The auroral O+ non-Maxwellian velocity distribution function revisited     

D. Hubert  F. Leblanc 《Annales Geophysicae》1997,15(2):249-254

New characteristics of O⁺ ion velocity distribution functions in a background of atomic oxygen neutrals subjected to intense external electromagnetic forces are presented. The one dimensional (1-D) distribution function along the magnetic field displays a core-halo shape which can be accurately fitted by a two Maxwellian model. The Maxwellian shape of the 1-D distribution function around a polar angle of 21 ± 1° from the magnetic field direction is confirmed, taking into account the accuracy of the Monte Carlo simulations. For the first time, the transition of the O⁺ 1-D distribution function from a core halo shape along the magnetic field direction to the well-known toroidal shape at large polar angles, through the Maxwellian shape at polar angle of 21 ± 1° is properly explained from a generic functional of the velocity moments at order 2 and 4.  相似文献   

Ambiguity in Measuring Matrix Diffusion with Single-Well Injection/Recovery Tracer Tests   总被引：2，自引：0，他引：2  

Steven C. Lessoff  Leonard F. Konikow 《Ground water》1997,35(1):166-176

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Analyses of Slug Tests and Hydraulic Conductivity Variations in the Near Field of a Two-Well Tracer Experiment Site     

Josep Mas-Pla  T.-C. Jim Yeh  Thomas M. Williams  John F. McCarthy 《Ground water》1997,35(3):492-501

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Wasser – der bedrohte Lebensstoff Ein Element in der Krise. Hrsg.: D. Beste,M. Kälke VDI-Buch. Springer-Verlag. Berlin, 1996, ISBN 3-540-62741-3, 191 S., brosch., DM 24,80     

F. H. Frimmel 《洁净——土壤、空气、水》1997,25(4):225-225

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Ein kompetitiver Immunoassay zur Bestimmung des Herbizids Fluazifop in Trink- und Grundwasser     

F. Poppe  K. Rubach 《洁净——土壤、空气、水》1997,25(5):265-267

A Competitive Immunoassay for the Determination of the Herbicide Fluazifop in Drinking Water and Groundwater A competitive solid-phase enzyme immunoassay using rabbit polyclonal antibodies was developed for the detection of the herbicide fluazifop [(RS)-2-[4-(5-trifluoromethyl-2-pyridyloxy)phenoxy]propionic acid] in drinking water and groundwater. Present regulatory limits for drinking water in Germany were taken as the critical level. The carrier protein was bovine serum albumin; horseradish peroxidase was used as marker enzyme with 3,3′,5,5′-tetramethylbenzidine as substrate. A high concentration of high-affinity antibodies in the serum, optimization of test conditions (antibody and enzyme tracer concentration, incubation time etc.), and very low cross reactivities to substances of similar structures led to a highly sensitive and specific ELISA with a detection limit below 0.1 μg/L for fluazifop as free acid. On testing the suitability of the assay's use as a screening test with one hundred drinking-water samples, the three samples which had been spiked in the laboratory were recognized as positive with respect to their fluazifop content. Confirmation by gas chromatography-mass spectrometry showed the test results of two other samples to be false positive. False negative results did not appear. The concentration was in the detection limit region of 0.1 μg/L.  相似文献   

The nonlinear association between ENSO and the Euro-Atlantic winter sea level pressure   总被引：1，自引：0，他引：1  

Aiming Wu  William W. Hsieh 《Climate Dynamics》2004,23(7-8):859-868

A nonlinear projection of the tropical Pacific sea surface temperature anomalies (SSTA) onto the Northern Hemisphere winter sea level pressure (SLP) anomalies by neural networks (NN) was performed to investigate the nonlinear association between El Niño-Southern Oscillation (ENSO) and the Euro-Atlantic winter climate. While the linear impact of ENSO on the Euro-Atlantic winter SLP is weak, the NN projection reveals statistically significant SLP anomalies over the Euro-Atlantic sector during both extreme cold and warm ENSO episodes, suggesting that the Euro-Atlantic climate mainly responds to ENSO nonlinearly. The nonlinear response, mainly a quadratic response to the SSTA, reveals that regardless of the sign of the SSTA, positive SLP anomalies are found over the North Atlantic, stretching from eastern Canada to Europe (with anomaly center located just northwestward of Portugal), and negative anomalies centered over Scandinavia and Norwegian Sea, consistent with the excitation of the positive North Atlantic Oscillation pattern.  相似文献   

