A new approach to develop the Raman carbonaceous material geothermometer for low‐grade metamorphism using peak width     

Yui Kouketsu  Tomoyuki Mizukami  Hiroshi Mori  Shunsuke Endo  Mutsuki Aoya  Hidetoshi Hara  Daisuke Nakamura  Simon Wallis 《Island Arc》2014,23(1):33-50

The Raman spectra of carbonaceous material (CM) from 19 metasediment samples collected from six widely separated areas of Southwest Japan and metamorphosed at temperatures from 165 to 655°C show systematic changes with metamorphic temperature that can be classified into four types: low‐grade CM (c. 150–280°C), medium‐grade CM (c. 280–400°C), high‐grade CM (c. 400–650°C), and well‐crystallized graphite (> c. 650°C). The Raman spectra of low‐grade CM exhibit features typical of amorphous carbon, in which several disordered bands (D‐band) appear in the first‐order region. In the Raman spectra of medium‐grade CM, the graphite band (G‐band) can be recognized and several abrupt changes occur in the trends for several band parameters. The observed changes indicate that CM starts to transform from amorphous carbon to crystallized graphite at around 280°C, and this transformation continues until 400°C. The G‐band becomes the most prominent peak at high‐grade CM suggesting that the CM structure is close to that of well‐crystallized graphite. In the highest temperature sample of 655°C, the Raman spectra of CM show a strong G‐band with almost no recognizable D‐band, implying the CM grain is well‐crystallized graphite. In the Raman spectra of low‐ to medium‐grade CM, comparisons of several band parameters with the known metamorphic temperature show inverse correlations between metamorphic temperature and the full width at half maximum (FWHM) of the D1‐ and D2‐bands. These correlations are calibrated as new Raman CM geothermometers, applicable in the range of c. 150–400°C. Details of the methodology for peak decomposition of Raman spectra from the low to medium temperature range are also discussed with the aim of establishing a robust and user‐friendly geothermometer.  相似文献   

Fourier transform infrared microspectroscopic characterization of Neoproterozoic organic microfossils from the Fifteenmile Group in Yukon,Canada     

Motoko Igisu  Tsuyoshi Komiya  Stanley M. Awramik  Yuka Ikemoto  Yechuan Geng  Hiroki Uehara  Ken Takai 《Island Arc》2019,28(5)

Conventional and synchrotron radiation‐based (SR) Fourier transform infrared microspectroscopies (micro‐FTIR) were applied to four types of ~ 810 Ma organic‐walled microfossils together with diffuse organic matter (OM) and one irregularly shaped structure from the Fifteenmile Group, in Yukon, Canada, for their chemical characterization. The microfossils comprised one filamentous type and three coccoidal types. Micro‐FTIR mapping analysis revealed the micrometer‐scale, spatial distribution of organic components (aliphatic C‐H bonds) and carbonate in the microfossils. Based on comparisons of CH₃/CH₂ peak height ratios (R_3/2) and morphologies of the microfossils (without the diffuse OM) to those of previously described Proterozoic microfossils, possible affinities of the microfossils are suggested, as follows. Palaeolyngbya? and Glenobotrydion belong to bacteria. Myxococcoides is not clearly characterized due to the significant mixing with diffuse OM containing abundant aliphatic C‐H groups. The irregularly shaped structure may represent a eukaryote. The diffuse OM may represent a mixture of decomposed microbial cells and extracellular polymeric substances (EPS). SR micro‐FTIR measurements of two coccoid types (Glenobotrydion and Unnamed Coccoid Form D) revealed that the R_3/2 values of the internal spots with wall structures are similar to those without wall structures in Glenobotrydion: those values from Unnamed Coccoid Form D were different. The results suggest that these two coccoids are different chemically as well as morphologically. Micro‐FTIR characterization of the organic‐walled microfossils together with morphological analysis provides new insight into their biological affinities.  相似文献   

Rock physics analysis for time-lapse seismic at Schiehallion Field, North Sea   总被引：1，自引：0，他引：1  

Mark Meadows  Don Adams  Rich Wright †  Ali Tura  Steve Cole  David Lumley 《Geophysical Prospecting》2005,53(2):205-213

