Potential of the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor for the monitoring of terrestrial chlorophyll fluorescence

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

Plasticity reveals hidden resistance to extinction under climate change in the global hotspot of salamander diversity

Extinction rates are predicted to rise exponentially under climate warming, but many of these predictions ignore physiological and behavioral plasticity that might buffer species from extinction. We evaluated the potential for physiological acclimatization and behavioral avoidance of poor climatic conditions to lower extinction risk under climate change in the global hotspot of salamander diversity, a region currently predicted to lose most of the salamander habitat due to warming. Our approach integrated experimental physiology and behavior into a mechanistic species distribution model to predict extinction risk based on an individual’s capacity to maintain energy balance with and without plasticity. We assessed the sensitivity of extinction risk to body size, behavioral strategies, limitations on energy intake, and physiological acclimatization of water loss and metabolic rate. The field and laboratory experiments indicated that salamanders readily acclimatize water loss rates and metabolic rates in ways that could maintain positive energy balance. Projections with plasticity reduced extinction risk by 72% under climate warming, especially in the core of their range. Further analyses revealed that juveniles might experience the greatest physiological stress under climate warming, but we identified specific physiological adaptations or plastic responses that could minimize the lethal physiological stress imposed on juveniles. We conclude that incorporating plasticity fundamentally alters ecological predictions under climate change by reducing extinction risk in the hotspot of salamander diversity

Giant crystal-electric-field effect and complex magnetic behavior in single-crystalline CeRh3Si2

Single-crystalline CeRh3Si2 was investigated by means of x-ray diffraction, magnetic susceptibility, magnetization, electrical resistivity, and specific heat measurements carried out in wide temperature and magnetic field ranges. Moreover, the electronic structure of the compound was studied at room temperature by cerium core-level x-ray photoemission spectroscopy (XPS). The physical properties were analyzed in terms of crystalline electric field and compared with results of ab-initio band structure calculations performed within the density functional theory approach. The compound was found to crystallize in the orthorhombic unit cell of the ErRh3Si2 type (space group Imma -- No.74, Pearson symbol: oI24) with the lattice parameters: a = 7.1330(14) A, b = 9.7340(19) A, and c = 5.6040(11) A. Analysis of the magnetic and XPS data revealed the presence of well localized magnetic moments of trivalent cerium ions. All physical properties were found to be highly anisotropic over the whole temperature range studied, and influenced by exceptionally strong crystalline electric field with the overall splitting of the 4f1 ground multiplet exceeding 5700 K. Antiferromagnetic order of the cerium magnetic moments at TN = 4.70(1)K and their subsequent spin rearrangement at Tt = 4.48(1) K manifest themselves as distinct anomalies in the temperature characteristics of all investigated physical properties and exhibit complex evolution in an external magnetic field. A tentative magnetic B-T phase diagram, constructed for B parallel to the b-axis being the easy magnetization direction, shows very complex magnetic behavior of CeRh3Si2, similar to that recently reported for an isostructural compound CeIr3Si2. The electronic band structure calculations corroborated the antiferromagnetic ordering of the cerium magnetic moments and well reproduced the experimental XPS valence band spectrum.Comment: 32 pages, 12 figures, to appear in Physical Review

Potential of the TROPOspheric Monitoring Instrument (TROPOMI) onboard the Sentinel-5 Precursor for the monitoring of terrestrial chlorophyll fluorescence

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

Processing Succinct Matrices and Vectors

We study the complexity of algorithmic problems for matrices that are represented by multi-terminal decision diagrams (MTDD). These are a variant of ordered decision diagrams, where the terminal nodes are labeled with arbitrary elements of a semiring (instead of 0 and 1). A simple example shows that the product of two MTDD-represented matrices cannot be represented by an MTDD of polynomial size. To overcome this deficiency, we extended MTDDs to MTDD_+ by allowing componentwise symbolic addition of variables (of the same dimension) in rules. It is shown that accessing an entry, equality checking, matrix multiplication, and other basic matrix operations can be solved in polynomial time for MTDD_+-represented matrices. On the other hand, testing whether the determinant of a MTDD-represented matrix vanishes PSPACE$-complete, and the same problem is NP-complete for MTDD_+-represented diagonal matrices. Computing a specific entry in a product of MTDD-represented matrices is #P-complete.Comment: An extended abstract of this paper will appear in the Proceedings of CSR 201

