A note on the joint distribution of wave height and period during the growth phase of a storm

In this note the effect of changes in sea-state, as measured by the significant wave heigh H_s, on the joint distribution of individual wave height and period are considered. Wave data, obtained from a Waverider buoy during the growth phase of a storm, are used in the analysis. It is found that, by correctly scaling the individual heights and periods, the form of the joint distribution does not depend on H_s, but is dependent on the bandwidth of the spectrum. The results obtained also give some indication of the period of individual, high zero-upcrossing waves.     

A generalized approach for long-term modelling of extreme crest-to-trough wave heights

This paper deals with the long-term modelling of high sea waves. The solution is given for the return period of sea storms during which an arbitrary chosen number of waves, with crest-to-trough heights exceeding a fixed threshold, occur. This return period is derived starting from the Equivalent Triangular Storm (ETS) model, which associates a triangle to each actual storm and thus represents a significant wave height time series at a fixed location by means of a sequence of triangular storms. The short-term statistics is then applied to investigate the occurrence of large crest-to-trough wave heights during a given storm. Finally, by combining the statistical distribution of significant wave heights, the ETS model and the short-term wave statistics, the solution is given for the return periods R_N and R_N of a sea storm in which N or at least N waves higher than a fixed threshold occur. The values of R_N are then calculated, starting from data of two buoys moored in the Pacific Ocean and in the Mediterranean Sea.     

Effects of geomagnetic disturbances in the near Earth’s atmosphere and possible biophysical mechanism of their influence on the human cardiovascular system

We analyze the effect of geomagnetic activity on variations in quasi-static electric field strength and the horizontal geomagnetic field component in the band of periods of tidal and planetary waves. Variations in oscillation intensities and periods in the power spectra of these parameters synchronously with the K _p index are shown. Taking into account the relationship of these parameters with the air pressure, we suggest a possible biophysical mechanism of the relation between the state of the human cardiovascular system and geomagnetic activity by means of resonant interaction with the environment. In periods of high geomagnetic activity, the air pressure and temperature vary due to an increase in atmospheric transparency as a result of the Forbush decrease in the cosmic ray flux rate. It is these variations that directly affect humans.     

Response of a two-layer ocean with a baroclinic current to a moving storm,part II

A circular storm moves with a constant speedc along a geostrophic flow similar to a western boundary current in the upper layer of a two-layer ocean with the motionless lower layer. The linear inertia terms are retained. Effects of the current becomes more conspicuous for smallerc and insignificant forc above 10 m s^–1. The inertia effects are manifested in cellular patterns of the interface perturbations with cell lengths of(c–vf ^–1 in a wake of the storm with a radius of an order of 100 km, wherev is the current velocity. On the left hand edge where the flow has a strong shear, the interface displacements have large amplitudes which increase with a distance along the path in a wake of the storm. These disturbances propagate to the left of the edge within an angle of cot^–1 (c ²/gH₀–1), whereg is the reduced gravity andH ₀ is the depth of the interface at the edge of the current. Comparison with the observations during Typhoon Trix in 1971 south of Japan suggests that fluctuations of the daily mean sea level with several days' periods observed along the southern coast of Japan may be due to the stationary oscillations of the Kuroshio caused by the inertia undulations along its left edge or due to the propagating perturbations to the left.     