Rock physics analysis plays a vital role in time‐lapse seismic interpretation because it provides the link between changes in rock and fluid properties and the resulting seismic data response. In this case study of the Schiehallion Field, we discuss a number of issues that commonly arise in rock physics analyses for time‐lapse studies. We show that:

• 1 Logarithmic fits of dry bulk (K_dry) and shear (G_dry) moduli vs. effective pressure (P_eff) are superior to polynomial fits.
• 2 2D surface fits of K_dry and G_dry over porosity (φ) and effective pressure using all the core data simultaneously are more useful and accurate than separate 1D fits over φ and P_eff for each individual core.
• 3 One average set (facies) of K_dry(φ, P_eff) and G_dry(φ, P_eff) can be chosen to represent adequately the entire Schiehallion reservoir.
• 4 Saturated velocities and densities modelled by fluid substitution of K_dry(φ, P_eff), G_dry(φ, P_eff) and the dry bulk density ρ_dry(φ) compare favourably with well‐log velocities and densities.
• 5 P‐ and S‐wave impedance values resulting from fluid substitution of K_dry(φ, P_eff), G_dry(φ, P_eff) and ρ_dry(φ) show that the largest impedance changes occur for high porosities and low effective pressures.
• 6 Uncertainties in K_dry(φ, P_eff) and G_dry(φ, P_eff) derived for individual cores can be used to generate error surfaces for these moduli that represent bounds for quantifying uncertainties in seismic modelling or pressure–saturation inversion.

  相似文献   

Performance of A Combination Process of UV/H2O2/Micro‐Aeration for Oxidation of Dichloroacetic Acid in Drinking Water     

WenHai Chu  N. Y. Gao  Y. Deng 《洁净——土壤、空气、水》2009,37(3):233-238

The decomposition of dichloroacetic acid (DCAA) in water using a UV/H₂O₂/micro‐aeration process was investigated in this paper. DCAA cannot be removed by UV radiation, H₂O₂ oxidation or micro‐aeration alone, while UV/H₂O₂/micro‐aeration combination processes have proved effective and can degrade this compound completely. With initial concentrations of about 110 μg/L, more than 95.1% of DCAA can be removed in 180 min under UV intensity of 1048.7 μW/cm², H₂O₂ dosage of 30 mg/L and micro‐aeration flow rate of 2 L/min. However, more than 30 μg/L of DCAA was left after 180 min by UV/H₂O₂ combination process without micro‐aeration with the same UV intensity and H₂O₂ dosage. The effects of applied UV radiation intensity, H₂O₂ dose, initial DCAA concentration and pH on the degradation of DCAA have been examined in this study. Degradation mechanisms of DCAA with hydroxyl radical oxidation have been discussed. The removal rate of DCAA was sensitive to operational parameters. There was a linear relationship between rate constant k and UV intensity and initial H₂O₂ concentration, which indicated that a higher removal capacity can be achieved by improvement of both factors. A newly found nitrogenous disinfection by‐product (N‐DBP)‐DCAcAm, which has the potential to form DCAA, was easier to remove than DCAA by UV/H₂O₂ and UV/H₂O₂/micro‐aeration processes. Finally, a preliminary cost comparison revealed that the UV/H₂O₂/micro‐aeration process was more cost‐effective than the UV/H₂O₂ process in the removal of DCAA from drinking water.  相似文献   

Characterization of Estuarine and Fluvial Dissolved Organic Matter by Thermochemolysis using Tetramethylammonium Hydroxide     

