共查询到20条相似文献，搜索用时 15 毫秒
1.
I. O. Leont’yev 《Oceanology》2008,48(1):123-128
A method based on mathematical modeling of the near-shore dynamics is suggested to calculate the annual mean cross-shore sediment flux q* at the coastal zone boundary. This method is applied to several sand coast profiles located in various geographical regions and exposed to energetic impacts of different scale. It is shown that the fluxes can be either positive (directed to the shore) or negative, and the magnitudes found agree with the known estimates based on other approaches. A conclusion is made that the resulting direction of q* is controlled by moderate storms with regime cumulative exedence from 1 to 10%. The wave periods, bottom slope, and sediment grain size play a special role in the process. An empirical criterion is found that allows one to predict the direction of the sediment flux crossing the coastal zone boundary. 相似文献
2.
Reasons for the nonclosure of the heat balance in the atmospheric boundary layers over natural land surfaces are analyzed. Results of measuring the heat-balance components over different land surfaces are used. The Cabauw (Netherlands) data (obtained throughout 1996 over a grass surface with intermittent shrubs and single trees) and the data from the Anchor station in Germany (measured over coniferous forest in 2000–2001) are analyzed. In all, the analysis involves about fifty thousand independent values of the heat-balance components measured in the experiments, which should be indicative of the reliability of the results obtained in the paper. The data have shown that the heat balance is not closed and the imbalance is 50–250 W/m2. The sum of the latent and sensible heat fluxes λE + H = STF is found to be systematically smaller than the difference between the net radiation and the heat flux into the ground R n ? G. It is shown that the main cause of a systematic heat imbalance in the atmospheric boundary layers over inhomogeneous land surfaces is that the methods of surface-flux measurement and estimation are based on the theory that requires the hypothesis of stationarity and horizontal homogeneity. Direct data analysis has shown that the heat imbalance increases with landscape inhomogeneity. In the paper, a parametrization of the heat imbalance is carried out and the coefficient k f (z 0 ef /L ef ) is introduced as a measure of inhomogeneity. For this, data from the experiments FIFE, KUREX, TARTEX, SADE, etc., are also used. Empirical formulas are presented to refine the results of direct measurements and calculations of surface fluxes over natural (inhomogeneous) land surfaces from profile and standard (using bulk parametrizations) data. These formulas can also be used to determine surface fluxes over inhomogeneous underlying land surfaces in order to take into account so-called subgrid-scale effects in constructing prediction models. 相似文献
3.
Results obtained from simulating the propagation of infrasonic waves from the Chelyabinsk meteoroid explosion observed on February 15, 2013, are given. The pseudodifferential parabolic equation (PDPE) method has been used for calculations. Data on infrasonic waves recorded at the IS31 station (Aktyubinsk, Kazakhstan), located 542.7 km from the likely location of the explosion, have been analyzed. Six infrasonic arrivals (isolated clearly defined pulse signals) were recorded. It is shown that the first “fast” arrival (F) corresponds to the propagation of infrasound in a surface acoustic waveguide. The rest of the arrivals (T1–T5) are thermospheric. The agreement between the results of calculations based on the PDPE method and experimental data is satisfactory. The energy E of the explosion has been estimated using two methods. One of these methods is based on the law of conservation of the acoustic pulse I, which is a product of the wave profile area S/2 of the signal under analysis and the distance to its source E I [kt] = 1.38 × 10–10 (I [kg/s])1.482. The other method is based on the relation between the energy of explosion and the dominant period T of recorded signal E T [kt] = 1.02 × (T [s]2/σ)3/2, where σ is the dimensionless distance determining the degree of nonlinear effects during the propagation of sound along ray trajectories. According to the data, the explosion energy E I,T ranges from 1.87 to 32 kt TNT. 相似文献
4.
