Abiotic Stream Classification as a Basis for a Surveillance Monitoring Network in Austria in Accordance with the EU Water Framework Directive     

R. Wimmer  A. Chovanec  O. Moog  M. H. Fink  D. Gruber 《洁净——土壤、空气、水》2000,28(4):177-184

This study presents the 26 major surface water types established in Austria in accordance with the draft of the EU Water Framework Directive (WFD). These types are made up of so‐called aquatic landscape units and large rivers. The 17 aquatic landscape units were defined using a database in which all Austrian running waters with a catchment area greater than 10 km^[2] were described according to the following typological features: size of catchment area, altitude of catchment area and confluences, stream order, geology, zoogeographical regions (ecoregions), and subregions. At running waters with gauges, a classification according to flow regimes was carried out. Large rivers were defined as running waters with a stream order ⩾7 and/or a catchment area > 2500 km² and/or with an average flow >50 m³/s. These major types represent, inter alia, the basis for the establishment of a surveillance monitoring network as required by the WFD.  相似文献   

Earth System Mass Transport Mission (e.motion): A Concept for Future Earth Gravity Field Measurements from Space   总被引：1，自引：0，他引：1  

I. Panet  J. Flury  R. Biancale  T. Gruber  J. Johannessen  M. R. van den Broeke  T. van Dam  P. Gegout  C. W. Hughes  G. Ramillien  I. Sasgen  L. Seoane  M. Thomas 《Surveys in Geophysics》2013,34(2):141-163

In the last decade, satellite gravimetry has been revealed as a pioneering technique for mapping mass redistributions within the Earth system. This fact has allowed us to have an improved understanding of the dynamic processes that take place within and between the Earth’s various constituents. Results from the Gravity Recovery And Climate Experiment (GRACE) mission have revolutionized Earth system research and have established the necessity for future satellite gravity missions. In 2010, a comprehensive team of European and Canadian scientists and industrial partners proposed the e.motion (Earth system mass transport mission) concept to the European Space Agency. The proposal is based on two tandem satellites in a pendulum orbit configuration at an altitude of about 370 km, carrying a laser interferometer inter-satellite ranging instrument and improved accelerometers. In this paper, we review and discuss a wide range of mass signals related to the global water cycle and to solid Earth deformations that were outlined in the e.motion proposal. The technological and mission challenges that need to be addressed in order to detect these signals are emphasized within the context of the scientific return. This analysis presents a broad perspective on the value and need for future satellite gravimetry missions.  相似文献   

Mass,Volume and Velocity of the Antarctic Ice Sheet: Present-Day Changes and Error Effects     

A. Groh  H. Ewert  R. Rosenau  E. Fagiolini  C. Gruber  D. Floricioiu  W. Abdel Jaber  S. Linow  F. Flechtner  M. Eineder  W. Dierking  R. Dietrich 《Surveys in Geophysics》2014,35(6):1481-1505

This study examines present-day changes of the Antarctic ice sheet (AIS) by means of different data sets. We make use of monthly gravity field solutions acquired by the Gravity Recovery and Climate Experiment (GRACE) to study mass changes of the AIS for a 10-year period. In addition to ‘standard’ solutions of release 05, solutions based on radial base functions were used. Both solutions reveal an increased mass loss in recent years. For a 6-year period surface-height changes were inferred from laser altimetry data provided by the Ice, Cloud, and land Elevation Satellite (ICESat). The basin-scale volume trends were converted into mass changes and were compared with the GRACE estimates for the same period. Focussing on the Thwaites Glacier, Landsat optical imagery was utilised to determine ice-flow velocities for a period of more than two decades. This data set was extended by means of high-resolution synthetic aperture radar (SAR) data from the TerraSAR-X mission, revealing an accelerated ice flow of all parts of the glacier. ICESat data over the Thwaites Glacier were complemented by digital elevation models inferred from TanDEM-X data. This extended data set exhibits an increased surface lowering in recent times. Passive microwave remote sensing data prove the long-term stability of the accumulation rates in a low accumulation zone in East Antarctica over several decades. Finally, we discuss the main error sources of present-day mass-balance estimates: the glacial isostatic adjustment effect for GRACE as well as the biases between laser operational periods and the volume–mass conversion for ICESat.  相似文献   