J. D. H. van Heemst  J. C. del Rio  P. G. Hatcher  J. W. de Leeuw 《洁净——土壤、空气、水》2000,28(2):69-76

Selected samples of dissolved organic matter (DOM) isolated by ultrafiltration (UDOM) have been analyzed by thermochemolysis in the presence of tetramethylammonium hydroxide (TMAH). This technique cleaves ester and ether bonds of bio‐ and geological macromolecules and releases monomer subunits and methylates them in situ as their methyl ethers and methyl esters. Compared with conventional pyrolysis, TMAH thermochemolysis avoids decarboxylation of preexisting carboxylic moieties and produces aromatic acids as their methyl esters. Various phenolic derivatives, which might originate from incorporated lignin‐derived structures, from the highly aliphatic and resistant biopolymer cutan and also from proteinaceous materials, were identified among the products produced from UDOM upon thermochemolysis. The presence of lignin derivatives in UDOM indicates input of organic matter derived from terrestrial sources. Various aromatic acids, perhaps representing the final steps in the oxidation of the side‐chain during microbial oxidation of lignin, were released upon TMAH thermochemolysis, suggesting they are structural constituents of the UDOM. Different ratios of lignin‐derived materials, commonly determined using the CuO oxidation method, such as the Δ value, indicative of the amount of lignin present, the acid/aldehyde ratio (Ad/Al)_G, indicative of the extent of oxidative degradation of the lignin component, and the syringyl/guaiacyl (S/G) and p‐hydroxyphenyl/guaiacyl (P/G) ratios, indicative of the contribution for the different types of lignin, were determined.  相似文献   

A new occurrence of retrogressed eclogite from the Sanbagawa belt of southwest Japan and its significance     

Tomoki Taguchi  Shunsuke Endo  Yohei Igami  Akira Miyake 《Island Arc》2019,28(5)

The present paper reports, for the first time, the occurrence of an omphacite‐bearing mafic schist from the Asemi‐gawa region of the Sanbagawa belt (southwest Japan). The mafic schist occurs as thin layers within pelitic schist of the albite–biotite zone. Omphacite in the mafic schist only occurs as inclusions in garnet, and albite is the major Na phase in the matrix, suggesting that the mafic schist represents highly retrogressed eclogite. Garnet grains in the sample show prograde‐type compositional zoning with no textural or compositional break, and contain mineral inclusions of omphacite, quartz, glaucophane, barroisite/hornblende, epidote and titanite. In addition to the petrographic observations, Raman spectroscopy and focused ion beam system–transmission electron microscope analyses were used for identification of omphacite in the sample. The omphacite in the sample shows a strong Raman peak at 678 cm^?1, and concomitant Raman peaks are all consistent with those of the reference omphacite Raman spectrum. The selected area electron diffraction pattern of the omphacite is compatible with the common P2/n omphacite structure. Quartz inclusions in the mafic schist preserve high residual pressure values of Δω₁ > 8.5 cm^?1, corresponding to the eclogite facies conditions. The combination of Raman geothermobarometries and garnet–clinopyroxene geothermometry gives peak pressure–temperature (P–T) conditions of 1.7–2.0 GPa and 440–540 °C for the mafic schist. The peak P–T values are comparable to those of the schistose eclogitic rocks in other Sanbagawa eclogite units of Shikoku. These findings along with previous age constraints suggest that most of the Sanbagawa schistose eclogites and associated metasedimentary rocks share similar simple P–T histories along the Late Cretaceous subduction zone.  相似文献   

Measurement of evapotranspiration in a winter wheat field     

Yongqiang Zhang  Changming Liu  Yanjun Shen  A. Kondoh  Changyuan Tang  T. Tanaka  J. Shimada 《水文研究》2002,16(14):2805-2817

Daily evapotranspiration from a winter wheat field on the North China Plain measured by large‐scale weighing lysimeter was linearly related to that measured by the Bowen ratio energy balance (BREB) technique. Soil evaporation averaged about 23·6% of evapotranspiration from the post‐winter dormancy revival stage to the grain ripening stage in 1999. On clear days during winter dormancy, about half of the net radiation flux R_n was used to warm soil. During the revival stage, conductive heat flux G also used most of the incoming R_n, but the ratio of latent heat flux λE to R_n increased. During the stem‐extension stage, λE was about 50% of R_n; thereafter, λE/R_n increased continually, but G remained less than 10% of R_n. During the ripening stage, λE was almost 90% of R_n. Evaporative fraction (EF) can be expressed as a function of plant status and atmospheric boundary layer conditions. The relationship between EF and available energy under moderate air temperature and vapour pressure deficit conditions was examined for five combinations of aerodynamic and canopy conductance. Although the theoretical relationship indicates that EF should be highly correlated to soil water content, the correlation has been difficult to identify under field conditions. However, we observed that there exists a threshold value of R_n ? G, above which EF is less than 1·0, and that the threshold value is lower under soil‐water deficit conditions than under abundant soil‐water conditions. Copyright © 2002 John Wiley & Sons, Ltd.  相似文献   