Mitigating the Effects of Climate Change on the Water Resources of the Columbia River Basin   总被引：5，自引：3，他引：5  

Jeffrey T. Payne  Andrew W. Wood  Alan F. Hamlet  Richard N. Palmer  Dennis P. Lettenmaier 《Climatic change》2004,62(1-3):233-256

The potential effects of climate change on the hydrology and water resources of the Columbia River Basin (CRB) were evaluated using simulations from the U.S. Department of Energy and National Center for Atmospheric Research Parallel Climate Model (DOE/NCAR PCM). This study focuses on three climate projections for the 21st century based on a `business as usual' (BAU) global emissions scenario, evaluated with respect to a control climate scenario based on static 1995 emissions. Time-varying monthly PCM temperature and precipitation changes were statistically downscaled and temporally disaggregated to produce daily forcings that drove a macro-scale hydrologic simulation model of the Columbia River basin at 1/4-degree spatial resolution. For comparison with the direct statistical downscaling approach, a dynamical downscaling approach using a regional climate model (RCM) was also used to derive hydrologic model forcings for 20-year subsets from the PCM control climate (1995–2015) scenario and from the three BAU climate(2040–2060) projections. The statistically downscaled PCM scenario results were assessed for three analysis periods (denoted Periods 1–3: 2010–2039,2040–2069, 2070–2098) in which changes in annual average temperature were +0.5,+1.3 and +2.1 °C, respectively, while critical winter season precipitation changes were –3, +5 and +1 percent. For RCM, the predicted temperature change for the 2040–2060 period was +1.2 °C and the average winter precipitation change was –3 percent, relative to the RCM controlclimate. Due to the modest changes in winter precipitation, temperature changes dominated the simulated hydrologic effects by reducing winter snow accumulation, thus shifting summer streamflow to the winter. The hydrologic changes caused increased competition for reservoir storage between firm hydropower and instream flow targets developed pursuant to the Endangered Species Act listing of Columbia River salmonids. We examined several alternative reservoir operating policies designed to mitigate reservoir system performance losses. In general, the combination of earlier reservoir refill with greater storage allocations for instream flow targets mitigated some of the negative impacts to flow, but only with significant losses in firm hydropower production (ranging from –9 percent in Period1 to –35 percent for RCM). Simulated hydropower revenue changes were lessthan 5 percent for all scenarios, however, primarily due to small changes inannual runoff.  相似文献   

The Effects of Climate Change on Water Resources in the West: Introduction and Overview     

Tim Barnett  Robert Malone  William Pennell  Detlet Stammer  Bert Semtner  Warren Washington 《Climatic change》2004,62(1-3):1-11

The results of an experimental `end to end' assessment of the effects of climate change on water resources in the western United States are described. The assessment focuses on the potential effects of climate change over the first half of the 21st century on the Columbia, Sacramento/San Joaquin, and Colorado river basins. The paper describes the methodology used for the assessment, and it summarizes the principal findings of the study. The strengths and weaknesses of this study are discussed, and suggestions are made for improving future climate change assessments.  相似文献   

How Important is Global Warming for Coastal Erosion?     

Marcel J. F. Stive 《Climatic change》2004,64(1-2):27-39

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Estimation of Site Effects in Beijing City   总被引：6，自引：0，他引：6  

Z. Ding  Y. T. Chen  G. F. Panza 《Pure and Applied Geophysics》2004,161(5-6):1107-1123

— For the realistic modeling of the seismic ground motion in lateral heterogeneous anelastic media, the database of 3-D geophysical structures for Beijing City has been built up to model the seismic ground motion in the City, caused by the 1976 Tangshan and the 1998 Zhangbei earthquakes. The hybrid method, which combines the modal summation and the finite-difference algorithms, is used in the simulation. The modeling of the seismic ground motion, for both the Tangshan and the Zhangbei earthquakes, shows that the thick Quaternary sedimentary cover amplifies the peak values and increases the duration of the seismic ground motion in the northwestern part of the City. Therefore the thickness of the Quaternary sediments in Beijing City is the key factor controling the local ground effects. Four zones are defined on the base of the different thickness of the Quaternary sediments. The response spectra for each zone are computed, indicating that peak spectral values as high as 0.1 g are compatible with past seismicity and can be well exceeded if an event similar to the 1697 Sanhe-Pinggu occurs.  相似文献