河口有色溶解有机物（colored dissolved organic matter,CDOM）的分布是各种物理-生物地球化学过程共同作用的结果。为实现河口高动态变化CDOM的监测，遥感是一种重要的手段。由珠江口四个不同季节的航次获得的实测数据，本文构建了一个遥感算法以反演CDOM在400 nm的吸收系数（aCDOM （400））。该算法使用以波段反射率比值Rrs （667）/Rrs （443）和Rrs （748）/Rrs （412）为自变量。将构建的算法应用于2002-2014年的MODIS/Aqua数据，本文计算了珠江口不同季节的aCDOM （400）气候态分布。CDOM的分布主要受珠江径流量和区域水下地形特征的影响。沿着垂直于水深梯度的断面，气候态aCDOM （400）呈指数减少（y=aebx,b<0），但不同季节差异很大。珠江口CDOM主要是河流淡水输运而来。其中，富里酸比例随盐度的增加而降低。基于构建的算法、CDOM保守混合方程和径流量，本文由MODIS/Aqua数据进一步估算了2002-2014年夏季和冬季珠江DOC的有效入海浓度和有效入海通量。珠江的有效入海浓度和有效入海通量都与流量存在正相关关系，且在夏季的相关性更明显，R2分别为0.698和0.9657。 相似文献
5.
Nikuradse roughness (ks) is very important in the sediment transport prediction because it is related to the evaluations of the velocity distribution, shear stress and erosion depth. Dimensionless Nikuradse roughness (ks/D, where D is the sediment diameter) is usually given 1–2.5 on the immobile plan bed or at low shear stress. But it behaves differently on the mobile plan bed at high shear stress with much sediment picked up to movement when the Shields parameter (Θ) is larger than 0.8–1.0. The effective Nikuradse roughness on the mobile plan bed was derived indirectly from the erosion depth correlated to the mobile plan bed thickness considering the mass conservation in the present study. The proposed erosion depth confirmed the relation to the Shields parameters with an extra factor consisting of suspended sediment and its damping to turbulence. The decrement of the erosion depth caused by the increment of the sediment diameter at large shear stress was obtained, which was usually absent in classical empirical formulas based on the bedload theory. Good agreement with experiments was achieved by the present prediction of the Nikuradse roughness, erosion depth and sediment transport rate. Discussion was mainly focused on the prediction improvement caused by considering the impact of suspended sediment and its damping to turbulence. 相似文献
6.
The present work aimed to study the influence of mercuric chloride (HgCl2) on pigment content (chlorophyll a and pheophytin) in sediment traps on the basis of experimental data. The marine microalgal cultures of Conticribra weissflogii (Mediophyceae), Tetraselmis viridis (Chlorodendrophyceae), Amphidinium carterae (Dinophyceae), Nannochloropsis sp. (Eustigmatophyceae) were used. The obtained results revealed that the influence of mercury on pigment content as well as on photosynthetic activity was different in different species. The considerable decrease in phytopigments content was observed in Amphidinium carterae and Conticribra weissflogii, while the proportion of pheophytin increased. The pigment content of Tetraselmis viridis was not different from the control line, while for Nannochloropsis sp. the increase in pigment concentration was noticed. The complete immediate inhibition of photosynthetic activity was observed in Conticribra weissflogii, Tetraselmis viridis, Amphidinium carterae, while Nannochloropsis sp. responded only after 24 h of exposition. The pigment degradation rate was almost the same for diatoms and dinoflagellates. The equation for estimating the phytopigments content in sediment traps, that takes into consideration the exposition time, is proposed. 相似文献
7.
Plankton respiration is an important part of the carbon cycle and significantly affects the balance of autotrophic assimilation and heterotrophic production in oceanic ecosystems. In the present study, respiration rates of the euphotic zone plankton community(CR_(eu)), size fractionated chlorophyll a concentration(Chl a), bacterial abundance(BAC), and dissolved oxygen concentration(DO) were investigated during winter and summer in the northern South China Sea(n SCS). The results show that there were obvious spatial and temporal variations in CR_(eu) in the n SCS(ranging from 0.03 to 1.10 μmol/(L·h)), CR_(eu) in winter((0.53±0.27) μmol/(L·h)) was two times higher than that in summer((0.26±0.20) μmol/(L·h)), and decreased gradually from the coastal zone to the open sea. The distribution of CR_(eu) was affected by coupled physical-chemical-biological processes, driven by monsoon events. The results also show that CR_(eu) was positively correlated with Chl a, BAC, and DO, and that BAC contributed the highest CR_(eu) variability. Furthermore, the results of the stepwise multiple linear regression suggest that bacteria and phytoplankton were the dominant factors in determining CR_(eu)(R~2 = 0.82, p0.05) in the n SCS. Based on this relationship, we estimated the integrated water column respiration rate(CRint) within 100 m of the investigated area, and found that the relationship between the biomass of the plankton community and respiration may be nonlinear in the water column. 相似文献
8.