Classification of hydrological regimes of northern floodplain basins (Peace–Athabasca Delta,Canada) from analysis of stable isotopes (δ18O, δ2H) and water chemistry     

Brent B. Wolfe  Tammy L. Karst‐Riddoch  Roland I. Hall  Thomas W. D. Edwards  Michael C. English  Roger Palmini  Suzanne McGowan  Peter R. Leavitt  Sheila R. Vardy 《水文研究》2007,21(2):151-168

We used stable isotopes (δ¹⁸O and δ²H) and water chemistry to characterize the water balance and hydrolimnological relationships of 57 shallow aquatic basins in the Peace‐Athabasca Delta (PAD), northern Alberta, Canada, based on sampling at the end of the 2000 thaw season. Evaporation‐to‐inflow ratios (E/I) were estimated using an isotope mass‐balance model tailored to accommodate basin‐specific input water compositions, which provided an effective, first‐order, quantitative framework for identifying water balances and associated limnological characteristics spanning three main, previously identified drainage types. Open‐drainage basins (E/I < 0·4; n = 5), characterized by low alkalinity, low concentrations of nitrogen, dissolved organic carbon (DOC) and ions, and high minerogenic turbidity, include large, shallow basins that dominate the interior of the PAD and experience frequent or continuous river channel connection. Closed‐drainage basins (E/I ≥ 1·0; n = 16), in contrast, possess high alkalinity and high concentrations of nitrogen, DOC, and ions, and low minerogenic turbidity, and are located primarily in the relict and infrequently flooded landscape of the northern Peace sector of the delta. Several basins fall into the restricted‐drainage category (0·4 # E/I < 1·0; n = 26) with intermediate water chemistries and are predominant in the southern Athabasca sector, which is subject to active fluviodeltaic processes, including intermittent flooding from riverbank overflow. Integration of isotopic and limnological data also revealed evidence for a new fourth drainage type, mainly located near the large open‐drainage lakes that occupy the central portion of the delta but within the Athabasca sector (n = 10). These basins were very shallow (<50 cm deep) at the time of sampling and isotopically depleted, corresponding to E/I characteristic of restricted‐ and open‐drainage conditions. However, they are limnologically similar to closed‐drainage basins except for higher conductivity and higher concentrations of Ca²⁺ and Na⁺, and lower concentrations of SiO₂ and chlorophyll c. These distinct features are due to the overriding influence of recent summer rainfall on the basin water balance and chemistry. The close relationships evident between water balances and limnological conditions suggest that past and future changes in hydrology are likely to be coupled with marked alterations in water chemistry and, hence, the ecology of aquatic environments in the PAD. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

S‐Doped Magnetic Mesoporous Carbon for Efficient Adsorption of Methyl Orange from Aqueous Solution     

Jiangyan Xu  Shiman Zhai  Bo Zhu  Jingxin Liu  Aimin Lu  Hongmei Jiang 《洁净——土壤、空气、水》2021,49(1)

A simple and rapid soft‐templating coupled with one‐pot solvent thermal method is developed to synthesize S‐doped magnetic mesoporous carbon (S‐doped MMC). In this method, phenolic resin is used as a carbon precursor and Pluronic copolymer P123 is used as a template and 2,5‐dimercapto‐1,3,4‐thiadiazole is used as sulfur source. Prepared S‐doped MMC processes a high specific surface area, the Fe₃O₄ particles are well embedded in the mesoporous carbon walls that exhibit a strong magnetic response, and the hydrated iron nitrate loading amount of 0.808 g is the best. Batch adsorption experiments are carried out at different pH, initial concentration, temperature, and contact time on the adsorption of methyl orange (MO) by S‐doped MMC. The kinetic data of the adsorption process are better fitted with pseudo‐second‐order model than the pseudo‐first‐order model. Langmuir model is more suitable for the equilibrium data than Freundlich model. The thermodynamic parameters including ΔG⁰, ΔH⁰, and ΔS⁰ indicate that the adsorption is a feasible, spontaneous, and endothermic process. Finally, it is found that the coexistence of PO₄^3?, NO₃^?, SO₄^2?, Cl^?, and CO₃^2? does not influence the adsorption process. These results illustrate S‐doped MMC can be an efficient adsorbent for the removal of MO from wastewater.  相似文献   

