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31.
Jürg Trösch Giorgio Salvadè Kurt Stocker 《Aquatic Sciences - Research Across Boundaries》1987,49(1):16-28
The northern and the southern basin of Lake Lugano, Switzerland, are separated by an artificial dam. The flow of the water
is not only influenced by the outflow of the northern basin but also by gravitational oscillations (seiches) of both basins.
A longperiodic peak around 100 minutes can be explained by a mathematical model. The interaction of the internal waves is
a coupled oscillation with a period of 74 hours.
相似文献
32.
Statistical time series decomposition into significant components and application to European temperature 总被引:1,自引:0,他引:1
Summary
Time series of observed monthly mean temperatures of European stations and at grid points are decomposed into different kinds
of trends (linear, progressive, degressive), constant or significantly changing annual cycles, episodic and harmonic components,
extreme events and noise. A stepwise regression is used to test whether the components are significant. Special emphasis is
given to extreme events which we distinguish from extreme values. While extreme values may likely occur by chance, it is very
unlikely that extreme events would be in accordance with the features of the time series. On one hand, extreme events alter
the estimates (and test results) of trends and other components. On the other hand, such components have to be known to recognize
extreme events. To deal with this problem, an iterative procedure is introduced that converges fast to robust estimates of
all the components.
Applying this procedure to the last 100 years of European temperatures reveals that the phase of the annual cycle is shifted
backward within the year in western Europe but foreward in eastern Europe. In the latter region, the amplitude of the annual
cycle has also increased significantly. Most of the trend components found in the time series are positive and linear. Nearly
all detected extreme events are cold events which occurred in winter. Their number has significantly grown. Significant harmonic
components with a period of 92.3 months (about 7.7 years) are found mainly in northern and western Europe.
Received August 15, 2000 Revised June 20, 2001 相似文献
33.
B.N. Maehlum K. Måseide K. Aarsnes A. Egeland B. Grandal J. Holtet T.A. Jacobsen N.C. Maynard F. Søraas J. Stadsnes E.V. Thrane J. Trøim 《Planetary and Space Science》1980,28(3):259-278
A “mother-daughter” rocket was launched from Andøya, Norway, February 1 1976 over two auroral structures. The “daughter” payload carried a 10keV electron accelerator and the “mother” carried a series of diagnostic instruments for monitoring optical and wave effects generated through beam-atmospheric interactions and production of secondary electrons.The experimental details are presented in this paper together with a survey of some of the results. This paper is also intended as a reference for a series of accompanying papers. 相似文献
34.
Per-Einar Trften 《Sedimentary Geology》2000,130(3-4):167-181
Geological structures suggest that the Fennoscandian Shield was subjected to a higher seismicity at the end of the last glaciation than today. This article demonstrates the use of varved clay chronology for dating paleoseismic events. It is argued that the deposited annually layered glacial varves were sensitive to past ground movements. In the Stockholm area, the Erstavik varved clay chronology suggests four paleoseismic events: a first (I) dating from varve year 10,473 to 10,468 BP; a second (II) 10,451 to 10,445 BP; a third (III) 10,429 to 10,425 BP; and a fourth (IV) 10,409 to 10,404 BP. In De Geer's ‘old' (1940) chronology the first (I) dating corresponds with −1117 to −1112, the second (II) with −1095 to −1089, the third (III) with −1073 to −1069, and the fourth (IV) with −1053 to −1048. The most pronounced event was the one at around varve year 10,429 BP (varve −1073 in De Geer's ‘old' chronology). The recurrence time of about 20 years suggests a totally different seismic regime at the time of deglaciation than what exists today. It coincided with the period of maximum isostatic uplift. The complexity of the varved clay response to seismic events is also discussed. 相似文献
35.
36.
Convective Boundary-Layer Entrainment: Short Review and Progress using Doppler Lidar 总被引:2,自引:2,他引:0
The entrainment of air from the free atmosphere into the convective boundary layer is reviewed and further investigated using
observations from a 2 μm Doppler lidar. It is possible to observe different individual processes entraining air into the turbulent
layer, which develop with varying stability of the free atmosphere. These different processes are attended by different entrainment-zone
thicknesses and entrainment velocities. Four classes of entrainment parametrizations, which describe relationships between
the fundamental parameters of the process, are examined. Existing relationships between entrainment-zone thickness and entrainment
velocity are basically confirmed using as scaling parameters boundary-layer height and convective velocity. An increase in
the correlation coefficient between stability parameters based on the stratification of the free atmosphere and entrainment
velocity (and entrainment-zone thickness respectively) up to 200% was possible using more suitable length and velocity scales. 相似文献
37.