海水人工湿地系统脱氮效果与基质酶活性的相关性

利用海水人工湿地系统处理海水养殖外排水,分析了人工湿地对不同形态氮的净化效果,探讨了人工湿地表层基质酶活性变化及其对系统脱氮效果的影响。选取互花米草作为人工湿地植物,煤渣、珊瑚石和细砂作为人工湿地基质,实验期间连续进水,系统运行稳定。研究结果表明:海水人工湿地系统对氨氮(NH4-N)、亚硝态氮(NO2-N)、硝态氮(NO3-N)、总氮(TN)和可溶性有机氮(DON)去除效果显著,去除率分别为(99.6±0.7)%、(99.9±0.0)%、(98.2±2.0)%、(92.6±1.5)%和(86.1±4.8)%。人工湿地表层基质下行池脱氢酶、硝酸还原酶和脲酶的酶活性均高于上行池,下行池对污染物的去除效果更好。脱氢酶活性与海水人工湿地系统氨氮的去除有关;硝酸还原酶活性影响着海水人工湿地硝态氮的去除;脲酶活性与人工湿地总氮和硝态氮的去除存在明显相关趋势。下行池硝酸还原酶和脲酶的酶活性间具有显著相关性(r=0.76, P0.05)。人工湿地微生物种类丰富,下行池微生物多样性高于上行池,植物根部微生物多样性最高,提高了系统脱氮的效率。上述研究结果将有助于阐明海水人工湿地系统中不同形态氮的迁移转化机理。     

Biology of three Malacostraca (Decapoda) in a Mediterranean lagoon with particular emphasis on the effect of rapid environmental changes on the activity (catchability) of the species

The activity of three Malacostraca (Decapoda), Crangon crangon, Carcinus aestuarii and Paleamon squilla, was studied following rapid environmental changes in a Mediterranean lagoon linked temporarily with the sea. Nekton was sampled every 2–3 days using fixed fyke nets. A canonical analysis and a stepwise multiple regression were computed to determine which factor(s) can predict or account for the catch of these three decapods. In spite of rapid environmental changes no exceptional mortality was observed in each of the three species. Temperature is the environmental factor with major impact on the activity of C. crangon. Activity of P. squilla is controlled by water depth. At a depth of less than 20 cm two factors, salinity and phase of the moon, have a significant influence on the activity of this species. At depths deeper than 20 cm the activity is inhibited. There is only a weak relationship between the catch of C. aestuarii and salinity. Additional data on the life cycle of these species are given. The limitations of a monthly sampling period are discussed and the need for more short-term, consecutive sampling periods is stressed in order to understand the dynamics of systems with rapid environmental fluctuations.     

合浦珠母贝基质蛋白KRMP-3对二价金属离子选择性的研究

用大肠杆菌表达含有GST标签的基质蛋白KRMP-3。利用圆二色谱(Circular Dichroism, CD)研究不同浓度钙离子和镁离子对基质蛋白 KRMP-3二级结构的影响。结果表明,钙离子对其二级结构的变化远大于镁离子;同时,采用荧光淬灭法研究 KRMP-3对钙,镁,锶,钡等二价金属离子的选择性,结果表明, KRMP-3对钙离子有特异性选择性,钙离子与KRMP-3的结合常数K约为103 L/mol,结合位点数 n 近似为1,表明 KRMP-3与钙离子的结合能力适中,推测基质蛋白 KRMP-3对合浦珠母贝( Pinctada fucata)棱柱层形成起到促进作用。     

黄河三角洲互花米草整治对潮滩湿地防灾功效和沉积动力的影响

互花米草作为黄河三角洲外来入侵物种, 2010年开始爆发式蔓延, 2020年面积最大时可超6 000 hm²,对潮间带生物多样性造成了严重影响。自2020年起,黄河三角洲自然保护区开始大规模的互花米草整治与盐地碱蓬生态修复工作。互花米草具有较强的消浪、缓流、促淤、固滩能力,短期内、大范围的植被去除,可能导致波流和沉积动力环境的突变。基于现场观测数据和考虑植被作用的浪、流、沙耦合数值模型,研究分析了互花米草整治和盐地碱蓬修复对黄河三角洲湿地动力过程的影响,重点关注风暴作用下黄河三角洲潮滩湿地的防灾减灾能力和沉积效应变化。研究结果表明,互花米草可有效抵御极端风暴潮,最大风暴潮位衰减率可达15 cm/km。互花米草整治将导致湿地防灾减灾能力显著下降,堤前风暴潮峰值可抬升10～30 cm,同时潮间带的泥沙捕集能力大幅下降。受限于植被密度、高度,盐地碱蓬完全修复后湿地衰减风暴潮、捕集泥沙的能力显著低于原互花米草湿地。研究建议,互花米草整治工程应考虑短期内植被去除导致的近岸风暴潮抬升、侵蚀加剧等潜在风险。     