Exchangeable Characteristics of Potassium in Five Important Soils of Taiwan     

Yong‐Hong Lin 《洁净——土壤、空气、水》2010,38(12):1111-1115

The application of potassium fertilizer by farmers is often not appropriate and causing environmental pollution. By understanding the adsorptive characteristics of potassium (K) on different soils, we can prevent excessive application of K‐fertilizer that can cause environmental impact. The Gapon exchange coefficient (K_G), for exchange between K and Ca, was considered as an important factor influencing the adsorption of K. This study was conducted to compare the constant K_G of five important farm soils in Taiwan. The K_G and CEC were then used to predict K buffering capacity (PBC). Finally, the relationship between exchangeable K ratio (E_P) and K adsorption ratio (PAR) was examined. The results show that five soils have same trends, indicating that K_G decreases with increase in K saturation. The CEC and K_G of Liuying (Ly) soil are both high, so that their K buffering capacity is high. The K_G and CEC of Chanjing (Cj) and Sanhua (Sh) soil show moderate values. The CEC of Erling (El) soil is high, but its K_G is low, so that its K buffering capacity is moderate. On the other hand, the K_G of Newniaokang (Nnk) soil is high but its CEC is low, so its K buffering capacity is also moderate. The correlations between E_P and PAR of five soil show linear relationship at three treatments of CaCl₂ concentration. This study may provide an important clue to the fertilization management of K‐fertilizer on the different soil properties in Taiwan.  相似文献   

A bed‐load transport model for rough turbulent open‐channel flows on plane beds     

Athol D. Abrahams  Peng Gao 《地球表面变化过程与地形》2006,31(7):910-928

Data from flume studies are used to develop a model for predicting bed‐load transport rates in rough turbulent two‐dimensional open‐channel flows moving well sorted non‐cohesive sediments over plane mobile beds. The object is not to predict transport rates in natural channel flows but rather to provide a standard against which measured bed‐load transport rates influenced by factors such as bed forms, bed armouring, or limited sediment availability may be compared in order to assess the impact of these factors on bed‐load transport rates. The model is based on a revised version of Bagnold's basic energy equation i_bs_b = e_bω, where i_b is the immersed bed‐load transport rate, ω is flow power per unit area, e_b is the efficiency coefficient, and s_b is the stress coefficient defined as the ratio of the tangential bed shear stress caused by grain collisions and fluid drag to the immersed weight of the bed load. Expressions are developed for s_b and e_b in terms of G, a normalized measure of sediment transport stage, and these expressions are substituted into the revised energy equation to obtain the bed‐load transport equation i_b = ω G ^3·4. This equation applies regardless of the mode of bed‐load transport (i.e. saltation or sheet flow) and reduces to i_b = ω where G approaches 1 in the sheet‐flow regime. That i_b = ω does not mean that all the available power is dissipated in transporting the bed load. Rather, it reflects the fact that i_b is a transport rate that must be multiplied by s_b to become a work rate before it can be compared with ω. It follows that the proportion of ω that is dissipated in the transport of bed load is i_bs_b/ω, which is approximately 0·6 when i_b = ω. It is suggested that this remarkably high transport efficiency is achieved in sheet flow (1) because the ratio of grain‐to‐grain to grain‐to‐bed collisions increases with bed shear stress, and (2) because on average much more momentum is lost in a grain‐to‐bed collision than in a grain‐to‐grain one. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献   

Predicting the onset of thermal stratification in shallow inland waterbodies   总被引：1，自引：0，他引：1  