Local climate change induced by groundwater overexploitation in a high Andean arid watershed,Laguna Lagunillas basin,northern Chile 总被引:2,自引:0,他引:2
The Laguna Lagunillas basin in the arid Andes of northern Chile exhibits a shallow aquifer and is exposed to extreme air temperature variations from 20 to ?25 °C. Between 1991 and 2012, groundwater levels in the Pampa Lagunillas aquifer fell from near-surface to ~15 m below ground level (bgl) due to severe overexploitation. In the same period, local mean monthly minimum temperatures started a declining trend, dropping by 3–8 °C relative to a nearby reference station. Meanwhile, mean monthly maximum summer temperatures shifted abruptly upwards by 2.7 °C on average in around 1996. The observed air temperature downturns and upturns are in accordance with detected anomalies in land-surface temperature imagery. Two major factors may be causing the local climate change. One is related to a water-table decline below the evaporative energy potential extinction depth of ~2 m bgl, which causes an up-heating of the bare soil surface and, in turn, influences the lower atmosphere. At the same time, the removal of near-surface groundwater reduces the thermal conductivity of the upper sedimentary layer, which consequently diminishes the heat exchange between the aquifer (constant heat source of ~10 °C) and the lower atmosphere during nights, leading to a severe dropping of minimum air temperatures. The observed critical water-level drawdown was 2–3 m bgl. Future and existing water-production projects in arid high Andean basins with shallow groundwater should avoid a decline of near-surface groundwater below 2 m bgl and take groundwater-climate interactions into account when identifying and monitoring potential environmental impacts. 相似文献
38.
Jochen Schanze Johanna Trümper Cornelia Burmeister Dirk Pavlik Ivan Kruhlov 《Environmental Earth Sciences》2012,65(5):1405-1414
The paper presents a methodology on how to consistently deal with the future change and management options in integrated water
resources management (IWRM). It is based on a conceptual framework with a five step procedure for the formulation and analysis
of a so-called ‘parameterised regional futures’. Developing and testing the approach for IWRM is realised for the upper part
of the Western Bug River catchment (Ukraine). Special attention is paid to scenarios of change covering climate and land use.
The future regional climate is downscaled with the model CCLM. Land cover is projected after retrospective change detection
and the derivation of prospective algorithms. Parameters of the interrelations between land use and the water cycle are tackled
through using the concept of the model PWF-LU. The methodology is currently being tested to analyse the impacts of mid-term
regional change and management options on the water cycle of the catchment. 相似文献
39.
W. Jaeschke T. Salkowski J. P. Dierssen J. T. Trümbach U. Krischke A. Günther 《Journal of Atmospheric Chemistry》1999,34(3):291-319
During two measuring campaigns in early spring 1994 and 1995 (March/April) and one campaign in summer 1994, measurements of ozone, PAN, sulfur dioxide, nitric acid, and particulate nitrate, sulfate, and ammonium (only 1995) were recorded in the Arctic. Observations were made by aircraft at various sites in the eastern and western Arctic. Ozone concentrations showed a steady increase with altitude both in spring and summer. During five flights in springtime, low ozone events (LOEs) could be observed near the surface and up to altitudes of 2000 m. SO2 background concentrations, ranging from detection limit (0.5 nmol/m3) to 5 nmol/m3, were observed during both spring and summer. Distinct maxima up to 55 nmol/m3 in lower altitudes were only obtained in springtime. Concentrations of the organic nitrate PAN were within a similar range as those of the inorganic nitrate HNO3 during spring campaigns. In contrast, concentrations of particulate nitrate were one half an order of magnitude lower. HNO3 concentrations increased significantly with altitude. Evidently, HNO3 was intruded from the stratosphere into the troposphere. Sulfate concentrations ranged between 5 and 30 nmol/m3; ammonium concentrations were obtained within a range from 10 to 50 nmol/m3. 相似文献
40.
Several cold vents are observed at the northern Cascadia margin offshore Vancouver Island in a 10 km2 region around Integrated Ocean Drilling Program Expedition 311 Site U1328. All vents are linked to fault systems that provide pathways for upward migrating fluids and at three vents methane plumes were detected acoustically in the water column. Downhole temperature measurements at Site U1328 revealed a geothermal gradient of 0.056 ± 0.004°C/m. With the measured in situ pore-water salinities the base of methane hydrate stability is predicted at 218–245 meters below seafloor. Heat-probe measurements conducted across Site U1328 and other nearby vents showed an average thermal gradient of 0.054 ± 0.004°C/m. Assuming that the bottom-simulating reflector (BSR) marks the base of the gas hydrate stability zone variations in BSR depths were used to investigate the linkages between the base of the gas hydrate stability zone and fluid migration. Variations in BSR depth can be attributed to lithology-related velocity changes or variations of in situ pore-fluid compositions. Prominent BSR depressions and reduced heat flow are seen below topographic highs, but only a portion of the heat flow reduction can be due to topography-linked cooling. More than half of the reduction may be due to thrust faulting or to pore-water freshening. Distinct changes in BSR depth below seafloor are observed at all cold vents studied and some portion of the observed decrease in the BSR depth was attributed to fault-related upwelling of warmer fluids. The observed decrease in BSR depth below seafloor underneath the vents ranges between 7 and 24 m (equivalent to temperature shifts of 0.07–0.15°C). 相似文献