长江口南汇湿地植被的光谱吸收特征研究   总被引：1，自引：0，他引：1       下载免费PDF全文

张雪薇  韩震  刘美君  丁如一 《海洋学研究》2018,36(2):50-54

植被的光谱吸收特征与植被生长状况密切相关,同时也受土壤湿度等外界因素影响。本文以长江口南汇湿地典型植被芦苇、互花米草和海三棱藨草为研究对象,在计算其光谱特征参数的基础上,分析了这3种植被的光谱吸收特征形变PSDI值。最后结合实测的土壤湿度,分析了3种植被的PSDI值和土壤湿度的相关性。研究结果发现:互花米草的PSDI值最大,海三棱藨草的PSDI值最小,芦苇介于两者之间,表明互花米草受外界的环境影响较大;互花米草的PSDI值与土壤湿度的相关性最大,芦苇的PSDI值与土壤湿度的相关性最小,海三棱藨草介于两者之间,表明互花米草适应湿地环境能力较强。  相似文献   

SWAN模型对实验室小尺度浅水波浪模拟研究     

时莹  梁书秀  孙昭晨 《海洋工程》2018,36(6):116-123

基于浅水斜坡地形的物理模型试验数据,考察SWAN模型对实验室小尺度浅水波浪的模拟效果,进而检验其浅水项的模拟精度。模拟中采用直接输入初始测点的实测海浪谱进行造波,重点考察浅水中三波相互作用和变浅破碎两个源项,对不同工况下,SWAN模式在水深条件变化下的有效波高、谱平均周期、海浪谱演化的模拟能力进行研究。研究表明:模拟的有效波高较符合实测波浪的增长和衰减,但谱平均周期计算值明显偏小;海浪谱的能量转移机制同实测有较大区别,频谱模拟结果出现高频高估、低频低估现象。对两个源项进行对比分析得出三波相互作用对海浪谱的能量转换影响远大于变浅破碎耗散。想要提高近岸区谱平均周期和海浪谱的模拟精度则SWAN模型中三波非线性项的计算精确度仍需更多研究和改进。  相似文献   

开孔率对明基床上开孔沉箱波浪反射系数影响的数值研究     

蔡郁  孙大鹏  赵沛泓  吴浩 《海洋工程》2018,36(5):30-37

开孔率是开孔沉箱波浪反射系数的重要影响因素,迄今为止关于开孔沉箱的物模试验研究成果(包括《防波堤设计与施工规范》)中,开孔率μ通常以线性关系反映在开孔沉箱波浪反射系数的计算关系式中,适用范围为0.2~0.4。但当μ0.2或μ0.4时,开孔率μ对波浪反射系数Kr的影响规律尚需进一步的研究探讨。现借助二维数值波浪水槽,在扩大了的开孔率取值范围内,模拟不规则波与可渗明基床上开孔沉箱的相互作用。结果表明:在0.2≤μ≤0.4的范围内,用线性关系描述开孔率μ对波浪反射系数Kr的影响是合适的;在μ0.4时,数模值和物模试验拟合的经验关系式的趋势是一致的;在μ0.2时,开孔沉箱反射系数K_r随开孔率μ的减小而增大,用物模试验拟合的经验关系式及《防波堤设计与施工规范》中计算公式的线性关系来描述开孔率μ对反射系数K_r的影响是不恰当的。研究成果对开孔沉箱消浪机理的深入认识和开孔沉箱结构的优化设计具有重要意义。  相似文献   

滕州荆泉水源地岩溶塌陷特征与成因分析          下载免费PDF全文

贾继成  孟宪洲  白平 《山东国土资源》2018,34(6)

自2015年6月以来,在山东滕州荆泉水源地范围内连续发生多起岩溶塌陷。通过研究区域地质条件,在已有认识的基础上分析得出发育的浅层开口岩溶洞隙的存在,一定厚度的松散覆盖层及地下水位大幅下降是该区产生岩溶塌陷的基本条件。阐述了岩溶塌陷形成发育过程及影响因素,得出长期过量抽采岩溶水是区内岩溶塌陷的主要因素,合理减少地下水开采量是预防岩溶塌陷最有效的方法。  相似文献   

