Systematic Orbital Geometry-Dependent Variations in Satellite Solar-Induced Fluorescence (SIF) Retrievals

While solar-induced fluorescence (SIF) shows promise as a remotely-sensed measurement directly related to photosynthesis, interpretation and validation of satellite-based SIF retrievals remains a challenge. SIF is influenced by the fraction of absorbed photosynthetically-active radiation at the canopy level that depends upon illumination geometry as well as the escape of SIF through the canopy that depends upon the viewing geometry. Several approaches to estimate the effects of sun-sensor geometry on satellite-based SIF have been proposed, and some have been implemented, most relying upon satellite reflectance measurements and/or other ancillary data sets. These approaches, designed to ultimately estimate intrinsic or physiological components of SIF related to photosynthesis, have not generally been applied globally to satellite measurements. Here, we examine in detail how SIF and related reflectance-based indices from wide swath polar orbiting satellites in low Earth orbit vary systematically due to the host satellite orbital characteristics. We compare SIF and reflectance-based parameters from the Global Ozone Mapping Experiment 2 (GOME-2) on the MetOp-B platform and from the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel 5 Precursor satellite with a focus on high northern latitudes in summer where observations at similar geometries and local times occur. We show that GOME-2 and TROPOMI SIF observations agree nearly to within estimated uncertainties when they are compared at similar observing geometries. We show that the cross-track dependence of SIF normalized by PAR and related reflectance-based indices are highly correlated for dense canopies, but diverge substantially as the vegetation within a field-of-view becomes more sparse. This has implications for approaches that utilize reflectance measurements to help account for SIF geometrical dependences in satellite measurements. To further help interpret the GOME-2 and TROPOMI SIF observations, we simulated cross-track dependences of PAR normalized SIF and reflectance-based indices with the one dimensional Soil-Canopy Observation Photosynthesis and Energy fluxes (SCOPE) canopy radiative transfer model at sun–satellite geometries that occur across the wide swaths of these instruments and examine the geometrical dependencies of the various components (e.g., fraction of absorbed PAR, SIF yield, and escape of SIF from the canopy) of the observed SIF signal. The simulations show that most of the cross-track variations in SIF result from the escape of SIF through the scattering canopy and not the illumination

Systematic Orbital Geometry-Dependent Variations in Satellite Solar-Induced Fluorescence (SIF) Retrievals

While solar-induced fluorescence (SIF) shows promise as a remotely-sensed measurement directly related to photosynthesis, interpretation and validation of satellite-based SIF retrievals remains a challenge. SIF is influenced by the fraction of absorbed photosynthetically-active radiation at the canopy level that depends upon illumination geometry as well as the escape of SIF through the canopy that depends upon the viewing geometry. Several approaches to estimate the effects of sun-sensor geometry on satellite-based SIF have been proposed, and some have been implemented, most relying upon satellite reflectance measurements and/or other ancillary data sets. These approaches, designed to ultimately estimate intrinsic or physiological components of SIF related to photosynthesis, have not generally been applied globally to satellite measurements. Here, we examine in detail how SIF and related reflectance-based indices from wide swath polar orbiting satellites in low Earth orbit vary systematically due to the host satellite orbital characteristics. We compare SIF and reflectance-based parameters from the Global Ozone Mapping Experiment 2 (GOME-2) on the MetOp-B platform and from the TROPOspheric Monitoring Instrument (TROPOMI) on the Sentinel 5 Precursor satellite with a focus on high northern latitudes in summer where observations at similar geometries and local times occur. We show that GOME-2 and TROPOMI SIF observations agree nearly to within estimated uncertainties when they are compared at similar observing geometries. We show that the cross-track dependence of SIF normalized by PAR and related reflectance-based indices are highly correlated for dense canopies, but diverge substantially as the vegetation within a field-of-view becomes more sparse. This has implications for approaches that utilize reflectance measurements to help account for SIF geometrical dependences in satellite measurements. To further help interpret the GOME-2 and TROPOMI SIF observations, we simulated cross-track dependences of PAR normalized SIF and reflectance-based indices with the one dimensional Soil-Canopy Observation Photosynthesis and Energy fluxes (SCOPE) canopy radiative transfer model at sun–satellite geometries that occur across the wide swaths of these instruments and examine the geometrical dependencies of the various components (e.g., fraction of absorbed PAR, SIF yield, and escape of SIF from the canopy) of the observed SIF signal. The simulations show that most of the cross-track variations in SIF result from the escape of SIF through the scattering canopy and not the illumination

Providing flexible tradeoff for provenance tracking

The description of the origins of a piece of data and the transformations by which it arrived in a database is called data provenance, lineage or pedigree. The two major approaches to represent provenance information use annotations and inversion. Annotations are flexible in representing diverse provenance metadata but the complete provenance data may outsize the data itself. The inversion method is concise by using a single inverse query or function but the provenance needs to be computed on-the-fly which can be expensive. This paper proposes a new approach of provenance storage which combines the two methods and is adaptive to storage constraint

Scaling analysis, correlation length and compaction estimates of natural and simulated stylolites

International audienceStylolites are rough dissolution surfaces that show three different scaling regimes in space and time. On the small scale surface energy dominates and stylolites roughen very slowly with a growth exponent of about 0.5 and a roughness exponent of about 1.0. On the intermediate scale elastic energy dominates and the surfaces roughening is happening faster with a growth exponent of about 0.8 and a roughness exponent of about 0.5. The transitional length between these two scaling regimes is determined by the stress during stylolite growth and termed as cross-over length scale. On the large scale another transition is reached beyond which the stylolite amplitude remains constant, this length scale is termed the correlation length. The correlation length is determined by time of growth or by the amount of compaction that happened at the interface as well as by the stylolite's system size. This length scale grows as a function of time and the dynamic exponent, which is about 2 in the surface energy dominated regime and 0.625 in the elastic energy dominated regime. We present examples of these scaling regimes for numerical as well as natural stylolites and show how the exponents can be used to determine the stylolite compaction through the different regimes. The numerical stylolites show an increase of correlation length as a function of system size in self-affine time series. Large samples of natural tectonic stylolites from Jurassic limestones of the Franconian Alb (SE Germany) exhibit all three scaling regimes in a self-affine space series. The important length scales in the natural system are the grain size or noise at 30 μm, the cross-over length between the surface and elastic energy dominated regimes at 1.4 mm and the correlation length at 5.7 cm. The overall compaction on the tectonic stylolite is estimated to be in the range of 8 cm