Analysis of wave shoaling and shore-breakers on a low tide terrace beach based on in-situ measurements at Xisha Bay on South China coast

Low tide terrace beach is a main beach type along South China coasts with strong tidal actions.How strong tides affect wave transformations on low tide terrace beach still remains unclear.In this study,in-situ measurements are conducted on the low terrace beach at Xisha Bay to provide quantitative descriptions of wave shoaling and shore-breaker phenomena under the tidal effects.It is found that wave breaking is unsaturated on the low tide terrace beach at Xisha Bay.Magnitudes of wave skewness and asymmetry increase as wave shoals and achieve the maximum value at the shore-breaker,and then decrease rapidly.Mean energy dissipation rates of shore-breakers are tide-modulated since the bottom slope changes at the shoreward boundary of wave propagation in a tidal cycle.The remaining wave energy flux at the initialization of the shore-breaker is 1%–12%of offshore wave energy flux,and the energy flux ratio decreases with increasing offshore wave heights.Wave attenuation at shore-breakers can be estimated directly from offshore wave conditions based on findings in this study,favoring designs of seawalls or beach nourishment projects.Field datasets on wave transformations can also be used for verifications of wave numerical models.

Thermodynamics and Microphysical Characteristics of an Extreme Rainfall Event Under the Influence of a Low-level Jet over the South China Coast

In this paper,the data of Automatic Weather Stations(AWSs),ERA5 reanalysis,sounding,wind profile radar,and dual-polarization radar are used to study an extreme rainfall event in the south China Coast on 11 to 12 May 2022 from the aspects of thermodynamics and microphysical characteristics under the influence of low-level jets(LLJs).Results show that:(1)The extreme rainfall event can be divided into two stages:the first stage(S1)from 0000 to 0600 LST on May 12 and the second stage(S2)from 0700 to 1700 LST on the same day.During S1,the rainfall is mainly caused by the upper-level shortwave trough and the boundary layer jet(BLJ),characterized by strong upward motion on the windward side of mountains.In S2,the combined influence of the BLJ and synoptic-system-related low-level jet(SLLJ)increases the vertical wind shear and vertical vorticity,strengthening the rainstorm.In combination with the effect of topography,a warm and humid southwest flow continuously transports water vapor to farther north,resulting in a significant increase in rainfall over the study area(on the terrain’s windward slope).From S1 to S2,the altitude of a divergence center in the upper air decreases obviously.(2)The rainfalls in the two stages are both associated with the mesoscale convergence line(MCL)on the surface,and the wind field from the mesoscale outflow boundary(MOB)in S1 is in the same direction as the environmental winds.Due to a small area of convergence that is left behind the MOB,convection moves eastward quickly and causes a short duration of heavy rainfall.In S2,the convergence along the MOB is enhanced,which strengthens the rainfall and leads to strong outflows,further enhancing the surface convergence near the MOB and forming a positive feedback mechanism.It results in a slow motion of convection and a long duration of heavy rainfall.(3)In terms of microphysics,the center of a strong echo in S1 is higher than in S2.The warm-rain process of the oceanic type characterizes both stages,but the convective intensity in S2 is significantly stronger than that in S1,featuring bigger drop sizes and lower concentrations.It is mainly due to the strengthening of LLJs,which makes small cloud droplets lift to melting levels,enhancing the ice phase process(riming process),producing large amounts of graupel particles and enhancing the melting and collision processes as they fall,resulting in the increase of liquid water content(LWC)and the formation of large raindrops near the surface.

Preliminary research on sea-level changes of the South China coast since late Epipleistocene

Several views on sea-level changes of the South China coast are briefly introduced in this paper. On the basis of 236 samples whose ages are determined by 14C chronological method and their sites are corrected with ancient water depth and crustal deformation, a basic model about sea-level changes of the South China coast since late Epipleistocene is set up. This model basically accords with the general cognitions of predecessors, i. e. it not only represents the common characteristics of sea-level changes of the East China coast but has some features of the South China coast itself. In general, this model is relatively close to the Fairbridge's curve, indicating that the sea-level undulations exist since 6 ka ago but the ranges of undulations are slightly larger than those of Fairbridge's curve.

