GIS approach to scale issues of perimeter-based shape indices for drainage basins     

ANDRÁS BÁRDOSSY  FRIDJOF SCHMIDT 《水文科学杂志》2013,58(6):931-942

Abstract

Shape indices have been in use for several decades to describe the characteristics and hydrological properties of drainage basins. Due to the fractal behaviour of the basin boundary, perimeter-based shape indices depend on the scale at which they are determined. Therefore, these indices cannot objectively compare drainage basins across a range of scales and basin sizes. This paper presents an objective GIS-based methodology for determining scale-dependent shape indices from gridded drainage basin representations. The scale effect is addressed by defining a representative scale at which the indices should be determined, based on a threshold symmetric difference between two grids representing the drainage basin at different resolutions.  相似文献   

THE RESPONSE OF PARTIALLY DEBRIS‐COVERED VALLEY GLACIERS TO CLIMATE CHANGE: THE EXAMPLE OF THE PASTERZE GLACIER (AUSTRIA) IN THE PERIOD 1964 TO 2006     

ANDREAS KELLERER‐PIRKLBAUER  GERHARD KARL LIEB  MICHAEL AVIAN  JOSEF GSPURNING 《Geografiska Annaler: Series A, Physical Geography》2008,90(4):269-285

Long‐term observations of partly debris‐covered glaciers have allowed us to assess the impact of supra‐glacial debris on volumetric changes. In this paper, the behaviour of the partially debris‐covered, 3.6 km² tongue of Pasterze Glacier (47°05′N, 12°44′E) was studied in the context of ongoing climate changes. The right part of the glacier tongue is covered by a continuous supra‐glacial debris mantle with variable thicknesses (a few centimetres to about 1 m). For the period 1964–2000 three digital elevation models (1964, 1981, 2000) and related debris‐cover distributions were analysed. These datasets were compared with long‐term series of glaciological field data (displacement, elevation change, glacier terminus behaviour) from the 1960s to 2006. Differences between the debriscovered and the clean ice parts were emphasised. Results show that volumetric losses increased by 2.3 times between the periods 1964–1981 and 1981–2000 with significant regional variations at the glacier tongue. Such variations are controlled by the glacier emergence velocity pattern, existence and thickness of supra‐glacial debris, direct solar radiation, counter‐radiation from the valley sides and their changes over time. The downward‐increasing debris thickness is counteracting to a compensational stage against the common decrease of ablation with elevation. A continuous debris cover not less than 15 cm in thickness reduces ablation rates by 30–35%. No relationship exists between glacier retreat rates and summer air temperatures. Substantial and varying differences of the two different terminus parts occurred. Our findings clearly underline the importance of supra‐glacial debris on mass balance and glacier tongue morphology.  相似文献   

Depolarization ratio profiling at several wavelengths in pure Saharan dust during SAMUM 2006   总被引：1，自引：0，他引：1  

By VOLKER FREUDENTHALER  MICHAEL ESSELBORN  MATTHIAS WIEGNER  BIRGIT HEESE  MATTHIAS TESCHE  ALBERT ANSMANN  DETLEF MÜLLER  DIETRICH ALTHAUSEN  MARTIN WIRTH  REAS FIX  GERHARD EHRET  PETER KNIPPERTZ  CARLOS TOLEDANO  JOSEF GASTEIGER  MARKUS GARHAMMER  MEINHARD SEEFELDNER 《Tellus. Series B, Chemical and physical meteorology》2009,61(1):165-179

Vertical profiles of the linear particle depolarization ratio of pure dust clouds were measured during the Saharan Mineral Dust Experiment (SAMUM) at Ouarzazate, Morocco (30.9°N, –6.9°E), close to source regions in May–June 2006, with four lidar systems at four wavelengths (355, 532, 710 and 1064 nm). The intercomparison of the lidar systems is accompanied by a discussion of the different calibration methods, including a new, advanced method, and a detailed error analysis. Over the whole SAMUM periode pure dust layers show a mean linear particle depolarization ratio at 532 nm of 0.31, in the range between 0.27 and 0.35, with a mean Ångström exponent (AE, 440–870 nm) of 0.18 (range 0.04–0.34) and still high mean linear particle depolarization ratio between 0.21 and 0.25 during periods with aerosol optical thickness less than 0.1, with a mean AE of 0.76 (range 0.65–1.00), which represents a negative correlation of the linear particle depolarization ratio with the AE. A slight decrease of the linear particle depolarization ratio with wavelength was found between 532 and 1064 nm from 0.31 ± 0.03 to 0.27 ± 0.04.  相似文献   

