Taking the pulse of hydrology education     

Thorsten Wagener  Markus Weiler  Brian McGlynn  Mike Gooseff  Tom Meixner  Lucy Marshall  Kevin McGuire  Mike McHale 《水文研究》2007,21(13):1789-1792

  相似文献   

Grain size and depositional environment as predictors of permeability in coastal marine sands     

Alicia M. Wilson  Markus Huettel  Stephen Klein 《Estuarine, Coastal and Shelf Science》2008

More than half of the surface sediments covering the continental shelves are sandy, which may permit substantial sub-seafloor pore water advection. Knowledge of sediment permeability is required for quantifying advection and associated solute transport, but studies of marine sediments typically report grain size analyses rather than permeability. Here data from 23 studies were examined to determine the range in permeabilities reported for sublittoral marine sands and to assess the utility of permeability–grain size relationships in this setting. In the resulting database, the permeability of small (∼30 cm) undisturbed cores collected from the sea floor all fell between 2 × 10⁻¹² and 4 × 10⁻¹⁰ m², a range where advective transport induced by wave and current action should be pervasive. The range in grain size was very similar for near-shore (<10 m water depth) and continental shelf samples (>10 m water depth), but the permeability of the continental shelf samples was consistently lower for the same median grain size. Empirical permeability–grain size relationships generated a poor fit (r² = 0.35) for the aggregate data, but separate relationships for near-shore and continental shelf samples were significantly better, r² = 0.66 and 0.77, respectively. Permeability–grain size relationships thus may be useful for sublittoral sands, but a larger database needs to be accumulated before reliable fit parameters and variability can be predicted. Thus it is recommended that permeability be routinely determined when characterizing sedimentological properties of marine sand deposits. Concurrent determinations of sediment bulk density and porosity may further improve estimates of permeability.  相似文献   

Modeling of mesoscale coupled ocean–atmosphere interaction and its feedback to ocean in the western Arabian Sea     

Hyodae Seo  Raghu Murtugudde  Markus Jochum  Arthur J. Miller 《Ocean Modelling》2008,25(3-4):120-131

Observations of the western Arabian Sea over the last decade have revealed a rich filamentary eddy structure, with large horizontal SST gradients in the ocean, developing in response to the southwest monsoon winds. This summertime oceanic condition triggers an intense mesoscale coupled interaction, whose overall influence on the longer-term properties of this ocean remains uncertain. In this study, a high-resolution regional coupled model is employed to explore this feedback effect on the long-term dynamical and thermodynamical structure of the ocean.The observed relationship between the near-surface winds and mesoscale SSTs generate Ekman pumping velocities at the scale of the cold filaments, whose magnitude is the order of 1 m/day in both the model and observations. This additional Ekman-driven velocity, induced by the wind-eddy interaction, accounts for approximately 10–20% of oceanic vertical velocity of the cold filaments. This implies that Ekman pumping arising from the mesoscale coupled feedback makes a non-trivial contribution to the vertical structure of the upper ocean and the evolution of mesoscale eddies, with obvious implications for marine ecosystem and biogeochemical variability.Furthermore, SST features associated with cold filaments substantially reduce the latent heat loss. The long-term latent heat flux change due to eddies in the model is approximately 10–15 W/m² over the cold filaments, which is consistent with previous estimates based on short-term in situ measurements. Given the shallow mixed layer, this additional surface heat flux warms the cold filament at the rate of 0.3–0.4 °C/month over a season with strong eddy activity, and 0.1–0.2 °C/month over the 12-year mean, rendering overall low-frequency modulation of SST feasible. This long-term mixed layer heating by the surface flux is approximately ±10% of the lateral heat flux by the eddies, yet it can be comparable to the vertical heat flux. Potential dynamic and thermodynamic impacts of this observed air–sea interaction on the monsoons and regional climate are yet to be quantified given the strong correlation between the Somalia upwelling SST and the Indian summer monsoons.  相似文献   

Spatial variations in surface water methane super-saturation and emission in Lake Lugano,southern Switzerland     

