基于融合U-Net及ConvLSTM的海面高度异常预报方法研究

海面高度异常是反映海洋环境状况的主要变量之一。本文使用1993—2019年的融合月均海面高度异常数据,建立了基于深度学习的海面高度异常预测神经网络模型,提出了基于融合U型网络(U-Net)和卷积长短记忆网络(ConvLSTM)的中长期海面高度异常预报模型。在研究海域0.25°×0.25°的空间分辨率下,模型测试集预报结果的均方根误差和平均绝对误差分别为0.039 m和0.027 m,均优于全连接LSTM预报模型和ConvLSTM+CNN预报模型,为大中尺度的海面高度异常预报提供了新的方法。     

基于水准测量技术的填海人工岛沉陷监测实践

近年来随着填海人工岛的增多,其安全性备受关注.人工岛吹填区域软土地基物理力学参数差异大,地面沉陷持续时间长、成因机制复杂和防治难度大,沉陷监测工作具有重要意义.利用精密水准测量技术,通过长期跟踪监测,分析了人工岛吹填区域的变形特征,综合评估了沉降稳定性,为人工岛的环境保护、后续设计施工建设提供科学决策依据.     

Multi-step ahead short-term predictions of storm surge level using CNN and LSTM network

Storm surges pose significant danger and havoc to the coastal residents' safety, property, and lives, particularly at offshore locations with shallow water levels. Predictions of storm surges with hours of warning time are important for evacuation measures in low-lying regions and coastal management plans. In addition to experienced predictions and numerical models, artificial intelligence (AI) techniques are also being used widely for short-term storm surge prediction owing to their merits in good level of prediction accuracy and rapid computations. Convolutional neural network (CNN) and long short-term memory (LSTM) are two of the most important models among AI techniques. However, they have been scarcely utilised for surge level (SL) forecasting, and combinations of the two models are even rarer. This study applied CNN and LSTM both individually and in combination towards multi-step ahead short-term storm surge level prediction using observed SL and wind information. The architectures of the CNN, LSTM, and two sequential techniques of combining the models (LSTM–CNN and CNN–LSTM) were constructed via a trial-and-error approach and knowledge obtained from previous studies. As a case study, 11 a of hourly observed SL and wind data of the Xiuying Station, Hainan Province, China, were organised as inputs for training to verify the feasibility and superiority of the proposed models. The results show that CNN and LSTM had evident advantages over support vector regression (SVR) and multilayer perceptron (MLP), and the combined models outperformed the individual models (CNN and LSTM), mostly by 4％–6％. However, on comparing the model computed predictions during two severe typhoons that resulted in extreme storm surges, the accuracy was found to improve by over 10％ at all forecasting steps.     

桑沟湾不同形态锰的分布、季节变化及影响因素

利用催化动力学分光光度法和两步提取法对2011年4月（春）、8月（夏）、10月（秋）和2012年1月（冬）桑沟湾海域溶解态无机锰(DIMn)和表层沉积物中的锰的含量进行测定。结果表明,桑沟湾4个季节（春季至冬季,后同）DIMn浓度呈现出近岸高、远岸低的分布特点,其平均浓度分别为(60.5±43.1) nmol/L、(42.0±30.5) nmol/L、(23.4±11.2) nmol/L和(18.2±13.5) nmol/L,呈现出明显的季节变化,即春季最高,夏季、秋季次之,冬季最低;与相邻的俚岛湾和爱莲湾相比,桑沟湾春季、夏季DIMn的浓度较高,秋季、冬季则没有显著性差异。桑沟湾表层沉积物中总Mn在4个季节的含量分别为(861±308) mg/kg、(915±322) mg/kg、(589±108) mg/kg、(653±185) mg/kg,表层沉积物中醋酸提取态Mn在4个季节的含量分别为(500±272) mg/kg、(502±232) mg/kg、(322±81) mg/kg、(345±91) mg/kg,两者均表现出近岸高、远岸低的分布特点。醋酸提取态Mn的含量在春季、夏季要显著高于秋季、冬季。悬浮颗粒物的吸附和浮游生物的利用是影响桑沟湾DIMn浓度与分布的重要因素。桑沟湾DIMn的源主要包括河流及地下水输送、大气输送、沉积物−水界面释放;汇主要包括养殖生物的清除、向黄海的输送等。简单箱式模型收支计算结果显示,桑沟湾DIMn的源略大于汇,表明除了养殖生物的清除和向黄海的输送,桑沟湾DIMn还存在其他汇。本研究的结果为桑沟湾DIMn的生物地球化学循环的深入认识提供了基础数据。     

