Many recent studies have sought to characterize variations of the annual maximum flood discharge series over time and across space in Europe, including some that have elucidated different process ...controls on different statistical properties of these series. To further support these studies, we conduct a pan-European assessment of process controls on key properties of this series, including the mean annual flood (MAF) and coefficients of variation (CV) and skewness (CS) of flood discharges. These annual maximum flood discharge series consist of instantaneous peaks and daily means observed in 2370 catchments in Europe without strong human modifications covering the period 1960-2010. We explore how the estimated moments MAF, CV and CS vary due to catchment size, climate and other controls across Europe, where their averages are 0.17 m.sup.3 s.sup.-1 km.sup.-2, 0.52 and 1.28, respectively.
The recent advances in remote sensing provide opportunities for estimating the parameters of conceptual hydrologic models more reliably. However, the question of whether and to what extent the use of ...satellite data in model calibration may assist in transferring model parameters to ungauged catchments has not been fully resolved. The aim of this study is to evaluate the efficiency of different methods for transferring model parameters obtained by multiple-objective calibrations to ungauged sites and to assess the model performance in terms of runoff, soil moisture, and snow cover predictions relative to existing regionalization approaches. The model parameters are calibrated to daily runoff, satellite soil moisture (Advanced Scatterometer – ASCAT), and snow cover (Moderate Resolution Imaging Spectroradiometer – MODIS) data. The assessment is based on 213 catchments situated in different physiographic and climate zones of Austria. For the transfer of model parameters, eight methods (global and local variants of arithmetic mean, regression, spatial proximity, and similarity) are examined in two periods, i.e., the period in which the model is calibrated (2000–2010) and an independent validation period (2010–2014). The predictive accuracy is evaluated by the leave-one-out cross-validation. The results show that the method by which the model is calibrated in the gauged catchment has a larger impact on runoff prediction accuracy in the ungauged catchments than the choice of the parameter transfer method. The best transfer methods are global and local similarity and the kriging approach. The performance of the transfer methods differs between lowland and alpine catchments. While the soil moisture and snow cover prediction efficiencies are higher in lowland catchments, the runoff prediction efficiency is higher in alpine catchments. A comparison of the model transfer methods, based on parameters calibrated to runoff, snow cover, and soil moisture with those based on parameters calibrated to runoff, only indicates that the former outperforms the latter in terms of simulating soil moisture and snow cover. The performance of simulating runoff is similar, and the accuracy depends mainly on the weight given to the runoff objective in the multiple-objective calibrations.
A spatially distributed flash flood forecasting model Blöschl, Günter; Reszler, Christian; Komma, Jürgen
Environmental modelling & software : with environment data news,
04/2008, Letnik:
23, Številka:
4
Journal Article
Recenzirano
This paper presents a distributed model that is in operational use for forecasting flash floods in northern Austria. The main challenge in developing the model was parameter identification which was ...addressed by a modelling strategy that involved a model structure defined at the model element scale and multi-source model identification. The model represents runoff generation on a grid basis and lumped routing in the river reaches. Ensemble Kalman Filtering is used to update the model states (grid soil moisture) based on observed runoff. The forecast errors as a function of forecast lead time are evaluated for a number of major events in the 622
km
2 Kamp catchment and range from 10% to 30% for 4–24
h lead times, respectively.
Karst aquifers are an important water resource, but are particularly
vulnerable to pollution due to the typically short residence times. As the
rainwater runs off on the surface it may collect ...contamination from faeces
and other sources, before infiltrating the surface. It is therefore important to understand
the spatial distribution of the frequency of surface runoff in karst areas.
This paper proposes a new field-mapping method for the ability of the
landscape to produce and convey surface runoff. The mapping method is based
on (i) prior spatial information (e.g. geological map, terrain model), (ii) a
visual assessment from a distance at the landscape scale (e.g. traces of
surface runoff) and (iii) local data collection in the field (e.g. soil
moisture, grain size distribution). The focus on variables that can be
assessed from a distance in the landscape makes the method suitable for
mapping larger areas than traditional field mapping. The mapping method is
developed and tested for the 60 km2 Hochschwab area in Austria. The
field mapping is used to specify a surface runoff propensity index which is
tested against the spatial distribution of observed sink holes in the area.