Pore‐water pressure measurements: Mississippi delta submarine sediments

Abstract

A pore‐water pressure probe (piezometer) was implanted in Mississippi delta sediments at a preselected site (Block 28, South Pass area, 29°00´N, 89°15´W) 145 m from an offshore production platform (water depth approx. 19 m) in September 1975. Total pore‐water pressures (u_w ) were monitored for extended periods of time at depths of approximately 15 and 8 m below the mudline concurrently with hydrostatic pressures (u₈ ) measured at depths of 15 m and approximately 1 m below the mudline. Relatively high excess pore‐water pressures, u_e = (u_w ‐u₈ ), were recorded at the time of probe insertion measuring 99 kPa (14.4 psi) at 15 m and 50 kPa (7.3 psi) at 8 m. Six hours after the probe was implanted, excess pore pressures were still high at 81 kPa (11.8 psi, 15 m) and 37 kPa (5.4 psi, 8 m). Pore pressures appeared to become relatively constant at the 8‐m depth after 7 h had elapsed, and at the 15 m depth after 10–12 h. Excess pore‐water pressures averaged 72 kPa (10.4 psi, 15 m) and 32 kPa (4.6 psi, 8 m) prior to the initial effects of Hurricane Eloise, which passed in close proximity to the probe site. Significant variations in pressures were recorded during storm activity. As the effects of the storm subsided, excess pore‐water pressures began to decline slightly at the 15‐m depth; however, concurrently at the 8‐m depth, pore pressures began to increase gradually. During the period of 21–25 days after the probe was implanted, excess pore pressures appeared to become more constant, averaging 24 kPa (3.5 psi) at 15 m and 43 kPa (6.2 psi) at the 8‐m depth. The presence of methane, a common occurrence in these delta muds, may have influenced, or contributed to, the total pore‐water pressures measured during this experiment.     

Diffusion of seawater ions. Part II. The role of activity coefficients and ion pairing

A theoretical evaluation of basic thermodynamic relationships reveals that variation of activity coefficients, ion pairing and electrical interactions must be considered when modelling ionic diffusion in seawater. The contributions of ion-pair formation and change in activity coefficient along the diffusion path were studied experimentally by conducting diffusion experiments in which solutions of KCl, NaCl, MgCl₂, Li₂SO₄, K₂SO₄, Na₂SO₄ and MgSO₄, at an ionic strength of 0.7, were allowed to diffuse into distilled water. The study reveals that the thermodynamic factor, required to correct for changes in the activity coefficient along the diffusion path, is significant for all the salts studied. Agreement between a simple diffusion model, which does not include ion pairing, and observed data was good for completely dissociated salts, but poor for salts which are known to form ion pairs at the concentration levels studied. The diffusion of MgSO₄, 0.425 of which is associated at I = 0.7, was successfully modelled by assuming that the diffusion coefficient of the MgSO₄⁰ ion pair is different from the diffusion coefficient of the dissociated salt. The diffusion coefficient of this ion pair is estimated to be 1.9 × 10⁻⁵ cm² s⁻¹ at 30°C, as compared to 0.49 × 10⁻⁵ cm² s⁻¹ for the dissociated salt. It is suggested that the high mobility of this ion pair could cause magnesium enrichment in pore water of sulfate depleted sediments.     

