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171.
The possible effects of trace-gas induced climatic changes on Pyramid and Yellowstone Lakes are assessed using a model of lake temperature. The model is driven by
years of hourly meteorological data obtained directly from the output of double-CO2 experiments (2 × CO2) conducted with a regional climate model nested in a general circulation model. The regional atmospheric model is the climate version of the National Center for Atmospheric Research/Pennsylvania State University mesoscale model, MM4.Average annual surface temperature of Pyramid Lake for the 2 × CO2 climate is 15.5 ± 5.4°C (±1 σ), 2.8°C higher than the control. Annual overturn of the lake ceases as a result of these higher temperatures for the 2 × CO2 climate. Evaporation increases from 1400 mm yr−1 in the control to 1595 mm yr−1 in the 2 × CO2 simulation, but net water supplied to the Pyramid Lake basin increases from −6 mm yr−1 in the control to +27 mm yr−1 in the 2 × CO2 simulation due to increased precipitation.For the open water periods, the average annual surface temperature of Yellowstone Lake is 13.2 ± 5.1°C for the 2 × CO2 climate, a temperature 1.6°C higher than the control. The annual duration of ice cover on the lake is 152 days in the 2 × CO2 simulation, a reduction of 44 days relative to the control. Warming of the lake for the 2 × CO2 climate is mostly confined to the near-surface. Simulated spring overturn for the 2 × CO2 climate occurs earlier in the year and fall overturn later than in the control. Evaporation increases from 544 mm yr−1 to 600 mm yr−1 in the 2 × CO2 simulation, but net water supplied to the Yellowstone Lake basin increases from +373 mm yr−1 in the control to +619 mm yr−1 due to increased precipitation. The effects of these climatic changes suggest possible deterioration of water quality and productivity in Pyramid Lake and possible enhancement of productivity in Yellowstone Lake. 相似文献
172.
A. V. Uryson 《Astronomy Letters》2018,44(8-9):541-545
The extragalactic sources of ultra-high-energy (E > 4 × 1019 eV) cosmic rays that make a small contribution to the flux of particles recorded by ground-based arrays are discussed. We show that cosmic rays from such sources can produce a noticeable diffuse gamma-ray flux in intergalactic space compared to the the data obtained with Fermi LAT (onboard the Fermi space observatory). A possible type of active galactic nuclei (AGNs) in which cosmi-ray protons can be accelerated to energies 1021 eV is considered as an illustration of such sources. We conclude that ultra-high-energy cosmic rays from the AGNs being discussed can contribute significantly to the extragalactic diffuse gamma-ray emission. In addition, a constraint on the fraction of the AGNs under consideration relative to the BL Lac objects and radio galaxies has been obtained from a comparison with the Fermi LAT data. 相似文献
173.
Graça Cabeçadas M. José Brogueira M. Gelena Cavaco Célia Gonçalves 《Journal of Oceanography》2010,66(2):201-210
Although the circulation of intermediate water masses in the eastern North Atlantic remains poorly defined, the presence of
fresher intermediate waters, the Sub-Artic (SAIW) and the Antarctic Intermediate Water (AAIW), as well the saline intermediate
Mediterranean Water (MW), has been tracked using biogeochemical properties. Here we assess the hydrographic and chemical structures
of intermediate waters along the western Portuguese margin by examining the vertical distributions and property-property plots
of chemical tracers (oxygen and nutrients). AAIW was traced by low oxygen and high nutrients, while SAIW was recognized by
low nutrients. The Mediterranean Water (MW) undercurrent is shown to spread towards the eastern flank of Gorringe bank. Concurrently,
the fresher waters gained salt by direct incorporation of MW, while this water was enriched in nutrients on its way northward
and westward owing, to a great extent, to the entrainment of an AAIW branch. The distributions of nutrients and apparent oxygen
utilization are discussed in terms of regional ocean circulation. Our analysis suggests a circulation pattern of the various
intermediate waters along the western Portuguese margin: MW extends all over the area, but its presence is more pronounced
around cape St. Vincent; SAIW apparently moves southward, reaching the Gorringe bank region, and AAIW flows northward along
the coast and around the bank. 相似文献
174.
Subsidence of organic soils in the Sacramento-San Joaquin Delta threatens sustainability of the California (USA) water supply system and agriculture. Land-surface elevation data were collected to assess present-day subsidence rates and evaluate rice as a land use for subsidence mitigation. To depict Delta-wide present-day rates of subsidence, the previously developed SUBCALC model was refined and calibrated using recent data for CO2 emissions and land-surface elevation changes measured at extensometers. Land-surface elevation change data were evaluated relative to indirect estimates of subsidence and accretion using carbon and nitrogen flux data for rice cultivation. Extensometer and leveling data demonstrate seasonal variations in land-surface elevations associated with groundwater-level fluctuations and inelastic subsidence rates of 0.5–0.8 cm yr–1. Calibration of the SUBCALC model indicated accuracy of ±0.10 cm yr–1 where depth to groundwater, soil organic matter content and temperature are known. Regional estimates of subsidence range from <0.3 to >1.8 cm yr–1. The primary uncertainty is the distribution of soil organic matter content which results in spatial averaging in the mapping of subsidence rates. Analysis of leveling and extensometer data in rice fields resulted in an estimated accretion rate of 0.02–0.8 cm yr–1. These values generally agreed with indirect estimates based on carbon fluxes and nitrogen mineralization, thus preliminarily demonstrating that rice will stop or greatly reduce subsidence. Areas below elevations of –2 m are candidate areas for implementation of mitigation measures such as rice because there is active subsidence occurring at rates greater than 0.4 cm yr–1. 相似文献
175.