The mapping indicates that, in the study region, runoff occurs much more
frequently in the poorly karstified dolomitic areas than in the limestone
areas that are highly karstified. On dolomites, low permeable soils or debris
prevail, often resulting in a permanent surface drainage network. On
karstified limestone, sometimes overlaid by debris, surface runoff only
occurs through infiltration excess at high rainfall intensities. Overall the
analyses suggest that the mapping method is suitable for efficiently and
reliably identifying spatial patterns of the ability of the landscape to
produce and convey surface runoff in karst areas.
Flood hazard mapping is currently in a transitional phase involving the use of data and methods that were traditionally in the domain of local studies in a regional or nationwide context. Challenges ...include the representation of local information such as hydrological particularities and small hydraulic structures, as well as computational and labour costs. This paper proposes a methodology of flood hazard mapping that merges the best of the two worlds (local and regional studies) based on experiences in Austria. The analysis steps include (a) quality control and correction of river network and catchment boundary data; (b) estimation of flood discharge peaks and volumes on the entire river network; (c) creation of a digital elevation model (DEM) that is consistent with all relevant flood information, including riverbed geometry; and (d) simulation of inundation patterns and velocities associated with a consistent flood return period across the entire river network. In each step, automatic methods are combined with manual interventions in order to maximise the efficiency and at the same time ensure estimation accuracy similar to that of local studies. The accuracy of the estimates is evaluated in each step. The study uses flood discharge records from 781 stations to estimate flood hazard patterns of a given return period at a resolution of 2 m over a total stream length of 38 000 km. It is argued that a combined local–regional methodology will advance flood mapping, making it even more useful in nationwide or global contexts.
The Ncd microtubule motor protein is required for meiotic and early mitotic chromosome distribution in Drosophila. Null mutant females expressing the Ncd motor fused to the Aequorea victoria green ...fluorescent protein (GFP), regulated by the wild-type ncd promoter, are rescued for chromosome segregation and embryo viability. Analysis of mitosis in live embryos shows cell cycle-dependent localization of Ncd-GFP to centrosomes and spindles. The distribution of Ncd-GFP in spindles during metaphase differs strikingly from that of tubulin: the tubulin staining is excluded by the chromosomes at the metaphase plate; in contrast, Ncd-GFP forms filaments along the spindle microtubules that extend across the chromosomes. The existence of Ncd-GFP fibers that cross the metaphase plate suggests that Ncd interacts functionally with chromosomes in metaphase. Differences are no longer observed in anaphase when the chromosomes have moved off the metaphase plate. A mutant form of Ncd fused to GFP also localizes to spindles in live embryos. Mutant embryos show frequent centrosome and spindle abnormalities, including free centrosomes that dissociate from interphase nuclei, precociously split centrosomes, and spindles with microtubule spurs or bridges to nearby spindles. The precociously split and free centrosomes indicate that the Ncd motor acts in cleavage stage embryos to maintain centrosome integrity and attachment to nuclei. The frequent spindle spurs of mutant embryos are associated with mis-segregating chromosomes that partially detach from the spindle in metaphase, but can be recaptured in early anaphase. This implies that the Ncd motor functions to prevent chromosome loss by maintaining chromosome attachment to the spindle in metaphase, consistent with the Ncd-GFP fibers that across the metaphase plate.
Nonclaret disjunctional (ncd) is a kinesin-related microtubule motor protein required for meiotic and early mitotic chromosome distribution in Drosophila. ncd translocates on microtubules with the ...opposite polarity to kinesin, toward microtubule minus ends, and is associated with spindles in chromosome/spindle preparations. Here we report a new mutant of ncd caused by partial deletion of the predicted coiled-coil central stalk. The mutant protein exhibits a velocity of translocation and ability to generate torque in motility assays comparable to near full-length ncd, but only partially rescues a null mutant for chromosome mis-segregation. Antibody staining experiments show that the partial loss-of-function and null mutants cause centrosomal and spindle pole defects, including centrosome splitting and loss of centrosomes from spindle poles, and localize ncd to centrosomes as well as spindles of wild-type embryos. Association of ncd with spindles and centrosomes is microtubule- and cell cycle-dependent: inhibition of microtubule assembly with colchicine abolishes ncd staining and centrosomal staining is observed in prometaphase, metaphase and anaphase, but diminishes in late anaphase/telophase. The cell cycle dependence of centrosomal staining and the defects of mutants provide clear evidence for activity of the ncd motor protein near or at the spindle poles in mitosis. The ncd motor may interact with centrosomal microtubules and spindle fibers to attach centrosomes to spindle poles, and mediate poleward translocation (flux) of kinetochore fibers, a process that may underlie poleward movement of chromosomes in mitosis. Together with previous work, our findings indicate that ncd is important in maintaining spindle poles in mitosis as well as in meiosis.