Relations between Sea Surface Temperature and Air-Sea Heat Flux at Periods from 1 Day to 1 Year Observed at Ocean Buoy Stations around Japan

Relations between sea-surface temperature (T _s) and heat flux at the sea surface (F) have been investigated using data from ocean observation buoys located off Shikoku in the Sea of Japan and in the East China Sea. Wavelet transformation decomposed F and T _s to wavelet coefficients (WLC) in the period-time domain. Assuming one-dimensional heat transfer by eddy diffusion in the upper ocean, the phase difference (δθ) defined as the difference between the phase of the temporal change rate of T _s, and the phase of F ranges statistically from 0 to +π/4 when F changes T _s, and is around −π/2 when heat convergence in the sea (Av) forces T _s. The δθ values are distributed from 0 to +π/4 at one-day and one-year periods at all buoys. WLC amplitude (WLCA) of F at periods from 16 to 32 day periods, which may be caused by the atmospheric ridge-trough systems, maintains energy longer than WLCA at periods from 2 to 16 days, which may be caused by monsoonal surges. At periods from 2 to 64 days, δθ values distribute from 0 to +π/4 or around −π/2 at each event, reflecting the surroundings of each ocean, i.e., Kuroshio recirculation in the off-Shikoku area, water-temperature front in the Sea of Japan, and water exchange in the continental shelf edge in the East China Sea. We demonstrate that the wavelet analysis can characterize the correspondence between irregular signals of F and T _s in various time scales and locations. This revised version was published online in August 2006 with corrections to the Cover Date.     

环礁潟湖沉积物重建南沙群岛小冰期以来的热带气旋活动

热带气旋活动以及由此产生的风暴潮和强降雨对南海及周边沿海地区社会经济构成巨大威胁。对器测记录之前全新世热带气旋的研究有助于准确预测全球变暖背景下热带气旋活动的变化趋势。本文利用南沙群岛安乐礁潟湖沉积物重建了小冰期以来准年分辨率的热带气旋活动,共识别28个风暴事件层。研究表明,小冰期以来,南沙群岛安乐礁热带气旋活动在年代际到百年尺度上频繁变化,发育两个主要的风暴活跃期。在小冰期早期(AD1471—1620)经历了最为强烈的风暴活跃期,另一个风暴活跃期位于现代暖期的AD 1930—1960,风暴活动虽有所加强,但明显低于小冰期早期。与同期永暑礁重建结果的对比表明,热带气旋活动存在明显的时空差异性,更多来自相近区域的高分辨率风暴记录可有效降低古风暴活动重建的不确定性,提高重建记录的准确度。     

A current-splitting method applied to 3-dimensional shallow-sea hydrodynamical model

The current-splitting method (CSM) for the study of ultra-shallow water storm surges proposed by the second author of the present paper is extended in this study to solve time-dependent problems. In the previous method the zero-order horizontal currents in the 3-dimensional storm surge model are split into two components: the wind-driven one and the gradient one, while the component generated by in-     

Sulphate complexation in seawater: A relation between the stability constants of sodium sulphate and magnesium sulphate in seawater from a determination of the stability constant of hydrogen sulphate and a calculation of the single ion activity coefficient of sulphate

The conditional stability constant of HSO₄^? has been determined at 25°C, 1 atm and a formal ionic strength of 0.7 M in solutions containing sodium, magnesium, chloride and sulphate. This was done spectrophotometrically (UV), using diphenylamine as indicator. The value obtained was 17.0 ± 0.1 (molar scale). Single ion activity coefficients for Na₂SO₄, K₂SO₄ and MgSO₄ have been calculated according to the Bates et al. (1970) model, assuming that the sulphate ion is not hydrated. It was found that the single ion activity coefficient of sulphate changes very little between Na₂SO₄, K₂SO₄ and MgSO₄ when the formal ionic strength is kept constant.These results have been used to obtain relations between the stability constants of NaSO₄^? and MgSO₄ valid for seawater.     