Coastal dune rock development and Holocene climate changes in South China

Coastal dune rocks in China are eolian sands cemented by calcium carbonate under subaerial conditions, widely distributing on the tropical and subtropical coasts of South China. Particular temperature and precipitation as well as local wave and landform conditions are required for the formation of the dune rocks. A correspondence was found between Holocene environmental changes and coastal dune rock development by comparing the features of the sea-level and climate changes in the Holocene period with the ages, scales, and cementation of the dune rocks on the South China coasts. The findings provide well grounded explanation for some problems unresolved in the past researches on the coastal dune rock in South China： （1） There were no dune rocks with ages older than 6000 years in South China because the dune rocks formed before 6000 a BP were covered by the sea water that rose in the later period; （2） the dune rocks with ages of around 3000 a BP were widely found in South China today because the coastal dunes were cumulated on a large scale at that time as a result of temperature falling after the end of Megathermal; （3） Medieval Warm Period was the main period for the eolian dunes to be cemented into the coastal dune rocks in South China; （4） lack of dune rocks of younger than 1000 a BP was accounted for by that the climate conditions in recent one thousand years were not suitable for the cementation.

A study on Holocene aeolian shell-clastic sandstonesalong the coasts of South China andthe analysis of its formation

The Holocene aeolian shell-clastic sandstones at 13 places along the coasts of Fujian, Guangdong and Hainan Provinces are studied in the following respects; describing their features from both macroscopic and microscopic views, listing their distributions, altitudes and forming ages, and discussing the nomenclatures of this kind of rock and its differences from beach rock.

海洋空间的“领土化”构建与实践 ——以美国在南海地区的干涉行动为例

随着海洋与人类的联系越来越密切,控制人类海上活动的必要性,令海洋空间的“领土化”成为难以避免的趋势。主流话语开始从将海洋描述为无主之地,变成倾向于为扩大公共权力对海域控制的做法辩护,为海上力量投送和海域管控编织正当理由。由此,产生了一定的海洋空间“领土化”,国家从规范功能的角度逐渐控制海洋空间,将公共权力投射至领海和管辖水域外的海域。塑造符合自身利益需求的地区规范秩序,并在实践上强化地区军事力量投送,这两种海洋空间“领土化”扩张方式,鲜明地体现在美国在南海地区的干涉行动中。中国需在南海促进建设更有效的海洋治理体系,扩大行为规范塑造和海洋新秩序建设上的话语权,更好地维护国家海洋安全和发展利益。

Temperature variability caused by internal tides in the coastal waters of east coast of Peninsular Malaysia

The effects of tidal currents(i.e., barotropic and internal tides) are important in the biogeochemistry of a coastal shelf sea. The high-frequency of currents and near-bottom temperatures collected in three consecutive southwest monsoon seasons(May, June, July and August of 2013 until 2015) is presented to reveal the role of the tidal currents to the temperature variability in the coastal shelf sea of the east coast of Peninsular Malaysia(ECPM),south of the South China Sea(SCS). The results of a spectral density and harmonic analysis demonstrate that the near-bottom temperature variability and the tidal currents are influenced by diurnal(O_1 and K_1) and semidiurnal(M_2) tidal currents. The spectral density of residual currents(detided data) at 5, 10 and 16 m depth also shows significant peaks at the diurnal tidal frequency(K_1) and small peaks at the semidiurnal tidal frequency(M_2)indicating the existence of internal tides. The result of the horizontal kinetic energy(HKE) shows a strong intermittent energy of internal tides in the ECPM with the strongest energy is found at 16 m depth during a sporadic cooling event in June and July. A high horizontal cross-shore heat flux(16 m) also indicates strong intrusions of cooler water into the ECPM in June and July. During the short duration of cold pulse water observed in June and July, a cross-wavelet analysis also reveals the strong relationship between the near-bottom temperatures and the internal tidal currents at the diurnal tidal frequency. The intrusion of this cooler water is probably related to the monsoon-induced upwelling in June. It is loosely interpreted that the interaction between the strong barotropic tides and the steep slope in the central basin of the SCS under the stratified condition in southwest monsoon has generated these internal tides. The dissipation of internal tides from the slope area probably has driven the cold-upwelled water into the ECPM coastal shelf sea when the upwelling intensity is the highest in June and July.