The meiosis II spindle of Drosophila oocytes is distinctive in structure, consisting of two tandem spindles with anastral distal poles and an aster-associated spindle pole body between the central ...poles. Assembly of the anastral:astral meiosis II spindle occurs by reorganization of the meiosis I spindle, without breakdown of the meiosis I spindle. The unusual disk- or ring-shaped central spindle pole body forms de novo in the center of the elongated meiosis I spindle, followed by formation of the central spindle poles. gamma-Tubulin transiently localizes to the central spindle pole body, implying that the body acts as a microtubule nucleating center for assembly of the central poles. Localization of gamma-tubulin to the meiosis II spindle is dependent on the microtubule motor protein, Nonclaret disjunctional (Ncd). Absence of Ncd results in loss of gamma-tubulin localization to the spindle and destabilization of microtubules in the central region of the spindle. Assembly of the anastral:astral meiosis II spindle probably involves rapid reassortment of microtubule plus and minus ends in the center of the meiosis I spindle - this can be accounted for by a model that also accounts for the loss of gamma-tubulin localization to the spindle and destabilization of microtubules in the absence of Ncd.
Spindle assembly and elongation involve poleward and away‐from‐the‐pole forces produced by microtubule dynamics and spindle‐associated motors. Here, we show that a bidirectional Drosophila Kinesin‐14 ...motor that moves either to the microtubule plus or minus end in vitro unexpectedly causes only minor spindle defects in vivo. However, spindles of mutant embryos are longer than wild type, consistent with increased plus‐end motor activity. Strikingly, suppressing spindle dynamics by depriving embryos of oxygen causes the bidirectional motor to show increased accumulation at distal or plus ends of astral microtubules relative to wild type, an effect not observed for a mutant motor defective in motility. Increased motor accumulation at microtubule plus ends may be due to increased slow plus‐end movement of the bidirectional motor under hypoxia, caused by perturbation of microtubule dynamics or inactivation of the only other known Drosophila minus‐end spindle motor, cytoplasmic dynein. Negative‐stain electron microscopy images are consistent with highly cooperative motor binding to microtubules, and gliding assays show dependence on motor density for motility. Mutant effects of the bidirectional motor on spindle function may be suppressed under normal conditions by motor: motor interactions and minus‐end movement induced by spindle dynamics. These forces may also bias wild‐type motor movement toward microtubule minus ends in live cells. Our findings link motor : motor interactions to function in vivo by showing that motor density, together with cellular dynamics, may influence motor function in live cells.
Haploidy and androgenesis in Drosophila Komma, D.J. (Duke University Medical Center, Durham, NC.); Endow, S.A
Proceedings of the National Academy of Sciences - PNAS,
12/1995, Letnik:
92, Številka:
25
Journal Article
Recenzirano
Odprti dostop
Androgenesis, development from paternal but not maternal chromosomes, can be induced to occur in some organisms, including vertebrates, but has only been reported to occur naturally in interspecific ...hybrids of the Sicilian stick insect. Androgenesis has not been described previously in Drosophila. We now report the recovery of androgenetic offspring from Drosophila melanogaster females mutant for a gene that affects an oocyte- and embryo-specific alpha-tubulin. The androgenetic exceptions are X,X diploid females that develop from haploid embryos and express paternal markers on all 4 chromosomes. The exceptional females arise by fusion of haploid cleavage nuclei or failure of newly replicated haploid chromosomes to segregate, rather than fusion of two inseminating sperm. The frequency of androgenetic offspring is greatly enhanced by a partial loss-of-function mutant of the NCD (nonclaret disjunctional) microtubule motor protein, suggesting that wild-type NCD functions in pronuclear fusion. Diploidization of haploid paternal chromosome complements results in complete genetic homozygosity, which could facilitate studies of gene variation and mutational load in populations
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