A recent build-up of atmospheric CO₂ over Europe. Part 1: observed signals and possible explanations     

By MICHEL RAMONET  PHILIPPE CIAIS  TUULA AALTO  CÉLINE AULAGNIER  FRÉDÉRIC CHEVALLIER  DOMENICO CIPRIANO  THOMAS J. CONWAY  LASZLO HASZPRA  VICTOR KAZAN  FRANK MEINHARDT  JEAN-DANIEL PARIS  MARTINA SCHMIDT  PETER SIMMONDS  IRÈNE XUEREF-RÉMY  JAROSLAW N. NECKI 《Tellus. Series B, Chemical and physical meteorology》2010,62(1):1-13

We analysed interannual and decadal changes in the atmospheric CO₂ concentration gradient (ΔCO₂) between Europe and the Atlantic Ocean over the period 1995–2007. Fourteen measurement stations are used, with Mace-Head being used to define background conditions. The variability of ΔCO₂ reflects fossil fuel emissions and natural sinks activity over Europe, as well as atmospheric transport variability. The mean ΔCO₂ increased by 1–2 ppm at Eastern European stations (∼30% growth), between 1990–1995 and 2000–2005. This built up of CO₂ over the continent is predominantly a winter signal. If the observed increase of ΔCO₂ is explained by changes in ecosystem fluxes, a loss of about 0.46 Pg C per year would be required during 2000–2005. Even if severe droughts have impacted Western Europe in 2003 and 2005, a sustained CO₂ loss of that magnitude is unlikely to be true. We sought alternative explanations for the observed CO₂ build-up into transport changes and into regional redistribution of fossil fuel CO₂ emissions. Boundary layer heights becoming shallower can only explain 32% of the variance of the signal. Regional changes of emissions may explain up to 27% of the build-up. More insights are given in the Aulagnier et al. companion paper.  相似文献   

Chrysophyte resting stages: a tool for reconstructing winter/spring climate from Alpine lake sediments   总被引：4，自引：0，他引：4  

CHRISTIAN KAMENIK  ROLAND SCHMIDT 《Boreas: An International Journal of Quaternary Research》2005,34(4):477-489

Chrysophyte algae produce siliceous resting stages (stomatocysts) that are indicators of past environmental conditions. The objective of this study was to assess their strength for climate reconstructions. Stomatocysts were collected using sediment traps exposed in 45 mountain lakes (1502-2309 m a.s.l., Austrian Alps). Bi-hourly water-temperature measurements were used to determine dates of freezing and break-up, spring and autumn mixing. Canonical correspondence analyses revealed that the stomatocyst assemblages were related to the dates of ice break-up and spring mixing. The two dates are controlled by winter/spring air temperature. We developed a weighted averaging-partial least squares (WA-PLS) stomatocyst/date-of-spring-mixing regression and calibration model (R² _boot=0.85), and reconstructed 'dates of spring mixing' for Jezero v Ledvici (1824 m a.s.l., Slovenian Alps) from AD 1842 to 1996. Sample-specific standard errors of prediction corresponded to 0.6°C - 1.0°C. Despite dating uncertainties and poor fits of fossil assemblages with the training set, reconstructed 'dates of spring mixing' were significantly correlated with the mean March-April air temperature, which is known to drive break-up dates. Furthermore, the record was in agreement with glacier advances during the Little Ice Age.  相似文献   

Island-arc Ankaramites: Primitive Melts from Fluxed Refractory Lherzolitic Mantle   总被引：7，自引：1，他引：7  

GREEN  D. H.; SCHMIDT  M. W.; HIBBERSON  W. O. 《Journal of Petrology》2004,45(2):391-403

The distinctive island-arc ankaramites exemplified by the activeVanuatu arc may be produced by melting of refractory lherzoliteunder conditions in which melting is fluxed by H₂O + CO₂. Parentalpicritic ankaramite magmas with maximum CaO/Al₂O₃ to  相似文献   