Jan Blees  Helge Niemann  Markus Erne  Jakob Zopfi  Carsten J. Schubert  Moritz F. Lehmann 《Aquatic Sciences - Research Across Boundaries》2015,77(4):535-545

  相似文献   

Impacts of climate change in three hydrologic regimes in British Columbia,Canada   总被引：1，自引：0，他引：1       下载免费PDF全文

Markus Schnorbus  Arelia Werner  Katrina Bennett 《水文研究》2014,28(3):1170-1189

Hydrologic modelling has been applied to assess the impacts of projected climate change within three study areas in the Peace, Campbell and Columbia River watersheds of British Columbia, Canada. These study areas include interior nival (two sites) and coastal hybrid nival–pluvial (one site) hydro‐climatic regimes. Projections were based on a suite of eight global climate models driven by three emission scenarios to project potential climate responses for the 2050s period (2041–2070). Climate projections were statistically downscaled and used to drive a macro‐scale hydrology model at high spatial resolution. This methodology covers a large range of potential future climates for British Columbia and explicitly addresses both emissions and global climate model uncertainty in the final hydrologic projections. Snow water equivalent is projected to decline throughout the Peace and Campbell and at low elevations within the Columbia. At high elevations within the Columbia, snow water equivalent is projected to increase with increased winter precipitation. Streamflow projections indicate timing shifts in all three watersheds, predominantly because of changes in the dynamics of snow accumulation and melt. The coastal hybrid site shows the largest sensitivity, shifting to more rainfall‐dominated system by mid‐century. The two interior sites are projected to retain the characteristics of a nival regime by mid‐century, although streamflow‐timing shifts result from increased mid‐winter rainfall and snowmelt, and earlier freshet onset. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

Keynote address: Outstanding problems in solar physics     

Markus J. Aschwanden 《Journal of Astrophysics and Astronomy》2008,29(1-2):3-16

Celebrating the diamond jubilee of the Physics Research Laboratory (PRL) in Ahmedabad, India, we look back over the last six decades in solar physics and contemplate on the ten outstanding problems (or research foci) in solar physics:

1. The solar neutrino problem
2. Structure of the solar interior (helioseismology)
3. The solar magnetic field (dynamo, solar cycle, corona)
4. Hydrodynamics of coronal loops
5. MHD oscillations and waves (coronal seismology)
6. The coronal heating problem
7. Self-organized criticality (from nanoflares to giant flares)
8. Magnetic reconnection processes
9. Particle acceleration processes
10. Coronal mass ejections and coronal dimming

The first two problems have been largely solved recently, while the other eight selected problems are still pending a final solution, and thus remain persistent Challenges for Solar Cycle 24, the theme of this jubilee conference.  相似文献   

Exploring debris‐flow history and process dynamics using an integrative approach on a dolomitic cone in western Austria     

Emily Procter  Markus Stoffel  Michelle Schneuwly‐Bollschweiler  Mathias Neumann 《地球表面变化过程与地形》2012,37(9):913-922

The evolution of a debris‐flow cone depends on a multitude of factors in the hydrogeomorphic system. Investigations of debris‐flow history and cone dynamics in highly active catchments therefore require an integrative approach with a temporal and spatial resolution appropriate for the goals of the study. We present the use of an orthophoto time series to augment standard dendrogeomorphic techniques to describe the spatio‐temporal dynamics of debris flows on a highly active cone in the western Austrian Alps. Analysis of seven orthophotos since 1951 revealed a migration of active deposition areas with a resulting severe loss of forest cover (> 80%) and a mean tree loss per year of 10·4 (range 1·3–16·6 trees per year). Analysis of 193 Pinus mugo ssp. uncinata trees allowed the identification of 161 growth disturbances corresponding to 16 debris flows since 1839 and an average decadal frequency of 0·9 events. As a result of the severe loss of forest cover, we speculate that < 20% of the more recent events were actually captured in the tree‐ring record, giving a decadal return interval of ~7·5 events for a period of 60 years. Based on three annual field observations, it is evident that this catchment (the Bärenrüfe) produces very frequent (< 1 yr), small (in the order of a few 10 to 100 m³) debris flows with minor material relocation. The specific challenges of tree‐ring analysis in this tree species and in highly active environments are explicitly addressed in the discussion and underline the necessity of employing complementary methods of analysis in an integrative manner. Copyright © 2012 John Wiley & Sons, Ltd.  相似文献   