华南沿海海草床分布区大型底栖动物群落特征初探

为探究华南沿海海草床大型底栖动物群落特征、地区差异及其与海草群落间的关系,2020年在华南沿海12个海草床区域开展了大型底栖动物调查。共布设33个调查断面99个站位,在主要群落参数的基础上,运用相关性分析和聚类分析、nMDS排序、相似性百分比分析等群落生态学统计方法分析了底栖动物群落特征及其与海草群落的关系。共鉴定出大型底栖动物9大门类199种,其中,软体动物种类最多,占总种类数的39.7%。各区域底栖动物的平均栖息密度为155.7 ind/m2,青葛—龙湾(琼海)的平均栖息密度最低,珍珠湾(防城港)的平均栖息密度最高;平均生物量为118.36 g/m2,最低值出现在义丰溪(汕头),最高值出现在珍珠湾。各区域底栖动物的优势种以潮间带泥沙滩常见腹足类、双壳类和多毛类为主;底栖动物的种类多样性指数(H′)平均值为1.12,最低值出现在唐家湾(珠海),最高值出现在铁山港(北海);各调查区域底栖动物主要群落参数大致呈现“北部湾>海南沿岸>珠江口及粤东”的规律。华南沿海海草床分布区大型底栖动物群落的区域性特征较为明显,地理位置相近的海草床底栖动物群落特征相似性程度较高。海草密度越大,总生物量越高,越有利于底栖动物的种类多样性指数维持在更高水平。以大、中型海草为主的海草床,相较于面积小,以小型海草为主的海草床,其区域内的大型底栖动物群落结构更为复杂。

红树林生长带与潮汐水位关系的研究

根据海南东寨港林市村、廉江车扳镇那腮村、深圳锦绣中华等3个实验点10条横断面红树林潮滩高程水准测量，林市村潮汐水位观测，潮汐特征水位及浸淹频率分布计算，参照有关港点潮汐实例或预报资料，确定红树林外边界为平均海面或稍上，内边界（或林内最大高程）为回归期平均高高潮位（或大潮平均高潮位）。对国内外有关报道进行了评述。指出国内许多红树林文献中使用的“高潮位”、“中潮位”、“低潮位”用潮汐学术语表述应为“回归潮（或大潮）高潮位”、“中期高潮位”、“分点期（或小潮）高潮位”。明确红树林生长带位于平均海面以上的潮滩，对红树林建立和演替的研究，红树林宜林地选择及用红树林泥炭研究海平面变化均有重要意义。

2000年来华南沿海气候与环境变化

通过华南沿海两个钻孔剖面的孢粉分析，并用14种热带、南亚热带木本植物花粉含量之和与5种中、北亚热带和暖温带木本植物花粉含量之和的比值作为冷热变化的温度半定量曲线；利用2000年来古籍、地方志记载的典型热带动、植物分布、兴衰的变化作冷暖变化事件；以华南沿海罕见的降雪记载，特别是对15世纪以来的降雪现象分纬度统计其出现频率，探讨华南的小冰期。据此分析华南沿海2000年来的气候和环境变化。