SEDIMENT BUDGETS AND RATES OF SEDIMENT TRANSFER ACROSS COLD ENVIRONMENTS IN EUROPE: INTRODUCTION AND BACKGROUND TO THE EUROPEAN SCIENCE FOUNDATION NETWORK 'SEDIMENTARY SOURCE-TO-SINK FLUXES IN COLD ENVIRONMENTS'(SEDIFLUX)     

JEFF WARBURTON  ACHIM A. BEYLICH  SAMUEL ETIENNE  BERND ETZELMÜLLER  VYACHESLAV V. GORDEEV  JUKKA KÄYHKÖ  HUGUES LANTUIT  REW J. RUSSELL  ÞORSTEINN SÆMUNDSSON  KARL-HEINZ SCHMIDT  FIONA S. TWEED 《Geografiska Annaler: Series A, Physical Geography》2007,89(1):1-3

  相似文献   

HYDROLOGY AND GEOMORPHIC EFFECTS OF A HIGH-MAGNITUDE FLOOD IN AN ALPINE RIVER     

DAVID MORCHE  KARL-HEINZ SCHMIDT  TOBIAS HECKMANN  FLORIAN HAAS 《Geografiska Annaler: Series A, Physical Geography》2007,89(1):5-19

The catchment of the River Partnach, a torrent situated in a glacial valley in the Northern Calcareous Alps of Bavaria/Germany, was affected by a high‐magnitude flood on 22/23 August 2005 with a peak discharge of more than 16 m³s^‐1 at the spring and about 50 m³s^‐1 at the catchment outlet. This flood was caused by a long period of intense rainfall with a maximum intensity of 230 mm per day. During this event, a landslide dam, which previously held a small lake, failed. The flood wave originating from the dam breach transported a large volume of sediment (more than 50 000 m³) derived from bank erosion and the massive undercutting of a talus cone. This caused a fundamental transformation of the downstream channel system including the redistribution of large woody debris and channel switching. Using terrestrial survey and aerial photography, erosional and depositional consequences of the event were mapped, pre‐ and post‐event surfaces were compared and the sediment budget of the event calculated for ten consecutive channel reaches downstream of the former lake. According to the calculations more than 100 000 tonnes of sediment were eroded, 75% of which was redeposited within the channel and the proximal floodplain. A previous large flood which occurred a few weeks prior to the August 2005 event had a significant effect on controlling the impact of this event.  相似文献   

STRATIGRAPHY AND GEOLOGIC HISTORY OF THE SABKHA, ABU DHABI, PERSIAN GULF   总被引：1，自引：0，他引：1  

G. EVANS  V. SCHMIDT  P. BUSH  H. NELSON 《Sedimentology》1969,12(1-2):145-159

  相似文献   

Sediment trend models fail to reproduce small-scale sediment transport patterns on an intertidal beach   总被引：2，自引：0，他引：2  

GERHARD MASSELINK  DANIEL BUSCOMBE  MARTIN AUSTIN†  TIM O'HARE†  PAUL RUSSELL† 《Sedimentology》2008,55(3):667-687

A rigorous test is presented of the application of sediment trend models to an intertidal beach environment characterized by bar morphology. Sediment samples were collected during low tide from a regular grid and their sediment fall velocity distributions, obtained using a settling tube, were analysed using moment analysis. The net sediment transport direction determined from beach surveys, hydrodynamic measurements, wave ripple observations and sediment transport modelling was compared with predictions by sediment trend models based on the spatial distribution of sediment parameters. It was found that the sediment transport pathways and patterns of sedimentation predicted using sediment trend models were at odds with field observations, and varied significantly depending on whether surface or sub‐surface sediment samples were used. The sediment trend models are thought to fail because, in energetic and morphologically variable beach environments, spatial patterns in sediment characteristics are mainly attributed to the presence of different hydrodynamic regions and associated morphology, rather than sediment pathways. The use of sediment trend models cannot replace the collection of morphological, hydrodynamic and sediment transport data in the field to define relationships between flows, forms and sedimentation patterns on a dynamic intertidal beach.  相似文献