Comparison of Daily GRACE Gravity Field and Numerical Water Storage Models for De-aliasing of Satellite Gravimetry Observations   总被引：1，自引：0，他引：1  

L. Zenner  I. Bergmann-Wolf  H. Dobslaw  T. Gruber  A. Güntner  M. Wattenbach  S. Esselborn  R. Dill 《Surveys in Geophysics》2014,35(6):1251-1266

Reducing aliasing effects of insufficiently modelled high-frequent, non-tidal mass variations of the atmosphere, the oceans and the hydrosphere in gravity field models derived from the Gravity Recovery and Climate Experiment (GRACE) satellite mission is the topic of this study. The signal content of the daily GRACE gravity field model series (ITG-Kalman) is compared to high-frequency bottom pressure variability and terrestrially stored water variations obtained from recent numerical simulations from an ocean circulation model (OMCT) and two hydrological models (WaterGAP Global Hydrology Model, Land Surface Discharge Model). Our results show that daily estimates of ocean bottom pressure from the most recent OMCT simulations and the daily ITG-Kalman solutions are able to explain up to 40 % of extra-tropical sea-level variability in the Southern Ocean. In contrast to this, the daily ITG-Kalman series and simulated continental total water storage variability largely disagree at periods below 30 days. Therefore, as long as no adequate hydrological model will become available, the daily ITG-Kalman series can be regarded as a good initial proxy for high-frequency mass variations at a global scale. As a second result of this study, based on monthly solutions as well as daily observation residuals, it is shown that applying this GRACE-derived de-aliasing model supports the determination of the time-variable gravity field from GRACE data and the subsequent geophysical interpretation. This leads us to the recommendation that future satellite concepts for determining mass variations in the Earth system should be capable of observing higher frequeny signals with sufficient spatial resolution.  相似文献   

Detrital Remanence, Inclination Errors, and Anhysteretic Remanence Anisotropy: Quantitative Model and Experimental Results   总被引：1，自引：0，他引：1  

Michael J. Jackson  Subir K. Banerjee  James A. Marvin  Ran Lu  William Gruber 《Geophysical Journal International》1991,104(1):95-103

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Jupiter's non Io-related decametric radiation     

Georg M. Gruber 《Astrophysics and Space Science》1975,37(1):169-172

A correlation study between solar wind activity and Jupiter's decametric radiation seems to indicate that the solar wind has a suppressive effect on the non Io-related emission. A basic model for the non Io-related emission is presented, to explain this and other characteristics of the non Io-related emission.  相似文献   

Rock falls in the Mont Blanc Massif in 2007 and 2008   总被引：1，自引：1，他引：0  

Ludovic Ravanel  Françoise Allignol  Philip Deline  Stephan Gruber  Mario Ravello 《Landslides》2010,7(4):493-501

Due to a lack of systematic observations, the intensity and volume of rock falls and rock avalanches in high mountain areas are still poorly known. Nevertheless, these phenomena could have burly consequences. To document present rock falls, a network of observers (guides, mountaineers, and hut wardens) was initiated in the Mont Blanc Massif in 2005 and became fully operational in 2007. This article presents data on the 66 rock falls (100 m³?≤?V?≤?50,000 m³) documented in 2007 (n?=?41) and 2008 (n?=?25). Most of the starting zones are located in warm permafrost areas, which are most sensitive to warming, and only four rock falls are clearly out of permafrost area. Different elements support permafrost degradation as one of the main triggering factors of present rock falls in high mountain areas.  相似文献   

Biological and physical impacts of ageostrophic frontal circulations driven by confluent flow and vertical mixing     

Takeyoshi Nagai  Amit Tandon  Nicolas Gruber  James C. McWilliams 《Dynamics of Atmospheres and Oceans》2008,45(3-4):229

