retrieval method for solar induced terrestrial plant fluorescence (SIF) which relies on only a few prerequisites. The spaced based remote sensing spectrometers used in this work typically exhibit an additive spectral feature, which is not fluorescence. This is often accompanying the actual SIF retrieval and can significantly deteriorate the results. To account for this effect a correction method has been developed and is combined with the retrieval. The method has been applied to 10 years of SCIAMACHY data with promising results. The retrieved SIF values are lying between 0 and 4 mW [m −2 sr −1 nm −1 ]. However, most of the retrieved values are not exceeding 1.5 [m −2 sr −1 nm −1 ], agreeing with previous studies on the subject. Results have been retrieved for SCIAMACHY spatial resolution of 240 30 km 2 × and gridded to 80 arc minutes. A clear seasonal variation could be shown utilizing 10 years of SCIAMACHY data (2002)(2003)(2004)(2005)(2006)(2007)(2008)(2009)(2010)(2011)(2012). In absence of large area ground based validation data a final judgment of the results presented is not feasible. However, a direct comparison to data of others was showing similar results for most areas.

Spaceborne Sun-Induced Vegetation Fluorescence Time Series from 2007 to 2015 Evaluated with Australian Flux Tower Measurements

“…An overview of the algorithm flow is given in Figure 1. In SiF NASA (v26), a first bias correction to SiF maps is made based on retrieved SiF values where zero SiF is expected ( [59]; see also [37] resolution USGS Global Land Cover Characterization database (version 2; https://lta.cr.usgs.gov/GLCC) and if the pixel's effective cloud fraction in the near-infrared is below 0.4. The effective cloud fraction is taken from the FRESCO product [60,61] as included in the GOME-2 radiance product.…”

“…An overview of the algorithm flow is given in Figure 1. In SiF NASA (v26), a first bias correction to SiF maps is made based on retrieved SiF values where zero SiF is expected ( [59]; see also [37]). Figure 2 shows several monthly mean maps that reveal the expected spatial patterns of vegetation activity (four months in 2013).…”

“…These include the Greenhouse gases Observing SATellite (GOSAT) [32][33][34][35], the Global Ozone Monitoring Experiment 2 (GOME-2) [21,36], the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIAMACHY) [33,37], and the Orbiting Carbon Observatory 2 (OCO-2) [38]. Future instruments capable of measuring SiF are the TROPOspheric Monitoring Instrument (TROPOMI) [39] and the dedicated FLuorescence EXplorer mission (FLEX) [40].…”

“…The proposed methods typically require accurate modelling of atmospheric radiative transfer in the absorption bands. A subsequent series of studies showed that filling-in of deep solar Fraunhofer lines can also be used to detect vegetation fluorescence from space [32,33,35,37,43], which in some respects simplifies the retrieval problem. The first maps of global terrestrial fluorescence using filling-in of Fraunhofer lines were achieved with the high-spectral-resolution interferometer aboard GOSAT [32,34,35].…”

New methods for the retrieval of chlorophyll red fluorescence from hyperspectral satellite instruments: simulations and application to GOME-2 and SCIAMACHY

“…Observations of solarinduced fluorescence (SIF) from chlorophyll, obtained from specialized satellites, can provide global coverage within a few days at spatial scales relevant to global models (∼ 0.5 • × 0.5 • grid cells). Satellite instruments that have been utilized to measure chlorophyll SIF over land include the MEdium Resolution Imaging Spectrometer (MERIS) (Guanter et al, 2007), the Japanese Greenhouse gases Observing SATellite (GOSAT) (Joiner et al, 2011(Joiner et al, , 2012Frankenberg et al, 2011b;Guanter et al, 2012), the SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY (SCIA-MACHY) (Joiner et al, 2012;Köhler et al, 2015;Wolanin et al, 2015;Khosravi et al, 2015), the Global Ozone Monitoring Experiment 2 (GOME-2) (Joiner et al, 2013), and the Orbiting Carbon Observatory 2 (OCO-2) (Frankenberg et al, 2014). Terrestrial SIF in the far-red emission peak derived from these satellites has been used for studies focused on tropical dynamics (Parazoo et al, 2013;Guan et al, 2015a), primary productivity (Guanter et al, 2014;Parazoo et al, 2014;Zhang et al, 2014;Lee et al, 2015;Guan et al, 2015b), the carbon uptake period (Joiner et al, 2014;Walther et al, 2015), and responses to drought (Lee et al, 2013;Yoshida et al, 2015;Sun et al, 2015;Wang et al, 2016).…”