Long-term solar UV radiation reconstructed by Artificial Neural Networks (ANN)

International audienceArtificial Neural Networks (ANN) are efficient tools to derive solar UV radiation from measured meteorological parameters such as global radiation, aerosol optical depths and atmospheric column ozone. The ANN model has been tested with different combinations of data from the two sites Potsdam and Lindenberg, and used to reconstruct solar UV radiation at eight European sites by more than 100 years into the past. Annual totals of UV radiation derived from reconstructed daily UV values reflect interannual variations and long-term patterns that are compatible with variabilities and changes of measured input data, in particular global dimming by about 1980?1990, subsequent global brightening, volcanic eruption effects such as that of Mt. Pinatubo, and the long-term ozone decline since the 1970s. Patterns of annual erythemal UV radiation are very similar at sites located at latitudes close to each other, but different patterns occur between UV radiation at sites in different latitude regions

The trophic status of the fish fauna in Lago Camaleão, a macrophyte dominated floodplain lake in the middle Amazon

Food offer and consumption by the fish fauna were studied at medium and high waterlevels in a macrophyte dominated and strongly hypoxic floodplain lake of the middle Amazon. Detritus was shown to be the main food item, followed by terrestrial invertebrates and periphyton. Low aquatic macrophyte consumption is related to its low nutrient value in comparison with other abundant foods and its seasonal availability

Herbaceous plants of the Amazon floodplain near Manaus: Species diversity and adaptations to the flood pulse

In the floodplain of the Amazon river near Manaus, 388 herbaceous plant species, excepting epiphytes, were collected belonging to 64 families and 182 genera. 330 species are considered terrestrial, 34 aquatic, the others have an intermediate status. Most of the species occur in relatively small numbers. Only 17 species formed large monospecific stands. The largest number of species (273) was found during the dry phase in disturbed areas on the levees, as for instance in abandoned fields, because of a reduced impact of the flood and high light intensity. Low numbers were recorded during low water period from the floor of floodplain forest (25) because of insufficient light conditions and from low lying lake beds (26), which were dominated by a few highly adapted species. The following attributes were found to favour the occurrence of herbaceous plants in the Amazon floodplain: resistance of seeds and spores to flooding and dessication; short reproductive cycles; high reproduction rates; high primary production; tolerance of adult plants to flooding and drought; adaptations to waterlevel fluctuations (for example a floating way of life). Short life cycles and high reproduction rates allow the quick colonization of disturbed habitats and the substitution of population losses (r-strategy). This strategy is supported by the elevated nutrient status of the Amazon river floodplain in comparison with the floodplain of the Negro River, where herbaceous plants are scarce. The number of ruderal species and weeds including a rising number of neophytes is large. The great species diversity is related to great habitat diversity, fertility of sediments and water, predictability of the floodpulse and the reduction of interspecifìc competition due to the annual set back of the populations by the flooding and drought. The observations are in concordance with the predictions of the floodpulse concept

The effect of flooding on the exchange of the volatile C₂-compounds ethanol, acetaldehyde and acetic acid between leaves of Amazonian floodplain tree species and the atmosphere

The effect of root inundation on the leaf emissions of ethanol, acetaldehyde and acetic acid in relation to assimilation and transpiration was investigated with 2–3 years old tree seedlings of four Amazonian floodplain species by applying dynamic cuvette systems under greenhouse conditions. Emissions were monitored over a period of several days of inundation using a combination of Proton Transfer Reaction Mass Spectrometry (PTR-MS) and conventional techniques (HPLC, ion chromatography). Under non-flooded conditions, none of the species exhibited measurable emissions of any of the compounds, but rather low deposition of acetaldehyde and acetic acid was observed instead. Tree species specific variations in deposition velocities were largely due to variations in stomatal conductance. Flooding of the roots resulted in leaf emissions of ethanol and acetaldehyde by all species, while emissions of acetic acid were only observed from the species exhibiting the highest ethanol and acetaldehyde emission rates. All three compounds showed a similar diurnal emission profile, each displaying an emission burst in the morning, followed by a decline in the evening. This concurrent behavior supports the conclusion, that all three compounds emitted by the leaves are derived from ethanol produced in the roots by alcoholic fermentation, transported to the leaves with the transpiration stream and finally partly converted to acetaldehyde and acetic acid by enzymatic processes. Co-emissions and peaking in the early morning suggest that root ethanol, after transportation with the transpiration stream to the leaves and enzymatic oxidation to acetaldehyde and acetate, is the metabolic precursor for all compounds emitted, though we can not totally exclude other production pathways. Emission rates substantially varied among tree species, with maxima differing by up to two orders of magnitude (25–1700 nmol m−2 min−1 for ethanol and 5–500 nmol m−2 min−1 for acetaldehyde). Acetic acid emissions reached 12 nmol m−2 min−1. The observed differences in emission rates between the tree species are discussed with respect to their root adaptive strategies to tolerate long term flooding, providing an indirect line of evidence that the root ethanol production is a major factor determining the foliar emissions. Species which develop morphological root structures allowing for enhanced root aeration produced less ethanol and showed much lower emissions compared to species which lack gas transporting systems, and respond to flooding with substantially enhanced fermentation rates and a non-trivial loss of carbon to the atmosphere. The pronounced differences in the relative emissions of ethanol to acetaldehyde and acetic acid between the tree species indicate that not only the ethanol production in the roots but also the metabolic conversion in the leaf is an important factor determining the release of these compounds to the atmosphere

The Finite-Volume-Particle Method for Conservation Laws

In the Finite-Volume-Particle Method (FVPM), the weak formulation of a hyperbolic conservation law is discretized by restricting it to a discrete set of test functions. In contrast to the usual Finite-Volume approach, the test functions are not taken as characteristic functions of the control volumes in a spatial grid, but are chosen from a partition of unity with smooth and overlapping partition functions (the particles), which can even move along pre­scribed velocity fields. The information exchange between particles is based on standard numerical flux functions. Geometrical information, similar to the surface area of the cell faces in the Finite-Volume Method and the corresponding normal directions are given as integral quantities of the partition functions. After a brief derivation of the Finite-Volume-Particle Method, this work focuses on the role of the geometric coefficients in the scheme

A Lattice Study of Spectator Effects in Inclusive Decays of B-Mesons

We compute the matrix elements of the operators which contribute to spectator effects in inclusive decays of $B$-mesons. The results agree well with estimates based on the vacuum saturation (factorization) hypothesis. For the ratio of lifetimes of charged and neutral mesons we find $\tau(B^-)/\tau(B_d)=1.03\pm 0.02\pm 0.03$, where the first error represents the uncertainty in our evaluation of the matrix elements, and the second is an estimate of the uncertainty due to the fact that the Wilson coefficient functions have only been evaluated at tree-level in perturbation theory. This result is in agreement with the experimental measurement. We also discuss the implications of our results for the semileptonic branching ratio and the charm yield.Comment: 25 pages (figures are included). Revised version (some numerical integrals have been recomputed