The eigenvalue equations of equatorial waves on a sphere     

By YAIR DE-LEON  CARYNELISA ERLICK  NATHAN PALDOR 《地球，A辑:动力气象学与海洋学》2010,62(1):62-70

Zonally propagating wave solutions of the linearized shallow water equations (LSWE) in a zonal channel on the rotating spherical earth are constructed from numerical solutions of eigenvalue equations that yield the meridional variation of the waves' amplitudes and the phase speeds of these waves. An approximate Schrödinger equation, whose potential depends on one parameter only, is derived, and this equation yields analytic expressions for the dispersion relations and for the meridional structure of the waves' amplitudes in two asymptotic cases. These analytic solutions validate the accuracy of the numerical solutions of the exact eigenvalue equation. Our results show the existence of Kelvin, Poincaré and Rossby waves that are harmonic for large radius of deformation. For small radius of deformation, the latter two waves vary as Hermite functions. In addition, our results show that the mixed mode of the planar theory (a meridional wavenumber zero mode that behaves as a Rossby wave for large zonal wavenumbers and as a Poincaré wave for small ones) does not exist on a sphere; instead, the first Rossby mode and the first westward propagating Poincaré mode are separated by the anti-Kelvin mode for all values of the zonal wavenumber.  相似文献   

The probability distribution function of the Lyman α transmitted flux from a sample of Sloan Digital Sky Survey quasars     

Vincent Desjacques  Adi Nusser  Ravi K. Sheth 《Monthly notices of the Royal Astronomical Society》2007,374(1):206-219

We present a measurement of the probability distribution function (PDF) of the transmitted flux in the Lyman α (Lyα) forest from a sample of 3492 quasars included in the Sloan Digital Sky Survey data release 3 (SDSS DR3). Our intention is to investigate the sensitivity of the Lyα flux PDF as measured from low-resolution and low signal-to-noise ratio data to a number of systematic errors such as uncertainties in the mean flux, continuum and noise estimate. The quasar continuum is described by the superposition of a power law and emission lines. We perform a power-law continuum fitting on a spectrum-by-spectrum basis, and obtain an average continuum slope of  α_ν= 0.59 ± 0.36  in the redshift range  2.5 < z < 3.5  . We take into account that the variation in the continuum indices increases the mean flux by 3 and 7 per cent at   z = 3  and 2.4, respectively, as compared to the values inferred with a single (mean) continuum slope. We compare our measurements to the PDF obtained with mock lognormal spectra, whose statistical properties have been constrained to match the observed Lyα flux PDF and power spectrum of high-resolution data. Using our power-law continuum fitting and the SDSS pipeline noise estimate yields a poor agreement between the observed and mock PDFs. Allowing for a break in the continuum slope and, more importantly, for residual scatter in the continuum level substantially improves the agreement. A decrease of ∼10–15 per cent in the mean quasar continuum with a typical rms variance at the 20 per cent level can account for the data, provided that the noise excess correction is no larger than ≲10 per cent.  相似文献   

Estimating of gas transfer velocity using triple isotopes of dissolved oxygen     

V. V. S. S. Sarma  Osamu Abe  Makio Honda  Toshiro Saino 《Journal of Oceanography》2010,66(4):505-512

The atmosphere-ocean exchange of climatically important gases is determined by the transfer velocity (k) and concentration gradient across the interface. Based on observations in the northwestern subarctic Pacific and Sagami Bay, we report here the results of the first ever application of the natural abundance of triple isotopes of dissolved oxygen (¹⁶O, ¹⁷O and ¹⁸O) for direct estimation of k and propose a new relationship with wind speed. The k values estimated from nighttime variations in oxygen isotopes are found to be higher than the direct estimations at low wind speed (<5 m s⁻¹) and lower at high wind speeds (>13 m s⁻¹) and showed significant spatial variability. The method presented here can be used to derive seasonal and spatial variations in k and the influence of surface conditions on the value, leading to improved estimates of biogenic/anthropogenic gas exchange at the air-sea interface.  相似文献   

Limnological instrumentation in the middle of the 19th century: the first temperature and density profiles measured in the Dead Sea     

