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Holger Grtner 《Geomorphology》2007,86(3-4):243-251
Exposed roots have been used in Dendrogeomorphology since the 1960s to determine erosion rates. This was done by using the root axis as the relative position of the former soil layer and then relating this measure to the age of the root in order to quantify the amount of soil erosion over time. Recently, wood anatomical research revealed the possibility of determining the first year of exposure of roots due to specific anatomical changes within the respective annual ring. As a consequence, using exposed roots that are still in contact to the soil surface, it is possible to reconstruct the size and position of the root at the time of exposure. Consequently, a new equation is presented to calculate the thickness of the eroded soil layer allowing a detailed reconstruction of erosion rates. The technique also helps to determine if the root was exposed by erosional processes or just by its ongoing secondary growth without any erosion involved. 相似文献
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Holger Klein 《Ocean Dynamics》1987,40(3):87-102
Summary During the NOAMP Experiment (September '83 to May '86), 20 benthic storms with velocities of up to 27 cm/s and a duration of between 3 and 25 days, have been observed in a region centered at 47° 20 N and 20° W. The calculation of streamfunction maps shows clearly, that all storms between September '83 and September '84 occur in connection with deep reaching synoptic vortices. These events are important mechanisms for the dispersion of tracers, which are released at the seabed. They enable the particles to pass the interface between the well-mixed bottom boundary layer and the stratified interior of the deep sea. The eddies, with lifetimes of up to several months, trap the particles and facilitate horizontal and vertical transports within the eddy. Each vortex, by means of its shear, deforms a parcel of contaminated water to thin sheets, respectively to thin filaments with regard to two dimensions. This makes small-scale mixing processes work effectively.
Tiefseestürme, Wirbel und Teilchenausbreitung in der Tiefsee des Westeuropäischen Beckens
Zusammenfassung Während des NOAMP-Experiments wurden in einem Gebietbei 47° 20 N und 20° W 20 Tiefseestürme mit Geschwindigkeiten bis zu 27 cm/s und einer Dauer zwischen 3 und 25 Tagen gemessen. Stromfunktionskarten zeigen, daß, zumindest im Zeitraum von September '83 bis September '84, die Stürme stets im Zusammenhang mit tiefreichenden synoptischen Wirbeln auftreten. Diese Ereignisse sind von herausragender Bedeutung für die Ausbreitung am Tiefseeboden eingebrachter Stoffe. Sie ermöglichen den Austausch von Wasserkörpern durch die Sprungschicht zwischen der stark durchmischten Bodengrenzschicht und dem geschichteten Inneren der Tiefsee. Die Wirbel, mit Lebenszeiten bis zu mehreren Monaten, können Wasserkörper mit Eigenschaften, die ihn von der umgebenden Wassermasse unterscheiden, einfangen und transportieren sie vertikal und horizontal innerhalb des Wirbels. Jeder Wirbel deformiert solche Wasserkörper zu dünnen Scheiben, bzw. zu dünnen Filamenten im Zweidimensionalen, und schafft somit die notwendige Voraussetzung für das Wirken kleinskaliger Vermischungsprozesse.
