Observation of fluid parcel pathways in the Kuroshio Stream revealed a striking crossstream pattern associated with the Kuroshio‘‘ s meanders. In order to understand the observed pattern, a two-dimensional kinematic model of a meandering jet was developed which could be used to examine the relationship between streamfunction patterns and fluid parcel trajectories. The experiments designed to investigate the dependence of the water exchanges between the Kuroshio water and its surroundings on the characteristics of the Kuroshio‘‘s meanders involved the downstream speed,phase speed and the amplitude of other propagating waves. The results suggested that fluid parcels could cross the meandering jet to and fro; and that the water exchanges between the Kuroshio and its surroundings increased with a) increasing meander amplitude, b) decreasing downstream speed, and c) increasing wave phase speed. The results also showed that when the meandering jet was disturbed by other propagating waves, more effective water exchanges could be induced. 相似文献
Darwin is a cornerstone mission of the Horizons 2000+ program of the European Space Agency. It has the express purpose of
carrying out the first direct search for terrestrial exoplanets, and to achieve unprecedented spatial resolution in the infrared wavelength region. The
detection and study of terrestrial exoplanets promises to usher in a new era in science and will affect a broad spectrum of
disciplines. Further, the time line for implementation of such an instrument is now likely to be of the close order of 10
years, leading to possible answers to one of mankind's most fundamental questions in the second decade of the 21st century.
It has been found that in order to realize am interferometer in space in the next 10–15 years, it is necessary to prepare
the way through a number of intermediary steps – both on the ground and in space. In this context, we here describe GENIE
– a ground based nulling interferometry experiment to be implemented at the VLTI in a partnership between ESA and ESO.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献
1Water LossInitiativesUnaccounted-for water(or unbilled water)has beenreceiving newscrutiny at both the state and nationallevels.For years,water conservationeffortsin Europehave emphasized reduction in water loss to a muchgreater extent thaninthe United S… 相似文献
Uranium-series dating of oxygen and carbon isotope records for stalagmite SJ3 collected in Songjia Cave, central China, shows significant variation in past climate and environment during the period 20-10 ka. Stalagmite SJ3 is located more than 1000 km inland of the coastal Hulu Cave in East China and more than 700 km north of the Dongge Cave in Southwest China and, despite minor differences, displays a clear first-order similarity with the Hulu and Dongge records. The coldest climatic phase since the Last Glacial Maximum, which is associated with the Heinrich Event 1 in the North Atlantic region, was clearly recorded in SJ3 between 17.6 and 14.5 ka, in good agreement in timing, duration and extent with the records from Hulu and Dongge caves and the Greenland ice core. The results indicate that there have been synchronous and significant climatic changes across monsoonal China and strong teleconnections between the North Atlantic and East Asia regions during the period 20-10 ka. This is much different from the Holocene Optimum which shows a time shift of more than several thousands years from southeast coastal to inland China. It is likely that temperature change at northern high latitudes during glacial periods exerts stronger influence on the Asian summer monsoon relative to insolation and appears to be capable of perturbing large-scale atmospheric/oceanic circulation patterns in the Northern Hemisphere and thus monsoonal rainfall and paleovegetation in East Asia. Climatic signals in the North Atlantic region propagate rapidly to East Asia during glacial periods by influencing the winter land-sea temperature contrast in the East Asian monsoon region. 相似文献
We designed a new seismic source model for Italy to be used as an input for country-wide probabilistic seismic hazard assessment (PSHA) in the frame of the compilation of a new national reference map.
We started off by reviewing existing models available for Italy and for other European countries, then discussed the main open issues in the current practice of seismogenic zoning.
The new model, termed ZS9, is largely based on data collected in the past 10 years, including historical earthquakes and instrumental seismicity, active faults and their seismogenic potential, and seismotectonic evidence from recent earthquakes. This information allowed us to propose new interpretations for poorly understood areas where the new data are in conflict with assumptions made in designing the previous and widely used model ZS4.
ZS9 is made out of 36 zones where earthquakes with Mw > = 5 are expected. It also assumes that earthquakes with Mw up to 5 may occur anywhere outside the seismogenic zones, although the associated probability is rather low. Special care was taken to ensure that each zone sampled a large enough number of earthquakes so that we could compute reliable earthquake production rates.
Although it was drawn following criteria that are standard practice in PSHA, ZS9 is also innovative in that every zone is characterised also by its mean seismogenic depth (the depth of the crustal volume that will presumably release future earthquakes) and predominant focal mechanism (their most likely rupture mechanism). These properties were determined using instrumental data, and only in a limited number of cases we resorted to geologic constraints and expert judgment to cope with lack of data or conflicting indications. These attributes allow ZS9 to be used with more accurate regionalized depth-dependent attenuation relations, and are ultimately expected to increase significantly the reliability of seismic hazard estimates. 相似文献
The imbalance between incoming and outgoing salt causes salinization of soils and sub-soils that result in increasing the
salinity of stream-flows and agriculture land. This salinization is a serious environmental hazard particularly in semi-arid
and arid lands. In order to estimate the magnitude of the hazard posed by salinity, it is important to understand and identify
the processes that control salt movement from the soil surface through the root zone to the ground water and stream flows.
In the present study, Malaprabha sub-basin (up to dam site) has been selected which has two distinct climatic zones, sub-humid
(upstream of Khanapur) and semi-arid region (downstream of Khanapur). In the upstream, both surface and ground waters are
used for irrigation, whereas in the downstream mostly groundwater is used. Both soils and ground waters are more saline in
downstream parts of the study area. In this study we characterized the soil salinity and groundwater quality in both areas.
An attempt is also made to model the distribution of potassium concentration in the soil profile in response to varying irrigation
conditions using the SWIM (Soil-Water Infiltration and Movement) model. Fair agreement was obtained between predicted and
measured results indicating the applicability of the model. 相似文献