The speciation of Fe(II) and Fe(III) in natural waters

The interactions of Fe(II) and Fe(III) with the inorganic anions of natural waters have been examined using the specific interaction and ion pairing models. The specific interaction model as formulated by Pitzer is used to examine the interactions of the major components (Na⁺, Mg²⁺, Ca²⁺, K⁺, Sr²⁺, Cl⁻, SO₄⁻, HCO₃⁻, Br⁻, CO₃²⁻, B(OH)₄⁻, B(OH)₃ and CO₂) of seawater and the ion pairing model is used to account for the strong interaction of Fe(II) and Fe(III) with major and minor ligands (Cl⁻, SO₄²⁻, OH⁻, HCO₃⁻, CO₃²⁻ and HS⁻) in the waters. The model can be used to estimate the activity and speciation of iron in natural waters as a function of composition (major sea salts) and ionic strength (0 to 3 M). The measured stability constants (K_FeX^*) of Fe(II) and Fe(III) have been used to estimate the thermodynamic constants (K_FeX) and the activity coefficient of iron complexes (γ_FeX) with a number of inorganic ligands in NaClO₄ medium at various ionic strengths: In(K_FeX/γ_Feγ_X) = InK_FeX − In(γ_FeX) The activity coefficients for free ions (γ_Fe, γ_x) needed for this extrapolation have been estimated from the Pitzer equations. The activity coefficients of the ion pairs have been used to determine Pitzer parameters (B_FeX, B_FeX⁰, C_FeX^φ) for the iron complexes. These results make it possible to estimate the stability constants for the formation of Fe(II) and Fe(III) complexes over a wide range of ionic strengths and in different media. The model has been used to determine the solubility of Fe(III) in seawater as a function of pH. The results are in good agreement with the measurements of Byrne and Kester and Kuma et al. When the formation of Fe organic complexes is considered, the solubility of Fe(III) in seawater is increased by about 25%.     

Sb2 Te3 纳米结构的制备与表征

以室温热电性能优异的传统热电材料Sb₂Te₃为研究对象,利用化学气相沉积法制备Sb₂Te₃单晶纳米结构,并研究其生长机理.实验结果表明,不加催化剂时Sb₂Te₃易生长成六方纳米盘,在金催化剂条件下定向生长成纳米线.Sb₂Te₃的形貌与其晶体结构和生长机理有关.Sb₂Te₃为三角结构,Sb和     

Monitoring of position of the Kuroshio axis in the Tokara Strait using sea level data

Properties of the index of position of the Kuroshio axis in the Tokara Strait, named the Kuroshio position index (KPI), were examined using sea-level data during 1984–92. The index is KPI=(X+M _x )/(Y+M _y whereX(Y) is the anomaly of sea-level difference of Nakanoshima (Naze) minus Nishinoomote from the 1984–92 meanM _x (M _y ). The correlation with the latitude of the Kuroshio axis in the Tokara Strait concluded that the KPI withM _x /M _y =0.83 and realisticM _y (100±40 cm) best indicates the position of the Kuroshio axis in the strait. The KPI withM _x =83 cm andM _y =100 cm was newly called the KPI as the best index. Using daily values of this KPI, the relation between the position of the Kuroshio in the strait and the large meander of the Kuroshio shown by Kawabe (1995) was confirmed and studied in detail. A large meander forms (ends) 3.3 (5.1) months after a northward (southward) shift of the Kuroshio in the Tokara Strait. Yet, a temporary southward shift with a duration of ten to twenty days does not finish the large-meander (LM) path. At the LM formation, a small meander southeast of Kyushu begins to move eastward associated with the northward shift. The processes of LM formation and decay are started by the meridional move of the Kuroshio axis in the Tokara Strait. The Kuroshio axis at the FES line during the LM path is located farther north by 7 latitude than that during the non-large-meander (NLM) path. The latitude during the LM formation (decay) stage is a little higher (lower) than that during the LM (NLM) period, though the Kuroshio still takes an NLM (LM) path.     