Brett F. Branco  Thomas Torgersen 《Aquatic Sciences - Research Across Boundaries》2009,71(1):65-79

  相似文献   

Quantifying relations between surface runoff and aridity after wildfire          下载免费PDF全文

René E. Van der Sant  Petter Nyman  Philip J. Noske  Christoph Langhans  Patrick N.J. Lane  Gary J. Sheridan 《地球表面变化过程与地形》2018,43(10):2033-2044

Post‐wildfire runoff and erosion are major concerns in fire‐prone landscapes around the world, but these hydro‐geomorphic responses have been found to be highly variable and difficult to predict. Some variations have been observed to be associated with landscape aridity, which in turn can influence soil hydraulic properties. However, to date there has been no attempt to systematically evaluate the apparent relations between aridity and post‐wildfire runoff. In this study, five sites in a wildfire burnt area were instrumented with rainfall‐runoff plots across an aridity index (AI) gradient. Surface runoff and effective rainfall were measured over 10 months to allow investigation of short‐ (peak runoff) and longer‐term (runoff ratio) runoff characteristics over the recovery period. The results show a systematic and strong relation between aridity and post‐wildfire runoff. The average runoff ratio at the driest AI site (33.6%) was two orders of magnitude higher than at the wettest AI site (0.3%). Peak runoff also increased with AI, with up to a thousand‐fold difference observed during one event between the driest and wettest sites. The relation between AI, peak 15‐min runoff (Q₁₅) and peak 15‐min rainfall intensity (I₁₅) (both in mm h^‐1) could be quantified by the equation: Q₁₅ = 0.1086I₁₅ × AI ^2.691 (0.65<AI<1.80, 0<I₁₅<45) (adjusted r² = 0.84). The runoff ratios remained higher at drier AI sites (AI 1.24 and 1.80) throughout the monitoring period, suggesting higher AI also lengthens the window of disturbance after wildfire. The strong quantifiable link which this study has determined between AI and post‐wildfire surface runoff could greatly improve our capacity to predict the magnitude and location of hydro‐geomorphic processes such as flash floods and debris flows following wildfire, and may help explain aridity‐related patterns of soil properties in complex upland landscapes. Copyright © 2018 John Wiley & Sons, Ltd.  相似文献   

Adsorption Characteristics of Reactive Black 5 from Aqueous Solution onto Chitosan     

Tapan K. Saha  Nikhil C. Bhoumik  Subarna Karmaker  Mahmooda G. Ahmed  Hideki Ichikawa  Yoshinobu Fukumori 《洁净——土壤、空气、水》2011,39(10):984-993

Adsorption of reactive black 5 (RB5) from aqueous solution onto chitosan was investigated in a batch system. The effects of solution pH, initial dye concentration, and temperature were studied. Adsorption data obtained from different batch experiments were modeled using both pseudo first‐ and second‐order kinetic equations. The equilibrium adsorption data were fitted to the Freundlich, Tempkin, and Langmuir isotherms over a dye concentration range of 45–100 µmol/L. The best results were achieved with the pseudo second‐order kinetic and Langmuir isotherm equilibrium models, respectively. The equilibrium adsorption capacity (q_e) was increased with increasing the initial dye concentration and solution temperature, and decreasing solution pH. The chitosan flakes for the adsorption of the dye was regenerated efficiently through the alkaline solution and was then reused for dye removal. The activation energy (E_a) of sorption kinetics was estimated to be 13.88 kJ/mol. Thermodynamic parameters such as changes in free energy (ΔG), enthalpy (ΔH), and entropy (ΔS) were evaluated by applying the van't Hoff equation. The thermodynamics of reactive dye adsorption by chitosan indicates its spontaneous and endothermic nature.  相似文献   

Three‐term inversion of prestack seismic data using a weighted l2, 1 mixed norm          下载免费PDF全文

Daniel O. Pérez  Danilo R. Velis  Mauricio D. Sacchi 《Geophysical Prospecting》2017,65(6):1477-1495