Based on long-term (1985–1995) monitoring data, the paper considers the peculiarities of seasonal variability in the spatial and vertical distribution of particulate organic phosphorus (РPOM) in the surface layer and in the photosynthetic zone in the northwestern Black Sea. Regression equations, experimental data, and satellite observations for the chlorophyll a concentration allowed us to evaluate the seasonal longterm (1979–1995) variability in РPOM in the surface layer and photosynthesis zone. The ratios of the concentrations of particulate organic carbon, nitrogen, phosphorus, and chlorophyll a are calculated and statistical estimates of seasonal changes in the РPOM in the areas with different degrees of influence of river runoff and water of open seas are obtained. The consistency of intra-annual changes in the concentrations of РPOM, chlorophyll a, and phytoplankton biomass is shown, which indicates the role of phytoplankton in the formation of РPOM and in its intra- and interannual variability in the northwestern part of the sea. It is shown that long-term seasonal variations in РPOM and related changes in the concentration of chlorophyll a depend on the variability of bulk river runoff, the extent of its abundance in the northwestern shelf, and regional hydrometeorological conditions. 相似文献
9.
The deviations of the marine surface slope spectra (measured using an array of wave gauge sensors) from the theoretical estimates obtained using the linear spectral model of the wave field are analyzed. It has been indicated that the average measured full slope spectra (the sum of the slope component spectra in the orthogonal directions) is higher than the theoretical estimates by 6% at frequencies from the surface wave spectral peak (f m ) to 4.5 f m . The difference between the measured and theoretical estimates of the full slope spectrum rapidly increases at frequencies of f < f m . At f m ≈ 0.75 f m , the average measured full slope spectrum is higher than the theoretical estimate by a factor of more than 5. 相似文献
10.
2012年夏季海南岛东岸上升流区的混合观测 总被引：1，自引：0，他引：1
The turbulent mixing in the upwelling region east of Hainan Island in the South China Sea is analyzed based on in situ microstructure observations made in July 2012. During the observation, strong upwelling appears in the coastal waters, which are 3℃ cooler than the offshore waters and have a salinity 1.0 greater than that of the offshore waters. The magnitude of the dissipation rate of turbulent kinetic energy ε in the upwelling region is O(10–9 W/kg), which is comparable to the general oceanic dissipation. The inferred eddy diffusivity K_ρ is O(10–6 m~2/s), which is one order of magnitude lower than that in the open ocean. The values are elevated to K_ρ≈O(10–4 m~2/s) near the boundaries. Weak mixing in the upwelling region is consistent with weak instability as a result of moderate shears versus strong stratifications by the joint influence of surface heating and upwelling of cold water.The validity of two fine-scale structure mixing parameterization models are tested by comparison with the observed dissipation rates. The results indicate that the model developed by Mac Kinnon and Gregg in 2003 provides relatively better estimates with magnitudes close to the observations. Mixing parameterization models need to be further improved in the coastal upwelling region. 相似文献
11.
双壳类适应性进化遗传基础尚未有大量研究。而生活在沿海潮间带和深海环境中的双壳贝类适应性进化的分子机制更鲜有报道。我们首次测序组装了潮间带生活的偏顶蛤Modiolus modiolus的转录组序列。同时与生活在深海热液冷泉喷口的偏顶蛤Bathymodiolus platifrons进行了比较转录组分析，阐明了这两个物种在不同环境中的适应性进化机制。M. modiolus和B. platifrons的转录组组装共产生182，476和156，261个转录本，N50值分别为1，769和1，545。同时注释到27，868和23，588个基因。GO富集分析表明这些基因有相似的富集模式。两物种进化分析鉴定到10，245个直系同源基因，其中26个基因受到强烈正选择（Ka/Ks＞1），12个基因受到中度正选择（0.5M. modiolus的转录组组装拼接序列，同时通过比较转录组学分析阐明了其与近缘物种B. platifrons的适应性进化机制。这为两个物种后续研究提供了序列资源和研究基础。 相似文献
12.
