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    Drought Characteristics Derived Based on the Standardized Streamflow Index: A Large Sample Comparison for Parametric and Nonparametric Methods (2021)
    Details
    Publication Date: 2021-10-01
    Description: The streamflow drought hazard can be characterized in a variety of ways, including using different indices. Traditionally, percentile-based indices, such as Q95 (the flow exceeded 95% of time), have been used by the hydrological community. Recently, the use of anomaly indices such as the Standardized Streamflow Index (SSI), a probability index-based approach adopted from the climatological community, has increased in popularity. The SSI can be calculated based on various (non)parametric methods. Up to now, there is no consensus which method to use. This study aims to raise awareness how the inherent sensitivity of the SSI to the used method influences derived drought characteristics. We compared SSI time series computed with seven different probability distributions and two fitting methods as well as with different nonparametric methods for 369 rivers across Europe. Results showed that SSI time series and associated drought characteristics are indeed sensitive to the method of choice. A resampling experiment demonstrated the sensitivity of the parametric SSI to properties of both the low and high end of the sample. Such sensitivities might hinder a fair comparison of drought in space and time and highlight the need for a clear recommendation which method to use. We could recommend overall suitable methods, for example, from the parametric approaches, the Tweedie distribution has several advantageous properties such as a low rejection rate (2%) and a lower bound at zero. However, the most suitable method depends on the used evaluation criteria. Rather, we stress that shown approach-specific sensitivities and uncertainties should be carefully considered.
    Keywords: 551.48 ; drought ; parametric ; drought identification ; Standardized Streamflow Index ; sensitivity analyses ; nonparametric
    Language: English
    Type: map
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    CITATION GEO-LEO
  • 2
    Electronic Resource
    Electronic Resource
    Gruppenspezifische Analyse von Citratcyclusintermediaten in der modernen Flüssigkeits-Chromatographie im unteren Nanoval-Bereich (1972)
    Springer
    Fresenius' Zeitschrift für analytische Chemie 261 (1972), S. 354-358 
    Details
    ISSN: 1618-2650
    Keywords: Analyse von Carbonsäuren (Citratcyelus) ; durch Chromatographie ; Säule im nVal-Bereich
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Es wird über die Analyse von Citratcyclusintermediaten mit Hilfe der modernen Flüssigkeits-Chromatographie (LC) berichtet. Der photometrische Nachweis der kurzkettigen Carbonsäuren im Säuleneluat erfolgt mit Hilfe eines gruppenspezifischen Indicators (o-Nitro-Phenol). Bei gradientenfreier Elution beträgt der Rauschpegel der Basislinie des Chromatogramms max. 1 · 10−3 E und der Flächenwert für 10 nVal Essigsäure 25 E · sec. Bei wiederholten Probenaufgaben betragen die Abweichungen vom Flächenmittelwert max. ± 5% (VB 95%). Die Aufbereitung biologischer Proben erfolgt durch Extraktion mit Diäthyläther in einer einfachen säulen-chromatographischen Anlage, die gleichzeitig der Vortrennung sog. „kritischer Säurenpaare” dient. Die Anwendbarkeit der LC auf die Analyse von biologischem Material wird mit einem Chromatogramm von 10 μl Humanserum gezeigt.
    Notes: Abstract The analysis of TCA intermediates and related compounds with modern liquid chromatography (LC) is described. Short-chain carboxylic acids are detected by adding a compound specific indicator (o-nitro-phenol) to the eluent. Without gradient elution, the noise level of the chromatogram baseline does not exceed 1×10−3 O.D. and the peak area for 10 nanoequivalent acetic acid is 25 absorbance seconds. With repeated applications of sample to column, deviations of 5% of the medium peak area value are not exceeded (range of confidence 95%). Preparation of the biological samples is achieved by ether extraction with a simple column-chromatography apparatus, which at the same time, preseparates critical acids otherwise not completely separable by elution without gradient. The application of LC to the analysis of biological material is demonstrated by a chromatogram of 10 μl of human serum.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00786994
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