We present a new inversion method to estimate, from prestack seismic data, blocky P‐ and S‐wave velocity and density images and the associated sparse reflectivity levels. The method uses the three‐term Aki and Richards approximation to linearise the seismic inversion problem. To this end, we adopt a weighted mixed l_{2, 1}‐norm that promotes structured forms of sparsity, thus leading to blocky solutions in time. In addition, our algorithm incorporates a covariance or scale matrix to simultaneously constrain P‐ and S‐wave velocities and density. This a priori information is obtained by nearby well‐log data. We also include a term containing a low‐frequency background model. The l_{2, 1} mixed norm leads to a convex objective function that can be minimised using proximal algorithms. In particular, we use the fast iterative shrinkage‐thresholding algorithm. A key advantage of this algorithm is that it only requires matrix–vector multiplications and no direct matrix inversion. The latter makes our algorithm numerically stable, easy to apply, and economical in terms of computational cost. Tests on synthetic and field data show that the proposed method, contrarily to conventional l₂‐ or l₁‐norm regularised solutions, is able to provide consistent blocky and/or sparse estimators of P‐ and S‐wave velocities and density from a noisy and limited number of observations.  相似文献   

Mesopause temperatures calculated from the O2(a 1<Delta> g ) twilight airglow emission recorded at Maynooth (53.2°N, 6.4°W)     

F. J. Mulligan  J. M. Galligan 《Annales Geophysicae》1995,13(5):558-566

Spectra of the O₂(a¹_g) airglow emission band at 1.27 µm have been recorded during twilight at Maynooth (53.2°N, 6.4°W) using a Fourier transform spectrometer. Synthetic spectra have been generated for comparison with the recorded data by assuming a particular temperature at the emitting altitude, and modelling the absorption of each line in the band as it propagates downward through the atmosphere. The temperature used in generating the synthetic spectra was varied until an optimum fit was obtained between the recorded and synthetic data; this temperature was then attributed to the altitude of the emitting layer. Temperatures derived using this technique for 91 twilight periods over an 18-month period exhibit a strong seasonal behaviour with a maximum in winter and minimum in summer. Results from this study are compared with temperatures calculated from the OH(3, 1) Meinel band recorded simultaneously. In winter OH temperatures exceed O₂ values by about 10 K, whereas the opposite situation pertains in summer; this result is interpreted in terms of a possible change in the altitude of the mesopause as a function of season. Estimates of the twilight O₂(0, 0) total band intensity indicate that its intensity is lower and that its decay is more rapid in summer than in winter, in agreement with earlier observations.  相似文献   

How do the rain rates of sub‐event intervals such as the maximum 5‐ and 15‐min rates (I5 or I30) relate to the properties of the enclosing rainfall event?     

David L. Dunkerley 《水文研究》2010,24(17):2425-2439

  相似文献   

3D description and inversion of reflection moveout of PS‐waves in anisotropic media     

Ilya Tsvankin  Vladimir Grechka† 《Geophysical Prospecting》2002,50(3):301-316

Common‐midpoint moveout of converted waves is generally asymmetric with respect to zero offset and cannot be described by the traveltime series t²(x²) conventionally used for pure modes. Here, we present concise parametric expressions for both common‐midpoint (CMP) and common‐conversion‐point (CCP) gathers of PS‐waves for arbitrary anisotropic, horizontally layered media above a plane dipping reflector. This analytic representation can be used to model 3D (multi‐azimuth) CMP gathers without time‐consuming two‐point ray tracing and to compute attributes of PS moveout such as the slope of the traveltime surface at zero offset and the coordinates of the moveout minimum. In addition to providing an efficient tool for forward modelling, our formalism helps to carry out joint inversion of P and PS data for transverse isotropy with a vertical symmetry axis (VTI media). If the medium above the reflector is laterally homogeneous, P‐wave reflection moveout cannot constrain the depth scale of the model needed for depth migration. Extending our previous results for a single VTI layer, we show that the interval vertical velocities of the P‐ and S‐waves (V_P0 and V_S0) and the Thomsen parameters ε and δ can be found from surface data alone by combining P‐wave moveout with the traveltimes of the converted PS(PSV)‐wave. If the data are acquired only on the dip line (i.e. in 2D), stable parameter estimation requires including the moveout of P‐ and PS‐waves from both a horizontal and a dipping interface. At the first stage of the velocity‐analysis procedure, we build an initial anisotropic model by applying a layer‐stripping algorithm to CMP moveout of P‐ and PS‐waves. To overcome the distorting influence of conversion‐point dispersal on CMP gathers, the interval VTI parameters are refined by collecting the PS data into CCP gathers and repeating the inversion. For 3D surveys with a sufficiently wide range of source–receiver azimuths, it is possible to estimate all four relevant parameters (V_P0, V_S0, ε and δ) using reflections from a single mildly dipping interface. In this case, the P‐wave NMO ellipse determined by 3D (azimuthal) velocity analysis is combined with azimuthally dependent traveltimes of the PS‐wave. On the whole, the joint inversion of P and PS data yields a VTI model suitable for depth migration of P‐waves, as well as processing (e.g. transformation to zero offset) of converted waves.  相似文献   