腹壁纤毛虫是一种附着在浮游动物上的原生生物，尤其是附着在桡足类和甲壳类上的。而缘毛虫是可以以自由或寄生的形式在世界各沿海地区和港湾处被发现。本研究首次对东印度洋表层至200 m深海域的缘毛类纤毛虫以及其水平分布展开了研究。根据纤毛虫的形态、纤毛结构和茎的形态等的特征，在2014年4月10日至5月13日东印度洋航次的浮游生物拖网样品中鉴定出了五种富腹纤毛虫，海洋钟形虫Vorticella oceanica、交替聚缩虫Zoothamnium alternans、阿拉聚缩虫Zoothamnium alrasheidi、远洋聚缩虫Zoothamnium pelagicum和海洋聚缩虫Zoothamnium marinum。并通过光显微镜和扫描显微镜拍摄的照片，说明了其形态、尺寸和特征。研究结果表明，海洋钟形虫和远洋聚缩虫的分布与硅藻（如，密聚角毛藻Chaetoceros coarctatus）和桡足类（如，短角长腹剑水蚤Oithona brevicornis）等寄主有关，也包括甲藻（如，三角角藻Ceraitum tripose）周围的一些个体。这些附着纤毛虫的分布在东印度洋海域东南区以海洋钟形虫、远洋聚缩虫和海洋聚缩虫为主，而在孟加拉湾北部则有大量的阿拉聚缩虫。这种分布的变化可能是与寄主的分布有关，如桡足类（短角长腹剑水蚤）和硅藻（密聚角毛藻）的分布影响。 相似文献
13.
N. P. Romanov 《Izvestiya Atmospheric and Oceanic Physics》2009,45(6):799-804
Instead of approximation formula ln(E(t)/E(0)) = [(a ? bt)t/(c + T)] commonly used at present for representing dependence of pressure of saturated streams of liquid water E upon temperature we suggested new approximation formula of greater accuracy in the form ln(E(t)/E(0)) = [(A ? Bt + Ct 2)t/T], where t and T are temperature in °C and K respectively. For this formula with parameters A = 19.846, B = 8.97 × 10?3, C = 1.248 × 10?5 and E(0) = 6.1121 GPa with ITS-90 temperature scale and for temperature range from 0°C to 110°C relative difference of approximation applying six parameter formula by W. Wagner and A. Pruß 2002, developed for positive temperatures, is less than 0.005%, that is approximately 15 times less than accuracy obtained with the firs formula. Increase of temperature range results in relative difference increasing, but for even temperature range from 0°C to 220°C it does not higher than 0.1%. For negative temperatures relative difference between our formula and a formula of D. M. Murphy and T. Koop, 2005, is less than 0.1% for temperatures higher than ?25°C. This paper also presents values of coefficients for approximation of Goff and Grach formula recommended by IMO. The procedure of finding dew point T d for known water steam pressure e n based on our formula adds up to solving an algebraic equation of a third degree, which coefficients are presented in this paper. For simplifying this procedure this paper also includes approximation ratio applying a coefficient A noted above, in the form T d (e n ) = \(\frac{{AT_0 }}{{A - \varepsilon }}\) + 0.0866?2 + 0.0116?10/3, where ? = ln(e n /E(T 0)). Error of dew point recovery in this ratio is less than 0.005 K within the range from 0 to 50°C. 相似文献
14.
The results of a simulation of the combined tidal ice drift corresponding to a linear superposition of the M 2, S 2, K 1, and O 1 harmonics of the tidal generating force are discussed. Also, ice-induced maximal (during the tropical month, i.e., over 27.322 mean solar days) values of the dynamic and energy characteristics of combined motions are estimated in the marginal seas of the Siberian continental shelf. Special attention was paid to the revealing of zones of compression-rarefaction and zones of ice floe ridging. 相似文献
15.