Infrared behavior of the gluon propagator in lattice Landau gauge: the three-dimensional case

We evaluate numerically the three-momentum-space gluon propagator in the lattice Landau gauge, for three-dimensional pure-SU(2) lattice gauge theory with periodic boundary conditions. Simulations are done for nine different values of the coupling $\beta$, from $\beta = 0$ (strong coupling) to $\beta = 6.0$ (in the scaling region), and for lattice sizes up to $V = 64^3$. In the limit of large lattice volume we observe, in all cases, a gluon propagator decreasing for momenta smaller than a constant value $p_{dec}$. From our data we estimate $p_{dec} \approx 350$ MeV. The result of a gluon propagator decreasing in the infrared limit has a straightforward interpretation as resulting from the proximity of the so-called first Gribov horizon in the infrared directions.Comment: 14 pages, BI-TP 99/03 preprint, correction in the Acknowledgments section. To appear in Phys.Rev.

Florix, an index to assess plant species in floodplains for nature conservation – Developed and tested along the river Danube

Natural floodplains are ecosystems with a diverse mosaic of habitats and site conditions, but also highly threatened due to anthropogenic pressures. Plant species occur in all habitat types and can indicate their value for nature conservation. To improve sustainable management of rivers and floodplains, several indices such as the River Ecosystem Service Index (RESI) have been developed. However, there are so far no assessment schemes for the entire range of floodplain plants. The common assessment approaches like biological integrity, achievement rates or threatened species (Red list), applying to other species groups or other ecosystems, are not appropriate in floodplains. Legal obligations and the need to restore floodplains clearly call for an index assessing the ecological value in a reference area which can be combined with a 5-scale assessment in accordance to established assessments like RESI or the Water Framework Directive. Five typical characteristics describing vascular plants’ adaptation to floodplain habitats were identified. These can be derived from published data sets available for all species in Germany. We checked these indicators for multicollinearity and selected three of them: species number, hydrodynamic indicators, nature conservation indicators. Species number highly correlate with habitat indicators and geographic occurrence. For the selected three indicators we determined thresholds to group habitats and their indicator rate to five classes (very low to very high value for nature conservation). These thresholds are valid for the river Danube and for the habitat types scrutinized in this study. The Florix approach was sensitive in data sets testing active against former floodplains and protected against unprotected areas: For the entire reference region ‘Danube floodplain’, Florix values were higher in the active floodplain and in the protected areas. Only the habitat type ‘water bodies’ showed better scores for habitats in the former floodplain, for ‘softwood forests’ the status of being part of a protected area had no effect. Florix results were validated in two case studies differing in land use intensity. The region with dominant agricultural use showed significantly lower values than that with a higher portion of forests and grasslands. Florix can be used for a floristic conservation status assessment at single habitat level or for the entity of a study region in comparison to a reference region. It allows to identify main pressures and to complement a habitat-type based evaluation. To achieve higher comparability, we should strive for a generalized monitoring in Europe like it is common in aquatic ecosystem monitoring

Daily torpor: When heart and brain go cold - Nonlinear cardiac dynamics in the seasonal heterothermic Djungarian hamster

Djungarian hamsters (Phodopus sungorus) acclimated to short photoperiod display episodes of spontaneous daily torpor with metabolic rate depressed by ∼70%, body temperature (

Exploring the conformational dynamics of alanine dipeptide in solution subjected to an external electric field: A nonequilibrium molecular dynamics simulation

In this paper, we investigate the conformational dynamics of alanine dipeptide under an external electric field by nonequilibrium molecular dynamics simulation. We consider the case of a constant and of an oscillatory field. In this context we propose a procedure to implement the temperature control, which removes the irrelevant thermal effects of the field. For the constant field different time-scales are identified in the conformational, dipole moment, and orientational dynamics. Moreover, we prove that the solvent structure only marginally changes when the external field is switched on. In the case of oscillatory field, the conformational changes are shown to be as strong as in the previous case, and non-trivial nonequilibrium circular paths in the conformation space are revealed by calculating the integrated net probability fluxes.Comment: 23 pages, 12 figure