Tempêtes de grands fonds, tourbillons, dispersion de particules dans les eaux profondes du Bassin de l'Europe de l'Ouest
Résumé Durant l'expérience NOAMP (septembre 1983 – Mai 1986), vingt tempêtes de grands fonds avec des vitesses supérieures à 27 cm/s et des durées comprises entre 3 et 25 jours, ont été observées dans un secteur centré sur le point 47° 20 nord et 20° ouest. Le calcul des cartes de courant montre clairement que les tempêtes sous-marines observées entre septembre 1983 et semtembre 1984 sont reliées à des tourbillons synoptiques atteignant de grandes profondeurs. Ces évènements sont des mécanismes importants pour la dispersion d'éléments — traces libérés sur le fond de l'océan. Ils permettent aux particules de franchir l'interface entre la couche limite de fond, homogène, et la partie stratifiée de la mer profonde. Les tourbillons qui ont des durées de vie de plusieurs mois, piègent les particules et facilitent leurs transports horizontaux et verticaux au sein même du tourbillon. Chaque tourbillon du fait du cisaillement, transforme un volume d'eau contaminée en minces couches, ou plutôt en minces filets d'eau, si l'on se place dans les deux dimensions. Cela génère en réalité un processus de mélange à petite échelle.相似文献
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Günter Leydecker Timo Schmitt Holger Busche Thomas Schaefer 《Soil Dynamics and Earthquake Engineering》2008,28(9):754-762
Within the scope of the licensing procedure for 12 interim storage facilities for spent nuclear fuel at nuclear power plants (NPP) and one for the dismantling of a NPP in Germany, site-specific expert reports were carried out to determine seismo-engineering design parameters. Our work was based on the German nuclear safety standard KTA 2201 part 1 “Design of Nuclear Power Plants against Seismic Events” which requires the derivation of the design earthquake in terms of (macroseismic) intensity. The intensity of the particular design earthquake was evaluated by the deterministic method stipulated in KTA 2201 part 1. According to the current state-of-the-art of science and technology supplementary to the deterministic approach, probabilistic evaluations were done setting a probability of exceedance for the occurrence of the design earthquake of 10−5 year−1. Geological development and neotectonic conditions of the site surrounding areas were included in the evaluations. For 13 interim storage facility sites, soil-dependent design spectra and corresponding strong-motion duration values were determined.For sites with low seismic hazard site-specific design spectra from the literature were used. In the case of sites with higher seismic hazard (design earthquakeVII 1/2 MSK) strong-motion registrations representative for the site were selected from world wide data and subsequently evaluated to derive site-specific design spectra. 相似文献
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YAN XiaoLu ZHENG XiangDong ZHOU XiuJi Holger VMEL SONG JianYang LI Wei MA YongHong ZHANG Yong 《中国科学:地球科学(英文版)》2015,58(4):589-603
We present validation studies of MLS V2.2 and V3.3 water vapor(WV) and ozone profiles over the Tibetan Plateau(Naqu and Lhasa) and its adjacent region(Tengchong) respectively by using the balloon-borne Cryogenic Frost point Hygrometer and Electrochemical Concentration Cell ozonesonde. Coincident in situ measurements were selected to compare the MLS V2.2 and V3.3 WV and ozone profiles for understanding the applicability of the two version MLS products over the region. MLS V2.2 and V3.3 WV profiles respectively show their differences within ?2.2±15.7%(n=74) and 0.3±14.9%(n=75) in the stratosphere at and above 82.5 h Pa. Accordingly, at 100 h Pa, the altitude approaching the tropopuase height, differences are within 9.8± 46.0%(n=18) and 23.0±45.8%(n=17), and they are within 21.5±90.6%(n=104) and 6.0±83.4%(n=99) in upper troposphere. The differences of MLS ozone are within ?11.7±16.3%(n=135, V2.2) and 15.6±24.2%(n=305, V3.3) at and above 82.5 h Pa. At 100 h Pa, they are within ?3.5±54.4%(n=27) and ?8.7±41.6%(n=38), and within 18.0±79.1%(n=47) and 34.2±76.6%(n=160) in the upper troposphere. The relative difference of MLS WV and ozone profile has significant oscillation and scatter at upper troposphere and lower stratosphere partly due to the stronger gradients of WV and ozone concentrations here as well the linear interpolation of sonde data for the intercomparison. At and below 70 h Pa, the relative differences of MLS ozone are significantly larger over Lhasa during the Tibetan Plateau "ozone valley" season, which is also the Asian Summer Monsoon period. The MLS ozone differences over the three sites are similar in their vertical distributions during that period. A simple linear correlation analysis between MLS and sonde profiles indicates that the sensitivity of MLS profile products is related to concentrations at each pressure level. The MLS V3.3 product sensitivity is slightly improved for WV at and above 82.5 h Pa, whereas it is not obvious for ozone. The possible factors contributing to the differences of the MLS profile products of WV and ozone are discussed. 相似文献