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1.
Features of atmospheric circulation and thermal structures are discussed using the NCAR/NCEP
data to reveal the reasons for the late onset and anomalous southward persistence of the South China Sea
Summer Monsoon (SCSSM) in 2005. The results show that three factors are crucial. First, a strong
Arabian High overlaps with a high-latitude blocking high and channels strong cold air to southern Asia.
Second, the Tibetan Plateau has a bigger snow cover than usual in spring and the melting of snow cools
down the surface. Third, the Somali Jet breaks out at a much later date, being not conducive to convection
over Indochina. The former two factors restrict atmospheric sensible heating over the Tibetan Plateau and
nearby regions while the third one limits latent heating over Indochina. All of the factors slow down
atmospheric warming and postpone the onset of SCSSM. Long after the onset of SCSSM, strong cold air
over India advances the Southwest Monsoon northward slowly, resulting in weaker convection and latent
heating over the Tibetan Plateau and nearby areas. The negative feedback conversely inhibits further
northward movement of Southwest Monsoon. 相似文献
2.
Ricardo Castelló Clemente Recio Pilar Morillas Carmen Vizcayno 《Environmental Geology》2008,54(4):679-688
The role of municipal solid waste (MSW) landfill leachate on the genesis of minor amounts of pyrite associated with gypsum
in an otherwise predominantly evaporitic sequence was studied in geological and geochemical terms. The potential association
between landfill leachate and the conditions required for bacterial reduction of sulfate and fixation of H2S as pyrite were examined. The lithological column was generally found to contain little or no Fe. The δ34S values for sulfates were consistent with previously reported data; however, the measured δ18O values were slightly higher. Sulfides disseminated in the marl/lutite exhibited higher δ34S values (≈−8‰) than gypsum-coating pyrite crystals (δ34S < −30‰). Dissolution of gypsum to sulfate and the supply of metabolizable organic matter and Fe required for H2S fixation as sulfides may have originated from landfill leachate. Intermittent availability of leachate, a result of the
precipitation regime, can facilitate sulfur disproportionation and lead to fractionations as high as 相似文献
3.
Results of an experimental study of the oxidation of a zirconium plasma generated by laser ablation of a metallic target under low pressures of oxygen are presented. The crystallographic identification of the collected product by electronic diffraction shows metastable ZrO cubic phase. The oxidation phenomena are interpreted by thermochemical simulation suggesting a model in accordance with other cases of synthesis of metastable oxides at high temperatures, such as plasma reactors. 相似文献
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Nuria Castell Ariel F. Stein Enrique Mantilla Rosa Salvador Millán Millán 《Journal of Atmospheric Chemistry》2009,63(1):73-91
Understanding the chemical links between ozone (O3) and its two main precursors, nitrogen oxides (NOx) and volatile organic compounds (VOC), is important for designing effective
photochemical smog reduction strategies. This chemical relationship will determine which precursor (NOx or VOC) emission reduction
will be more effective for decreasing the ozone formation. Under certain conditions, ozone levels decrease as a result of
a reduction in NOx emissions but do not respond significantly to changes in VOC emissions (NOx-sensitive condition), while
under other conditions ozone concentrations decrease in response to reductions in VOCs and may even increase when NOx emissions
are reduced (VOC-sensitive conditions). Indicator species can be used to assess the sensitivity of ozone to changes in the
emissions of its precursors. These indicators are species or species ratios involved in ozone photochemistry which reflect
the primary chemical process through which the ozone was formed. In this work we use the MM5-CAMx model system to explore
the behaviour of various indicator species during two meteorological situations featuring different atmospheric conditions
in a complex terrain area. The results show that indicators based on nitrogen compounds (i.e,. NOy and NOz) are suitable for
defining the transition range from VOC- to NOx-sensitive chemistry, and that despite the uncertainties associated with the
use of chemical indicators, the ratios O3/NOy and O3/NOz may provide a simple and useful way to summarize the response of ozone to changes in NOx and VOC emissions in Southwestern
Spain. 相似文献
6.
Optical emission studies have been performed on the laser ablation of Titanium metallic targets. The high intensity radiation of a pulsed N2 laser (337.1 nm; 8 J/cm2) was focused onto the target to generate a short living (150 ns) plasma cloud that expands away from the surface into vacuum at high velocities. Time resolved measurements were taken as a function of the distance from the studied surface with a spatial rsolution of 20 µm, by collecting the emitted light in a direction perpendicular to the plasma expansion axis. A simple diffusion model with a source term is proposed to demonstrate the interaction of the laser beam with the plasma plume, as derived from analysis of the space-time behavior of several UV and visible atomic transitions. 相似文献
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8.
André M van der Schaar M Zaugg S Houégnigan L Sánchez AM Castell JV 《Marine pollution bulletin》2011,63(1-4):18-26
The development and broad use of passive acoustic monitoring techniques have the potential to help assessing the large-scale influence of artificial noise on marine organisms and ecosystems. Deep-sea observatories have the potential to play a key role in understanding these recent acoustic changes. LIDO (Listening to the Deep Ocean Environment) is an international project that is allowing the real-time long-term monitoring of marine ambient noise as well as marine mammal sounds at cabled and standalone observatories. Here, we present the overall development of the project and the use of passive acoustic monitoring (PAM) techniques to provide the scientific community with real-time data at large spatial and temporal scales. Special attention is given to the extraction and identification of high frequency cetacean echolocation signals given the relevance of detecting target species, e.g. beaked whales, in mitigation processes, e.g. during military exercises. 相似文献
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This paper focuses on some aspects of the motion of a small particle moving near the Lagrangian points of the Earth–Moon system.
The model for the motion of the particle is the so-called bicircular problem (BCP), that includes the effect of Earth and
Moon as in the spatial restricted three body problem (RTBP), plus the effect of the Sun as a periodic time-dependent perturbation
of the RTBP. Due to this periodic forcing coming from the Sun, the Lagrangian points are no longer equilibrium solutions for
the BCP. On the other hand, the BCP has three periodic orbits (with the same period as the forcing) that can be seen as the
dynamical equivalent of the Lagrangian points. In this work, we first discuss some numerical methods for the accurate computation
of quasi-periodic solutions, and then we apply them to the BCP to obtain families of 2-D tori in an extended neighbourhood
of the Lagrangian points. These families start on the three periodic orbits mentioned above and they are continued in the
vertical (z and ż) direction up to a high distance. These (Cantor) families can be seen as the continuation, into the BCP, of the Lyapunov
family of periodic orbits of the Lagrangian points that goes in the (z, ż) direction. These results are used in a forthcoming work [9] to find regions where trajectories remain confined for a
very long time. It is remarkable that these regions seem to persist in the real system.
This revised version was published online in July 2006 with corrections to the Cover Date. 相似文献