Aharon Oren 《中国海洋湖沼学报》2015,33(6):1496-1504

The first modern survey of the Dead Sea was performed by the Geological Survey of Israel in 1959–1960,and the report published remains the baseline study for our understanding of the physical and chemical properties of the lake.At the time the Dead Sea was a meromictic lake with a strong salinity gradient separating the deep waters(40 m depth) from the less saline surface waters.A few results of analyses of deeper water samples collected in the 1930 s were reported,but overall we have very little information about the structure of the lake's water column before the 1959–1960 survey.However,it is little known that data on the physical and the chemical structure of the Dead Sea water column were obtained already in the middle of the 19 th century,and the information collected then is highly relevant for the reconstruction of the limnological properties of the lake in earlier times.The expedition of Lieutenant William Lynch(U.S.Navy) in 1848 reported the presence of a temperature minimum at a depth of ~18 m,and also retrieved a water sample collected close to the bottom for chemical analysis.In 1864,the French Dead Sea exploration by the Duc de Luynes and his crew yielded detailed density and salinity profiles for a number of sampling stations.The results of these pioneering studies are discussed here,as well as the sampling equipment and measuring instruments used by the 1848 and the 1864 expeditions.  相似文献   

Passive dew collection in a grassland area, The Netherlands   总被引：1，自引：1，他引：0  

A.F.G. Jacobs  B.G. Heusinkveld  S.M. Berkowicz 《Atmospheric Research》2008,87(3-4):377

Passive dew collection experiments were initiated in late 2003 in the centre of The Netherlands within a grassland area. A specially designed 1 m² insulated planar dew collector, set at a 30° angle from horizontal, was covered with a thin (0.39 mm) polyethylene foil and subsequently replaced with 4 mm polyvinyl chloride. A second dew collector, in the shape of an inverted pyramid, was constructed to reduce the view angle to only the nighttime sky. A simple surface energy-budget model and an aerodynamic model were used to simulate the dew collected by both collectors. The planar collector collected about 90% of the dew at the grass cover while the pyramid collector collected about 1.20% of the grass cover. The aerodynamic model was able to predict the amount of collector data to within 50% for the planar collector and 60% for the inverted pyramid collector. The pyramid collector design was able to collect about 20% more dew than the inclined planar collector.  相似文献   

Abrasion-derived sediments under intensified winds at the latest Pleistocene leading edge of the advancing Sinai-Negev erg     

Yehouda Enzel  Rivka Amit  Onn Crouvi  Naomi Porat 《Quaternary Research》2010,74(1):121-482

Quaternary desert loess and sandstone-loessite relationships in the geological record raise questions regarding causes and mechanisms of silt formation and accretion. In the northern Sinai-Negev desert carbonate terrain, only sand abrasion in active erg could have produced the large quantities of quartzo-feldspathic silts constituting the late Quaternary northwestern Negev loess. In the continuum of source (medium to fine sand of dunes) to sink (silts in loess) the very fine sand is unaccounted for in the record. This weakens the sand abrasion model of silt formation as a global process. Here, we demonstrate that, as predicted by experiments, abrasion by advancing dunes generated large quantities of very fine sand (60-110 μm) deposited within the dune field and in close proximity downwind. This very fine sand was generated 13-11 ka, possibly synchronous with the Younger Dryas under gusty sand/dust storms in the southeastern Mediterranean and specifically in the northern Sinai-Negev erg. These very fine sands were washed down slope and filled small basins blocked by the advancing dunes; outside these sampling basins it is difficult to identify these sands as a distinct product. We conclude that ergs are mega-grinders of sand into very fine sand and silt under windy Quaternary and ancient aeolian desert environments.  相似文献   

Variation in abundance and distribution of diamondoids during oil cracking     

《Organic Geochemistry》2012

In this study, changes in the abundance and distribution of diamondoids in petroleum with thermal maturity were investigated by a simulation oil cracking experiment. Highly sensitive and selective gas chromatography–triple quadrupole mass spectrometry (GC–MS–MS) was employed to quantify diamondoids at ppm and sub-ppm levels. The results indicate that diamondoids were generated primarily within the maturity range 1.0–2.1% EasyRo and destroyed at high thermal maturity (>2.1% EasyRo). Hence, the occurrence of high concentrations of diamondoids probably corresponds to the maturity range from the wet gas to the early dry gas stage (i.e., 1.5–2.5% EasyRo). Good correlations were observed between a few ratios of diamondoids (i.e., EAI, DMAI-1, DMDI-1 and TMAI-1) and EasyRo. This finding indicates that these parameters may be useful maturity indices for organic matter from the late oil window to the dry gas window.  相似文献   

Characterization of the halophilic archaeal community in saltern crystallizer ponds by means of polar lipid analysis   总被引：1，自引：0，他引：1  