A multicatchment analysis of headwater and downstream temperature effects from contemporary forest harvesting          下载免费PDF全文

Kevin D. Bladon  Catalina Segura  Nicholas A. Cook  Sharon Bywater‐Reyes  Maryanne Reiter 《水文研究》2018,32(2):293-304

Stream temperature is a key physical water‐quality parameter, controlling many biological, chemical, and physical processes in aquatic ecosystems. Maintenance of cool stream temperatures during summer is critical for high‐quality aquatic habitat. As such, transmission of warm water from small, nonfish‐bearing headwater streams after forest harvesting could cause warming in downstream fish‐bearing stream reaches with negative consequences. In this study, we evaluate (a) the effects of contemporary forest management practices on stream temperature in small, headwater streams, (b) the transmission of thermal signals from headwater reaches after harvesting to downstream fish‐bearing reaches, and (c) the relative role of lithology and forest management practices in influencing differential thermal responses in both the headwater and downstream reaches. We measured summer stream temperatures both preharvest and postharvest at 29 sites—12 upstream sites (4 reference, 8 harvested) and 17 downstream sites (5 reference, 12 harvested)—across 3 paired watershed studies in western Oregon. The 7‐day moving average of daily maximum stream temperature (T_7DAYMAX) was greater during the postharvest period relative to the preharvest period at 7 of the 8 harvested upstream sites. Although the T_7DAYMAX was generally warmer in the downstream direction at most of the stream reaches during both the preharvest and postharvest period, there was no evidence for additional downstream warming related to the harvesting activity. Rather, the T_7DAYMAX cooled rapidly as stream water flowed into forested reaches ~370–1,420 m downstream of harvested areas. Finally, the magnitude of effects of contemporary forest management practices on stream temperature increased with the proportion of catchment underlain by more resistant lithology at both the headwater and downstream sites, reducing the potential for the cooling influence of groundwater.  相似文献   

Estimation of evapotranspiration and its components from an apple orchard in northwest China using sap flow and water balance methods     

Daozhi Gong  Shaozhong Kang  Limin Yao  Lu Zhang 《水文研究》2007,21(7):931-938

Field experiments were conducted to investigate the effects of leaf area index and soil moisture content on evapotranspiration and its components within an apple orchard in northwest China for 2 years. Evapotranspiration in the non‐rainfall period was estimated using two approaches: the soil water balance method based on tube‐type time‐domain reflection measurements, and sap flow plus micro‐lysimeter methods. The two methods were in good agreement, with differences usually less than 10%. The components of evapotranspiration varied with canopy development. During spring and autumn, soil evaporation was dominating as result of low leaf area index. In summer, plant transpiration became significant, with an average transpiration to evapotranspiration ratio of 0·87. The crop coefficient K_c showed a strong linear dependence on leaf area index. The water stress coefficient K_s was around 1·0 when soil moisture was above 23% and started to decrease linearly after that. This study demonstrates that prediction of evapotranspiration in apple orchards can be made using the Food and Agriculture Organization's crop coefficient method from commonly available meteorological data in the area. Copyright © 2006 John Wiley & Sons, Ltd.  相似文献