A promising method for gas hydrates exploration incorporates pre-stack seismic inversion data, elastic properties modeling, and seismic interpretation to predict saturation of gas hydrates (Sgh). The technology can be modified slightly and used for predicting hydrate concentrations in shallow arctic locations as well. Examples from Gulf of Mexico Walker Ridge (WR) and Green Canyon (GC) protraction areas illustrate how Sgh was derived and used to support the selection of well locations to be drilled for gas hydrates in sand reservoirs by the Chevron-led Joint Industry Project (JIP) Leg II cruise in 2009. Concentrations of hydrates were estimated through the integration of seismic inversion of carefully conditioned pre-stack data, seismic stratigraphic interpretation, and shallow rock property modeling. Rock property trends were established by applying principles of rock physics and shallow sediment compaction, constrained by regional geological knowledge. No nearby sonic or density logs were available to define the elastic property trends in the zone of interest. Sgh volumes were generated by inverting pre-stack data to acoustic and shear impedance (PI and SI) volumes, and then analyzing deviations from modeled impedance trends. In order to enhance the quality of the inversion, we stress the importance of maximizing the signal to noise ratio of the offset data by conditioning seismic angle gathers prior to inversion. Seismic interpretation further plays an important role by identifying false anomalies such as hard, compact strata, which can produce apparent high Sgh values, and by identifying the more promising strata and structures for containing the hydrates. This integrated workflow presents a highly promising methodology, appropriate for the exploration of gas hydrates. 相似文献
176.
New stacked central configurations for the planar 5-body problem 总被引:1,自引:0,他引:1
Jaume Llibre Luis Fernando Mello Ernesto Perez-Chavela 《Celestial Mechanics and Dynamical Astronomy》2011,110(1):43-52
A stacked central configuration in the n-body problem is one that has a proper subset of the n-bodies forming a central configuration. In this paper we study the case where three bodies with masses m
1, m
2, m
3 (bodies 1, 2, 3) form an equilateral central configuration, and the other two with masses m
4, m
5 are symmetric with respect to the mediatrix of the segment joining 1 and 2, and they are above the triangle generated by
{1, 2, 3}. We show the existence and non-existence of this kind of stacked central configurations for the planar 5-body problem. 相似文献
177.
陕西黄土高原人工林土壤干层及形成原因 总被引:1,自引:0,他引:1
1 Introduction Abroad, a lot of research on soil water removal, seeping and evaporation has been done (Ole, 1998; Rapp, 2000). A seeping model of soil water was suggested (Yuin, 1998) and it was known that water removal is very slow in the unsaturated zon… 相似文献
178.
While many studies of non-native species have examined either soft-bottom or hard-bottom marine communities, including artificial structures at docks and marinas, formal comparisons across these habitat types are rare. The number of non-indigenous species (NIS) may differ among habitats, due to differences in species delivery (trade history) and susceptibility to invasions. In this study, we quantitatively compared NIS to native species richness and distribution and examined community similarity across hard-bottom and soft-sediment habitats in San Francisco Bay, California (USA). Benthic invertebrates were sampled using settlement panels (hard-bottom habitats) and sediment grabs (soft-bottom habitats) in 13 paired sites, including eight in higher salinity areas and five in lower salinity areas during 2 years. Mean NIS richness was greatest in hard-bottom habitat at high salinity, being significantly higher than each (a) native species at high salinity and (b) NIS richness at low salinity. In contrast, mean NIS richness in soft-bottom communities was not significantly different from native species richness in either high- or low-salinity waters, nor was there a difference in NIS richness between salinities. For hard-bottom communities, NIS represented an average of 79% of total species richness per sample at high salinity and 78% at low salinity, whereas the comparable values for soft bottom were 46 and 60%, respectively. On average, NIS occurred at a significantly higher frequency (percent of samples) than native species for hard-bottom habitats at both salinities, but this was not the case for soft-bottom habitats. Finally, NIS contributed significantly to the existing community structure (dissimilarity) across habitat types and salinities. Our results show that NIS richness and occurrence frequency is highest in hard-bottom and high-salinity habitat for this Bay but also that NIS contribute strongly to species richness and community structure across each habitat evaluated. 相似文献
179.
O. M. Alifanov A. L. Medvedskiy V. V. Terentyev D. V. Lyskov 《Solar System Research》2018,52(7):590-596
The development project of a prototype demonstrator for a descent vehicle and the possibilities of descent from orbit using aero-elastic braking devices deployable in space and in the atmosphere is considered. The project was carried out jointly by the Lavochkin Scientific Production Association and the Moscow Aviation Institute teams in 2013–2015. The results are evaluated for both the project itself and the cooperation of the two organizations. 相似文献
180.
David W. Hughes 《Earth, Moon, and Planets》1995,68(1-3):311-322
Summary The world's most famous meteor shower picture (Fig. 1) is of the storm that took place in the early morning of Wednesday, 13 November 1833. The picture was, however, produce 54 years after the event, being first published in April 1888. It had a biblical origin and was only taken over by the astronomers in the mid 1920s. The artist was the Swiss painter Karl Jauslin and the engraver was Adolf Völlmy. 相似文献