Aharon Oren 《International Journal of Salt Lake Research》1994,3(1):15-29

Saltern crystallizer ponds are coloured red due to the presence of dense communities of red halophilic archaea (family Halobacteriaceae). Little quantitative information exists on the species distribution within the archaeal community in such ponds. As the different genera of the Halobacteriaceae differ in polar lipid content, and especially in the types of glycolipids, lipid analysis can be used to obtain information on the nature of the organisms present. Analysis of the polar lipids extracted from the biomass collected from the saltern crystallizer ponds in Eilat, Israel, showed one major glycolipid to be present, co-chromatographing with the sulfated diglycosyl diether lipid characteristic of the genusHaloferax. No indications were found for the presence of significant amounts of those glycolipids that would indicate the presence of large numbers of other archaea such asHalobacterium species (H. cutirubrum andH. salinarium, characterized by sulfated triglycosyl and tetraglycosyl diethers), orHaloarcula species (possessing a triglycosyl diether). Phosphatidyl glycerosulfate, a polar lipid absent inHaloferax species, was present in the lipid extract from the crystallizer ponds, suggesting that the dominant microorganism present may be related to strains which are presently classified in the genusHalobacterium but are awaiting a taxonomic reappraisal (H. sodomense, H. saccharovorum, andH. trapanicum). Organisms of the latter group are characterized by sulfated diglycosyl diethers, and the presence of phosphatidyl glycerosulfate. Attempts to isolate the dominant type of bacterium on agar plates yielded relatively low counts (1–2 orders of magnitude lower than the numbers observed microscopically) of bacteria, and most of the isolates had a polar lipid composition characteristic of theH. salinarium group or theH. sodomense-H. saccharovorum-H. trapanicum group.  相似文献   

P-T conditions of quartz-calcite boudins and vein formation within a low-angle detachment fault in Tinos Island (Aegean Sea): a fluid-inclusion study     

Ye.?VapnikEmail author  D.?Avigad 《International Journal of Earth Sciences》2004,93(4):487-499

Fluid inclusions were investigated in successive generations of quartz-calcite boudins and veins in the vicinity of, and within, the low-angle detachment fault (of Early Miocene age) exposed on Tinos Island (Cyclades, Greece). Abundant boudins, veins, tension gashes and mineral segregations were formed during various stages of ductile and brittle shear along the detachment indicating fluid flow at various crustal levels, assisted motion and slip along the detachment. Three generations of fluid inclusions were identified: (1) syn-deformation aqueous inclusions; (2) local- late-deformation H₂O-CO₂ inclusions; (3) post-slip deformation, partly decrepitated aqueous and H₂O-CO₂ inclusions. The conditions of inclusion trapping correspond to the greenschist facies, at temperatures between 300 and 450°C and pressures in the range of 1.5–4.0 kb. A gradient of pressure of about 0.5 kb from the fault zone to the rocks of upper and lower plates is suggested. The results indicate that the syn-deformation fluid was NaCl-KCl-sulfate-dominated with a salinity of about 5 wt% NaCl equiv. Downward infiltration of meteoric water is a suitable source for this fluid. During the late stage of fault activity, in the brittle field, fluid was of H₂O-CO₂ composition. Very rapid exhumation of the entire section (unrelated to motion on the investigated fault) is marked by numerous decrepitation clusters of the fluid inclusions.  相似文献   

Mechanisms of sulfur introduction chemically controlled: δS imprint     

Alon Amrani  Zeev Aizenshtat   《Organic Geochemistry》2004,35(11-12):1319

Organic sulfur in marine sediment is ³⁴S enriched relative to the co-existing pyrite. This phenomenon is still enigmatic. Timing of the sulfur incorporation, immobilization and different sulfur species involved are part of the explanations. The reduced sulfur species incorporation into organic matter (OM) is generally assumed to have negligible δ³⁴S fractionation. This assumption has never been confirmed by laboratory experimental data. The present study measures the δ³⁴S changes resulting from reduced sulfur species (sulfides and polysulfide anions) incorporation into organic model compounds in an aquatic and low temperature (25 °C) system that simulates diagenetic marine environment. In addition, we also investigate the δ³⁴S fractionation and the isotope chemical mixing in the formation of polysulfide anions produced from elemental sulfur and sulfide anions. The results showed total isotope mixing between the two species in the formation of polysulfides. Acidification of the polysulfides solution caused δ³⁴S fractionation between the released elemental sulfur and H₂S. The incorporation of polysulfides and sulfides into carbonyl groups, caused ³⁴S enrichment relative to the starting polysulfides and sulfide of 4–5‰. The ³⁴S enrichment of the sulfurized carbonyl groups showed a minimal effect by temperature (0–70 °C) and is not affected by salinity, polysulfides composition, reaction time or solubility in water. The incorporation of polysulfides and sulfides into brominated organic compounds was negligibly ³⁴S enriched. The chemical mechanisms controlling the polysulfides incorporation into OM depend mostly on the functional groups and determine the ³⁴S enrichment of the sulfurized OM. The results presented in this study can explain part of the difference between pyrite δ³⁴S and sulfurized OM δ³⁴S in natural marine sediments.  相似文献