A 10-year wave energy resource assessment and trends of Indonesia based on satellite observations     

Amiruddin  Ribal Agustinus  Khaeruddin  Thamrin Sri Astuti 《海洋学报(英文版)》2019,38(8):86-93

Wave energy resource assessment and trends around Indonesian's ocean has been carried out by means of analyzing satellite observations. Wave energy flux or wave power can be approximated using parameterized sea states derived from satellite data. Unfortunately, only some surface parameters can be measured from remote sensing satellites, for example for ocean surface waves: significant wave height. Others, like peak wave period and energy period are not available, but can instead be estimated using empirical models. The results have been assessed by meteorological season. The assessment shows clearly where and when the wave power resource is promising around Indonesian's ocean. The most striking result was found from June to August, in which about 30–40 kW/m(the 90 th percentile: 40–60 kW/m, the 99th percentile: 50–70 kW/m) wave power energy on average has been found around south of the Java Island. The significant trends of wave energy at the 95% level have also been studied and it is found that the trends only occurred for the extreme cases, which is the 99th percentile(i.e.,highest 1%). Wave power energy could increase up to 150 W/m per year. The significant wave heights and wave power have been compared with the results obtained from global wave model hindcast carried out by wave model WAVEWATCH III. The comparisons indicated excellent agreements.  相似文献   

Alteration of hydrological processes and streamflow with juniper (Juniperus virginiana) encroachment in a mesic grassland catchment          下载免费PDF全文

Chris B. Zou  Donald J. Turton  Rodney E. Will  David M. Engle  Sam D. Fuhlendorf 《水文研究》2014,28(26):6173-6182

To understand the effect of woody plant encroachment on hydrological processes of mesic grasslands, we quantified infiltration capacity in situ, the temporal changes in soil water storage, and streamflow of a grassland catchment and a catchment heavily encroached by juniper (Juniperus virginiana, eastern redcedar) in previously cultivated, non‐karst substrate grasslands in north‐central Oklahoma for 3 years. The initial and steady‐state infiltration rates under the juniper canopy were nearly triple to that of the grassland catchment and were intermediate in the intercanopy spaces within the encroached catchment. Soil water content and soil water storage on the encroached catchment were generally lower than on the grassland catchment, especially when preceding the seasons of peak rainfall in spring and fall. Frequency and magnitude of streamflow events were reduced in the encroached catchment. Annual runoff coefficients for the encroached catchment averaged 2.1%, in contrast to 10.6% for the grassland catchment. Annual streamflow duration ranged from 80 to 250 h for the encroached catchment compared with 600 to 800 h for the grassland catchment. Our results showed that the encroachment of juniper into previously cultivated mesic grasslands fundamentally alters catchment hydrological function. Rapid transformation of mesic grassland to a woodland state with juniper encroachment, if not confined, has the potential to drastically reduce soil water, streamflow and flow duration of ephemeral streams in the Southern Great Plains. Copyright © 2013 John Wiley & Sons, Ltd.  相似文献   

Rare earth elements and yttrium in ferromanganese deposits from the South China Sea: distribution, composition and resource considerations     

ZHONG Yi  CHEN Zhong  GONZALEZ Francisco Javier  ZHENG Xufeng  LI Gang  LUO Yun  MO Aibin  XU Antao  WANG Shuhong 《海洋学报(英文版)》2018,37(7):41-54

Ferromanganese nodules and crusts contain relatively high concentration of rare earth elements(REE) and yttrium(REY),with a growing interest in exploitation as an alternative to land-based REY resources.On the basis of comprehensive geochemical approach,the abundance and distribution of REY in the ferromanganese nodules from the South China Sea are analyzed.The results indicate that the REY contents in ferromanganese deposits show a clear geographic regularity.Total REY contents range from 69.1×10~(–6) to 2 919.4×10~(–6),with an average value of 1 459.5×10~(–6).Especially,the enrichment rate of Ce content is high,accounting for almost 60% of the total REY.This REE enrichment is controlled mainly by the sorption of ferromanganese oxides and clay minerals in the nodules and crusts.Moreover,the total REY are higher in ferromanganese deposits of hydrogenous origin than of diagenetic origin.Finally,Light REE(LREE) and heavy REE(HREE) oxides of the ferromanganese deposits in the study area can be classified into four grades: non-enriched type,weakly enriched type,enriched type,and extremely enriched type.According to the classification criteria of rare earth resources,the Xisha and Zhongsha platform-central deep basin areas show a great potential for these rare earth metals.  相似文献   