Reactive iron delivery to the Gulf of Alaska via a Kenai eddy

Mesoscale anticyclonic eddies in the Gulf of Alaska are an important mechanism for cross-shelf exchange of high iron, low nitrate coastal waters and low iron, high nitrate offshore waters. A Kenai eddy was sampled in September 2007, 8 months after formation. The subsurface eddy core layer contained reactive iron concentrations more than eight times greater than waters at the same depths outside the eddy. The subsurface core of the Kenai eddy (25.4≤σ_θ≤25.8) is suggested to be seasonally important as these waters can be brought to the surface with storm events and deep winter mixing. The deeper core layer (25.8≤σ_θ≤27.0) is suggested to be a source of iron to HNLC waters on a longer timescale, due to isopycnal mixing and eventual eddy relaxation. The subsurface and deeper core layers are important reservoirs of iron that can promote and sustain primary productivity over the lifetime of the Kenai eddy. In addition, dissolved and leachable particulate manganese are shown to be excellent tracers of eddy surface and subsurface waters, respectively.     

Temporal changes of soft-bottom zoobenthic communities in and around Alsancak Harbor (Izmir Bay, Aegean Sea), with special attention to the autecology of exotic species

Temporal and spatial variation in soft‐bottom benthic communities following recovery from a pollution episode were studied between January and September 2004 in and around Alsancak Harbor, located in the polluted part of Izmir Bay (Aegean Sea, eastern Mediterranean). Samples were collected at seven stations by van Veen grab. Three additional stations were sampled by means of a beam trawl to take into account large mobile animals and for a better estimate of the local biodiversity. A total of 231 species belonging to 10 zoobenthic groups were found. Polychaetes contributed 90% of the total faunal populations and mollusks 87% of the total biomass in the area. Community parameters varied significantly among stations and sampling periods; number of species ranged from 2 to 79 per 0.1 m² grab sample; density from 20 to 81,720 ind·m^?2; biomass from 0.1 to 4190 g·m^?2; Shannon–Wiener diversity index (log₂ base) from 0.4 to 4.4; and Pielou's evenness index from 0.11 to 1.0. Collections indicate that a number of species, including those sensitive to pollution, have colonized the area where azoic conditions had been previously reported. A total of six exotic species, Streblospio gynobranchiata, Polydora cornuta, Hydroides dianthus, Hydroides elegans, Anadara demiri and Fulvia fragilis, probably transferred to the area via ballast water or hull fouling, dominated soft or hard substrata in and near Alsancak Harbor. The first two species accounted for more than 70% of the total population in the area, while A. demiri contributed the most to the biomass (93%, at station 7).     

The beam attenuation to chlorophyll ratio: an optical index of phytoplankton physiology in the surface ocean?

The particulate beam attenuation coefficient (c_p) is proportional to the concentration of suspended particles in a size domain overlapping that of the phytoplankton assemblage. c_p is largely insensitive to changes in intracellular chlorophyll concentration, which varies with growth irradiance (a process termed ‘photoacclimation’). Earlier studies have shown that the ratio of c_p:chlorophyll (i.e., c_p^*) exhibits depth-dependent changes that are consistent with photoacclimation. Similar relationships may likewise be expected in the horizontal and temporal dimensions, reflecting changes in mixing depth, incident irradiance, and light attenuation. A link between c_p^* and more robust photoadaptive variables has never been explicitly tested in the field. Here we use five historical field data sets to directly compare spatial and temporal variability in c_p^* with two independent indices of photoacclimation: the light-saturated, chlorophyll-normalized photosynthetic rate, P^b_opt, and the light-saturation index, E_k. For the variety of oceanographic conditions considered, a first-order correlation emerged between c_p^* and P^b_opt or E_k. These simple empirical results suggest that a relationship exists between a bio-optical variable that can potentially be retrieved remotely (c_p^*) and physiological variables crucial for estimating primary productivity in the sea.