华南海岸沙丘岩形成与全新世环境变化的关系

海岸沙丘岩是热带亚热带地区由碳酸盐胶结的海岸风成堆积,其成岩过程的各个阶段需要特定的水热和地貌条件。对华南海岸沙丘岩的形成年代、堆积高度、出露地点进行统计分析,将其特征与全新世环境变化事件作对比,结果显示华南沿海沙丘岩的形成过程与全新世气候变化及海平面变化等事件有很好的对应关系,能很好地解释我国沙丘岩研究中一些尚未解决的问题:华南沿海缺少5000aBP以前沙丘岩是因为当时的沙丘岩形成于低海面,后来因海面上升而被淹没;3000aBP前后海岸风沙大规模堆积是大暖期结束后气温下降的结果;华南沿海沙丘岩的胶结主要发生在中世纪暖期;华南沿海缺少年代小于1000aBP沙丘岩是因为近千年来气候条件下,不适合沙丘岩的胶结。

华南砂质海滩的动力地貌分析

为探讨华南砂质海滩的动力地貌学特征,对不同地理岸段不同地貌形态的8 个沙滩剖面于冬、夏季进行现场重复调查和室内分析工作.据此,通过对华南海岸带地质构造、地貌和现代海岸动力环境地域变化的分析,将华南沿海砂质海岸划分为岬湾岸、沙坝潟湖岸和夷直岸三种基本海岸地貌类型,并且从滩面倾向、海岸动力环境影响、季节冲淤变化趋势和滩面沉积物粒径、坡度的动力响应等方面探讨砂质海滩的动力地貌,得出其受制于多种环境因素的影响,其中地质构造背景和海平面变化为大尺度的砂质海岸地貌的发育奠定了基础,而全新世海侵海平面相对稳定后,海岸动力条件的塑造起着决定性的影响,浪潮作用指数是其中重要的影响指标.

华南沿海近100年来2月份的极端气温事件

采用IPCC AR4规定的极端天气事件划分标准，分析1908—2008年广州、香港、澳门和澎湖气象站2月份平均气温序列的变化趋势、极端冷／暖月的时空变化及其与伞球气候变暖的关系，得出近100a来华南沿海2月份各站平均气温存在准同步性和0．7-1．6℃／100a的上升趋势；其间还存在7个极端冷月和6个极端暖月。极端最冷、最暖月分别为1945年2月和2007年2月。受全球气候变暖的影响，近10a来2月份极端气候事件发生频率呈增大趋势，约2～3a1次。

1960―2013年华南沿海海洋站SST变化及其影响因子

根据1960―2013年华南沿海7个海洋站的实测海表温度（SST）及全球平均表面温度、太平洋年代际涛动（PDO）、ENSO、南海高压、华南沿海近海面风速等资料,采用线性回归、Yamamoto突变检验、小波分析、相关分析等方法,研究了近54 a华南沿海SST时空变化及其影响因子,结果表明：1）近54 a华南沿海的年平均SST呈准同步变化和显著增暖趋势,其气候倾向率为0.08~0.17℃/10 a,平均为0.12℃/10 a,以冬季增暖最为显著;2）SST变化在1997/1998年出现突变现象;3）SST变化有多时空尺度的变化特征,其中最显著的变化周期是2~4 a的年际变化;4）SST变化深受ENSO事件的影响,约滞后于MEI指数2~4个月;5）影响SST变化趋势的主要因子有全球气候变暖、PDO、南海高压、华南沿海近海面层风速等。

华南沿海若干砂质海滩沉积物粒度特征的分析

根据2003年7月在华南沿海12个砂质海滩所取得的76个沉积物样品(其中次表层样品36个,不计入研究范围),就该区的沉积物粒度特征展开论述。为了便于分析其沉积物粒度特征,我们把华南沿海12条海滩剖面根据岸滩形态和成因将华南砂质海岸划分为岬湾型砂质海岸、沙坝-潟湖型砂质海岸和夷直型砂质海岸三大类。阐述了不同类型海滩的表层沉积物的粒度特征、类型、分布以及粒度的沿程变化特征。

华南沿海地质灾害类型、发育规律和防治对策

本文系统和全面地论述华南沿海地质灾害的类型和发育规律。从宏观控制因素划分出岩石圈、大气圈、水圈及生物圈控制的四大地质灾害类型,阐明各类型发灾特点,论述主要地质灾害类型的分布和发育规律,提出灾害的总体防治对策。