Subduction, upwelling, and phytoplankton blooms are commonly observed features at oceanic fronts. This study isolates the role of vertical mixing for enhanced production and water mass subduction near fronts, considering the time-developing problem with a Semi-Geostrophic circulation model coupled to a planktonic ecosystem model. Our model results show that vertical mixing in the surface boundary layer strongly modifies the time evolution of the front and of its associated biology. Ageostrophic flows caused by the combined effects of confluence and vertical mixing enhance primary production on the less dense side and increase water mass subduction on the dense side of the front. Confluence alone results in the intensification of the front by the same advective response, while the phytoplankton bloom on the less dense side does not arise without vertical mixing. Vertical mixing alone slumps the front near the surface and provides weak subduction on the dense side and uplift of the isopycnals at the center of the front. We find that it is possible to sustain an isolated phytoplankton patch above the domed isopycnals at the center of the front with the nutrients supplied by the secondary circulations arising due to vertical mixing. These results suggest that the phytoplankton bloom and patches found on the less dense side of fronts in many field observations are likely caused by fine-scale along-isopycnal upwelling of nutrients forced by adiabatic confluence in the meander trough of fronts and further pumping and entrainment of nutrients by the secondary circulation due to vertical mixing. Isolated patches observed at the center of the front in many frontal surveys could be caused by secondary flows due to vertical mixing.  相似文献   

Assessing water quality in Marine Protected Areas from Southern California, USA     

Schiff K  Luk B  Gregorio D  Gruber S 《Marine pollution bulletin》2011,62(12):2780-2786

Despite the regulatory mandate to maintain “natural water quality”, there are ?271 storm drain discharges that potentially threaten the 14 designated marine water quality protected areas in Southern California called Areas of Special Biological Significance (ASBS). After sampling 35 site-events, the geomean concentrations of total suspended solids, nutrients, total and dissolved trace metals, and polycyclic aromatic hydrocarbons in the ocean following storm events were similar between reference drainages and ASBS discharge sites. Concentrations of chlorinated hydrocarbons were nondetectable and no post-storm sample exhibited significant toxicity to the endemic purple sea urchin (Strongylocentrotus purpuratus) near ASBS discharge sites. A reference-based threshold was developed and, despite the similarities in average concentrations, there were some individual ASBS discharge sites that were greater than reference background. Cumulatively across all ASBS, the constituents that were most frequently greater than the reference-based threshold were nutrients and general constituents, followed by dissolved and total trace metals.  相似文献   

Optimal orbits for temporal gravity recovery regarding temporal aliasing     

Michael Murböck  Roland Pail  Ilias Daras  Thomas Gruber 《Journal of Geodesy》2014,88(2):113-126

The temporal changes of the Earth’s gravity field can be observed on a global scale with low–low satellite-to-satellite tracking (SST) missions. One of the largest restrictions of the quality of low–low SST gravity fields is temporal aliasing. This study investigates the design of optimal satellite orbits for temporal gravity retrieval regarding temporal aliasing. We present a method with which optimal altitudes for the orbit of a gravity satellite mission with the goal of temporal gravity retrieval can be identified. The two basic orbit frequencies, the rates of the argument of the latitude and the ascending node, determine the mapping of the signal measured along the orbit onto the spherical harmonic (SH) spectrum. The main spectral characteristics of temporal aliasing are maxima at specific SH orders. The magnitude of the effects depends on the basic frequencies. This is analyzed with numerical low–low SST closed-loop simulations including both tidal and non-tidal background models and GRACE-like observation noise. Analyses of actual monthly GRACE solutions show that these characteristics do not depend on the low–low SST processing method. Optimal orbits are found in specific altitude bands. The best altitude bands regarding temporal aliasing for polar low Earth orbiters (LEOs) are around 301, 365, 421 and 487 km. In these bands, major aliasing effects do not occur for SH degrees and orders below 70. This study gives unique and in-depth insights into the mechanism of temporal aliasing. As it provides an important orbit design approach, it is independent of any (post-) processing method to reduce temporal aliasing.  相似文献