The spatiotemporal variability of equatorial Pacific upper ocean heat content (HC) and subsurface heat during two types of El Niño-Southern Oscillation (ENSO), namely eastern and central Pacific (EP and CP) types, is investigated using subsurface ocean heat budget analysis. Results show that HC tendencies during both types of ENSO are mainly controlled by oceanic heat advection beneath the mixed layer to the thermocline, and the role of net surface heat flux can be neglected. The most important three terms are the zonal and vertical advections of anomalous heat by climatological currents (QU 0 T′, QW 0 T′) and zonal advection of climatological heat by anomalous current (QU′T 0). The large contribution of QU 0 T′ extends from west to east along the equatorial Pacific. The considerable contribution of QU′T 0 is confined to the east of 160°W, and that of the QW 0 T′ is observed in the central Pacific between 180°E and 120°W. In particular, a major contribution of QW 0 T′ is also observed in the far eastern Pacific east of 100°W during EP ENSO. There is also a small contribution from meridional advection of climatological heat by anomalous current (QV′T 0). In contrast, the meridional advection of anomalous heat by climatological currents (QV 0 T′) and vertical advection of climatological heat by anomalous current (QW′T 0) are two damping factors in the HC tendency, with the former dominating. Differences in spatial distribution of the heat advection associated with the two types of ENSO are also presented. We define a warm water heat index (WWH) as integrated heat content above 26 kg m?3 potential density (26σ ? ) isopycnal depth within 130°E–80°W and 5°S–5°N. Further examination suggests that the recharge–discharge of WWH is involved in both types of El Niño, though with some differences. First, it takes about 42 (55) months for the evolution of a recharge–discharge cycle during an EP (CP) ENSO. Second, the EP El Niño event peaks during the discharge phase, 7–8 months after the recharge time. The CP El Niño peaks during the recharge phase, 4–5 months before the recharge time. The locations of HC anomalies in the El Niño mature phase relative to those at recharged time explain why the EP and CP El Niño peak in different stages of the recharge–discharge process. 相似文献
16.
Both horizontal and vertical heat exchanges and feedbacks between air temperature and anthropogenic heat fluxes significantly affect the characteristics of the urban heat island (UHI). The UHI intensity depends, in particular, on the ratio between the scales LA (area of anthropogenic forcing) and Lγ (distance passed by an air particle of the oncoming stably stratified flow before its temperature approaches air temperature within the UHI). Both advection and feedback effects may be estimated based on the equation for the local heat balance of the underlying surface. In this case, heat advection is taken into account by calculating temperatures individually for the atmospheric boundary layer and the surface of the urban canopy layer. The estimates show that the asymptotics of strong advection is more characteristic of a typical city. However, under weak winds, with consideration for the feedback between air temperature and anthropogenic heat flux, some deviations from this asymptotics are probable. 相似文献
17.
Venigalla Purnachandra Rao Pratima Mohan Kessarkar Meloth Thamban Shiva Kumar Patil 《Journal of Oceanography》2010,66(1):133-146
Geochemical and rock-magnetic investigations were carried out on a sediment core collected from the SE Arabian Sea at 1420 m depth in oxygenated waters below the present-day oxygen minimum zone. The top 250 cm of the core sediments represent the last 35 kaBP. The · 18O values of Globigerinoides ruber are heaviest during the Last Glacial Maximum (LGM) and appear unaffected by low-saline waters transported from the Bay of Bengal by the strong northeast monsoon and West Indian coastal current. The signatures of Bølling-Allerød and Younger Dryas events are distinct in the records of magnetic susceptibility, organic carbon (OC) and · 18O. Glacial sediments show higher OC, CaCO3, Ba, Mo, U and Cd, while the early-to-late Holocene sediments show increasing concentrations of OC, CaCO3, Ba, Cu, Ni and Zn and decreasing concentrations of Mo, U and Cd. Productivity induced low-oxygenated bottom waters and reducing sedimentary conditions during glaciation, and productivity and oxygenated bottom waters in the Holocene are responsible for their variation. The core exhibits different stages of diagenesis at different sediment intervals. The occurrence of fine-grained, low-coercivity, ferrimagnetic mineral during glacial periods is indicative of its formation in organic-rich, anoxic sediments, which may be analogous to the diagenetic magnetic enhancement known in sapropels of the Mediterranean Sea and Japan Sea. The glacial sediments exhibiting reductive diagenesis with anoxic sedimentary environment in this core correspond to reductive diagenesis and intermittent bioturbation (oxygenation) reported in another core in the vicinity. This suggests that the poorly oxygenated bottom water conditions during glacial times should not be generalized, but are influenced locally by productivity, sedimentation rates and sediment reworking. 相似文献
18.