A large wet snow avalanche cycle in West Greenland quantified using remote sensing and in situ observations     

Abermann  Jakob  Eckerstorfer  Markus  Malnes  Eirik  Hansen  Birger Ulf 《Natural Hazards》2019,97(2):517-534

Natural Hazards - On 11 April 2016 we observed high slushflow and wet snow avalanche activity at the environmental monitoring station Kobbefjord in W-Greenland. Snow avalanches released as a result...  相似文献   

Coupling the Xinanjiang model to a kinematic flow model based on digital drainage networks for flood forecasting   总被引：1，自引：0，他引：1  

Jintao Liu  Xi Chen  Jiabao Zhang  Markus Flury 《水文研究》2009,23(9):1337-1348

The Xinanjiang model, which is a conceptual rainfall‐runoff model and has been successfully and widely applied in humid and semi‐humid regions in China, is coupled by the physically based kinematic wave method based on a digital drainage network. The kinematic wave Xinanjiang model (KWXAJ) uses topography and land use data to simulate runoff and overland flow routing. For the modelling, the catchment is subdivided into numerous hillslopes and consists of a raster grid of flow vectors that define the water flow directions. The Xinanjiang model simulates the runoff yield in each grid cell, and the kinematic wave approach is then applied to a ranked raster network. The grid‐based rainfall‐runoff model was applied to simulate basin‐scale water discharge from an 805‐km² catchment of the Huaihe River, China. Rainfall and discharge records were available for the years 1984, 1985, 1987, 1998 and 1999. Eight flood events were used to calibrate the model's parameters and three other flood events were used to validate the grid‐based rainfall‐runoff model. A Manning's roughness via a linear flood depth relationship was suggested in this paper for improving flood forecasting. The calibration and validation results show that this model works well. A sensitivity analysis was further performed to evaluate the variation of topography (hillslopes) and land use parameters on catchment discharge. Copyright © 2009 John Wiley & Sons, Ltd.  相似文献   

Dating of soil layers in a young floodplain using iron oxide crystallinity   总被引：1，自引：0，他引：1  

Georg J. Lair  Franz Zehetner  Markus Hrachowitz  Nikolaus Franz  Franz-Josef Maringer  Martin H. Gerzabek 《Quaternary Geochronology》2009,4(3):260-266

Dating of fluvial deposits is essential for a more quantitative understanding of landscape evolution and soil development in floodplain environments. We collected soil layers in defined depth intervals down to 60 cm along a substrate age gradient in a floodplain of the Danube River near Vienna, Austria. Depth profiles of fallout ¹³⁷Cs were used to assess short-term sedimentation, and optically stimulated luminescence (OSL) dating was used to attribute sediment deposits to time periods between the early last millennium BC and the 18th century AD. In the studied soils, the ratio of oxalate- to dithionite-extractable iron (Fe_o/Fe_d), which indicates the degree of iron oxide crystallinity, progressively decreased from ratios greater than 0.5 to values less than 0.2 with increasing soil age and proved to be a reliable indicator of soil maturity. We linked the observed Fe_o/Fe_d ratios to the radiometric and OSL ages in a chronofunction, which allows to approximately date soil layers that lack an independent age control. The soil ages calculated with this chronofunction accurately reflected their geomorphological position, resulted in consistent age trends with depth, and highlighted the active morphodynamics of the studied floodplain. The chronofunction was further validated by dating a soil profile near the studied chronosequence that contained an archaeological find dated to the La Tène period (5th to 1st century BC).  相似文献