The exponential decline in saturated hydraulic conductivity with depth: a novel method for exploring its effect on water flow paths and transit time distribution          下载免费PDF全文

A. A. Ameli  J. J. McDonnell  K. Bishop 《水文研究》2016,30(14):2438-2450

The strong vertical gradient in soil and subsoil saturated hydraulic conductivity is characteristic feature of the hydrology of catchments. Despite the potential importance of these strong gradients, they have proven difficult to model using robust physically based schemes. This has hampered the testing of hypotheses about the implications of such vertical gradients for subsurface flow paths, residence times and transit time distribution. Here we present a general semi‐analytical solution for the simulation of 2D steady‐state saturated‐unsaturated flow in hillslopes with saturated hydraulic conductivity that declines exponentially with depth. The grid‐free solution satisfies mass balance exactly over the entire saturated and unsaturated zones. The new method provides continuous solutions for head, flow and velocity in both saturated and unsaturated zones without any interpolation process as is common in discrete numerical schemes. This solution efficiently generates flow pathlines and transit time distributions in hillslopes with the assumption of depth‐varying saturated hydraulic conductivity. The model outputs reveal the pronounced effect that changing the strength of the exponential decline in saturated hydraulic conductivity has on the flow pathlines, residence time and transit time distribution. This new steady‐state model may be useful to others for posing hypotheses about how different depth functions for hydraulic conductivity influence catchment hydrological response. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

海州湾4种鱼类生长特征的空间异质性     

王琨  张崇良  王晶  任一平 《海洋学报》2019,41(12):62-70

传统的渔业资源评估均假设鱼类的生长参数是匀质的，然而近年来越来越多的研究表明海洋鱼类生长存在空间异质性。为探究海州湾鱼类生长参数的空间异质性现象，本研究分析了2013–2018年海州湾及其邻近海域方氏云鳚(Pholis fangi)、尖海龙(Syngnatus acus)、小黄鱼(Larimichthys polyactis)和赤鼻棱鳀(Thryssa kammalensis)的空间分布，使用电子体长频率分析方法结合Bootstrap重抽样方法估算了这4种鱼类的生长参数及其在深、浅水区域中的差异。结果显示，这4种鱼类生长参数均表现出一定的空间异质性，其中尖海龙和小黄鱼生长参数的空间异质性表现较为明显。这种差异可能是由于空间上的理化条件、群落结构以及物种本身洄游分布的差异而产生的。  相似文献   

海南典型热带海草床4种代表性鱼类的生长特征及其对海草资源量变化的响应     

陈启明  刘松林  张弛  崔黎军  江志坚  吴云超  黄小平 《热带海洋学报》2020,39(5):62-70

文章以海南岛新村湾、黎安港和潭门港海草床为研究区域, 选取褐篮子鱼(Siganus fuscessens)、点斑篮子鱼(Siganus guttatus)、四带牙鯻(Pelates quadrilineatus)和细鳞鯻(Terapon jarbua) 4种代表性鱼类为研究对象, 分析其体长与体质量的关系, 并探讨4种鱼类对海草资源量变化的响应。结果表明, 除栖息于潭门港海草床的4种鱼为负异速生长, 其他区域海草床的鱼类均为正异速或等速生长; 4种鱼的体质量生长速率(即异速生长因子b)和肥满度呈现黎安港>新村湾>潭门港的趋势, 并与3个海草床的海草覆盖率、密度和生物量的变化趋势一致; 推测海草资源量下降可能增加鱼类的被捕食压力和减少食物来源, 从而导致生活于海草床的代表性鱼类生长速率下降。  相似文献