为节约成本和样品，一些学者同时分析海洋沉积物中的碳、氮及其同位素（TOC、TN、δ13C和δ15N）。分析沉积物中的δ13C，需要对样品进行酸化去除无机碳，但是这一酸化过程会使TN和δ15N的分析结果产生偏差，且偏差范围与沉积物中无机碳含量（CaCO3）有关。本研究选取了低CaCO3含量（1-16%）和高CaCO3含量（20-40%）的海洋沉积物样品，比较了酸化过程对TN和δ15N的影响。研究结果表明，酸化过程对海洋沉积物中TN和δ15N的分析结果产生了显著影响。对于低CaCO3含量的样品，酸化导致样品中TN流失了约0-40%，δ15N偏移了约0-2‰；而对于高CaCO3含量的样品，酸化导致样品中TN流失了约10-60%，δ15N偏移了约1-14‰。表明酸化对TN和δ15N的影响已经超过了仪器的误差范围0.002%（TN）和0.08‰（δ15N），将影响TN和δ15N的环境指示意义。因此，即使海洋沉积物样品中CaCO3含量很低，也必须用原样分析TN和δ15N以避免酸化过程的影响。 相似文献
19.
A long-term mean turbulent mixing in the depth range of 200–1000 m produced by breaking of internal waves across the middle and low latitudes (40°S–40°N) of the Pacific between 160°W and 140°W is examined by applying fine-scale parameterization depending on strain variance to 8-year (2005–2012) Argo float data. Results show that elevated turbulent dissipation rate (ε) is related to significant topographic regions, along the equator, and on the northern side of 20°N spanning to 24°N throughout the depth range. Two patterns of latitudinal variations of ε and the corresponding diffusivity (Kρ) for different depth ranges are confirmed: One is for 200–450 m with significant larger ε and Kρ, and the maximum values are obtained between 4°N and 6°N, where eddy kinetic energy also reaches its maximum; The other is for 350–1000 m with smaller ε and Kρ, and the maximum values are obtained near the equator, and between 18°S and 12°S in the southern hemisphere, 20°N and 22°N in the northern hemisphere. Most elevated turbulent dissipation in the depth range of 350–1000 m relates to rough bottom roughness (correlation coefficient?=?0.63), excluding the equatorial area. In the temporal mean field, energy flux from surface wind stress to inertial motions is not significant enough to account for the relatively intensified turbulent mixing in the upper layer. 相似文献
20.
Che Din Mohd Safuan Azizi Ali Zuraini Zainol Ahmad Ali Mohd Fadzil Mohd Akhir Aidy M. Muslim Zainudin Bachok 《Ocean Science Journal》2018,53(2):275-283
Coral reefs along the Malacca Straits (MS) are poorly developed mainly due to turbidity and sedimentation. This study describes the health status and community structure of the corals in Cape Rachado, West Coast of Peninsular Malaysia (WCPM), utilizing the Coral Video Transect (CVT) technique. All the survey transects were categorized as ‘fair’ coral conditions (27.39 ± 5.41%–48.56 ± 18.96%) with the reef floor mainly covered by corals and sediment. Twelve families of coral comprised of 25 distinct genera were identified. Coral communities were differentiated into four clusters with each being predominated by Galaxea, Diploastrea, Fungia and Pectinia respectively. Among all, Pectinia is the most spectacular genera and dominated the survey area. Along the MS, Favia, Favites and Porites are commonly found while Porites and Pectinia dominated the reefs. Low coral cover and diversity was recorded in MS as compared to the reefs in the South China Sea (SCS). The most prominent results include changes in the dominant coral from Porites to Pectinia while some species such as Acropora were absent from the study area. Based on the presented data, the reef in the study area was predominantly occupied by sediment and the coral communities were formed by a species with a high tolerance to turbidity and sedimentation. 相似文献