华南大陆沿岸珊瑚礁的特点与分析

华南大陆沿岸不乏造礁石珊瑚生长,但能成礁的仅在西部广西涠洲岛、斜阳岛和广东雷州半岛西南海岸,均为岸礁,累计礁体长约63 km,约占华南大陆（含近岸岛屿）岸线的1%,礁厚1-4 m,总面积约45 km^2。礁体在全新世中期形成,胶结程度差,内礁坪部分已被沿岸泥沙覆盖,活珊瑚种类较少。进入全新世晚期,环境条件发生变化,冬季表层平均水温略低,沿岸泥沙运动活跃,人类生产活动对水质的影响等,珊瑚礁发育受到制约。但在西部海岸局部地方造礁珊瑚仍然顽强地生长,礁体向海拓展。预测未来冬季水温升高,更有利于珊瑚礁自然恢复。

华南沿海牡蛎重金属含量特征及其风险评估

根据2009年对华南沿海部分海域的近江牡蛎和太平洋牡蛎的监测数据,对产品中重金属元素Cd、Cu、Pb、As、Hg和Zn的含量水平、分布与变化特征进行了分析讨论;采用点评估方法,计算Cd、Cu、Pb、As、Hg和Zn的膳食暴露量,对牡蛎产品的食用安全性进行风险评估。结果表明,调查海域牡蛎样品中Cu、Zn、Cd的含量较高,其值分别为92.0、268、1.32 mg/kg(湿重,下同);Hg、As、Pb的含量低,其值分别为9.21、0.11、0.26 mg/kg。不同海域、不同养殖季节的牡蛎产品中重金属元素的含量具有明显的差异。与无公害水产品质量标准的限量值相比,调查海域牡蛎产品中Cu、Zn、Pb、Hg、As的含量符合产品质量标准,Cd的含量超过产品限量标准值。由于元素间的相互作用,牡蛎产品Zn的含量高、Cd的含量低,Zn的可利用性阻止对Cd的吸收,牡蛎产品中的Cd不会对健康造成危害。风险评估的结果显示,每周食用适量的牡蛎,重金属的膳食摄入量低于世界卫生组织/联合国粮食和农业组织的食品添加剂联合专家委员会(JECFA)推荐的暂定每周耐受摄入量,处于安全范围内。

华南沿海温泉成因探讨

首先分析了华南沿海温泉成因 ,排除该区多数温泉具局部衰变热、岩浆残余热、断层活动热成因的可能性。重点讨论了地下水深特循环的动力学模型 ,分析了地下水循环深度 (相当于张性断层的规模 )和水头压力(相当于地形反差 )对泉温和流量的控制作用 ,并把泉温和流量与理论计算曲线对比 ,从而得出华南温泉为深循环的成因的结论。分析还得出 ,较大地形反差和张性大断裂是温泉形成的两个有利条件 ,如果仅具备其中一个条件 ,那么张性大断裂 (小地形反差 )比大地形反差 (小断裂 )更有利于获得较高泉温。可见 ,温泉深循环的动力学模型对华南沿海地热资源的预测、开发和利用有一定的指导意义。最后 。

华南海岸现代沙丘沙与海滩沙粒度的定量识别

海岸沙丘沙和海滩沙的粒度识别与区分是海岸风沙研究中争论较大的问题之一。以我国华南海岸为研究区域,基于在海岸风沙地貌广泛发育的闽南、粤东、粤西、海南岛沿岸4个区域的141个现代海岸沙丘沙和70个海滩沙样品的粒度数据,尝试运用多元线性判别分析和人工神经网络分析两种方法进行现代沙丘沙和海滩沙粒度的定量识别。结果表明,比较而言非线性的人工神经网络分析法较传统线性判别分析方法的识别率为高,人工神经网络分析可以通过粒度数据区分部分海岸的沙丘沙和海滩沙,但整体而言2种定量识别方法均难以完全对华南海岸的现代沙丘沙和海滩沙进行粒度的有效区分。