Levels and patterns of genetic variation in Pampus minor:Assessment of a mitochondrial DNA control region sequence

Pampus minor is an important commercial fish. Due to the similarity of external morphological characteristics among the genus Pampus species, P. minor has often been identified as the juvenile group of both P. cinereus and P. argenteus. While little genetic background on this species is known, this study was based on control region sequences and provided the first evaluation of the genetic signature of 264 individuals of P. minor from 11 populations along the coasts of China and Malaysia. The results indicate high genetic haplotype diversity and low nucleotide diversity in this species. Additionally, two differentiated haplotype lineages were identified in the P.minor populations. However, phylogenetic structures corresponding to the geographical locations were unable to be established. Analysis of molecular variance identified a vast majority of the genetic variation occurring within populations. F-statistic test value(FST) of pairwise indicated that great differences existed between the Chinese and Malaysian P. minor populations. For the Chinese populations, the genetic differences were insignificant with the exception of the Xiamen population, which is a marginal population. During the late Pleistocene, a population expansion of P. minor occurred. These expanded populations originated from the glacial refugium in the South China Sea and then rapidly occupied and adapted to their new habitat. The results of this study provide genetic information for ensuring the protection and management of P. minor resources.     

Using triple oxygen isotopes and oxygen-argon ratio to quantify ecosystem production in the mixed layer of northern South China Sea slope region

Quantifying the gross and net production is an essential component of carbon cycling and marine ecosystem studies.Triple oxygen isotope measurements and the O_2/Ar ratio are powerful indices in quantifying the gross primary production and net community production of the mixed layer zone,respectively.Although there is a substantial advantage in refining the gas exchange term and water column vertical mixing calibration,application of mixed layer depth history to the gas exchange term and its contribution to reducing indices error are unclear.Therefore,two cruises were conducted in the slope regions of the northern South China Sea in October 2014(autumn) and June 2015(spring).Discrete water samples at Station L07 in the upper 150 m depth were collected for the determination of δ~(17)0,δ~(18)O,and the O_2/Ar ratio of dissolved gases.Gross oxygen production(GOP) was estimated using the triple oxygen isotopes of the dissolved O_2,and net oxygen production(NOP) was calculated using O_2/Ar ratio and O_2 concentration.The vertical mixing effect in NOP was calibrated via a N_2O based approach.GOP for autumn and spring was(169±23) mmol/(m~2·d)(by O_2) and(189±26) mmol/(m~2·d)(by O_2),respectively.While NOP was 1.5 mmol/(m~2·d)(by O_2) in autumn and 8.2 mmol/(m~2·d)(by O_2) in spring.Application of mixed layer depth history in the gas flux parametrization reduced up to 9.5% error in the GOP and NOP estimations.A comparison with an independent O_2 budget calculation in the diel observation indicated a26% overestimation in the current GOP,likely due to the vertical mixing effect.Both GOP and NOP in June were higher than those in October.Potential explanations for this include the occurrence of an eddy process in June,which may have exerted a submesoscale upwelling at the sampling station,and also the markedly higher terrestrial impact in June.     

匹配层高频宽带水声换能器研究

为了获取更多的水下信息,提高声呐的探测和识别能力,设计高频宽带换能器是极为重要的。 匹配层技术是拓宽换能器带宽的有效方式。从理论上对匹配层拓宽换能器带宽的机理进行了分析,并利用数值计算和有限元仿真分析了匹配层对换能器性能的影响。结果表明：随着匹配层层数增加,换能器的谐振峰数目增加,峰与峰之间通过耦合能够实现拓宽带宽的效果。通过有限元仿真指导制成中心频率为 187.5 kHz 的双匹配层宽带换能器,其最大发送电压响应为 150.3 dB,–3 dB 带宽为 145 kHz。     

基于深度学习的三维自主避障技术研究

针对自主式潜航器航行中自主规避障碍物传统算法存在的障碍物区域探测精度低、障碍物识别不准确、潜航器航路不最优等问题,采用三维成像声呐和深度学习算法开展了自主规避障碍物优化技术研究, 并通过仿真和漳河水库试验测试了本算法的有效性,可有效提高航行器规避障碍物的成功率和精度,以及 AUV 航行路径优化。     

海水循环水系统中环境因子对大西洋鲑体内土腥味物质含量的影响

为获知不同时期封闭式海水循环水养殖系统中水质因子、浮游植物和细菌群落结构对大西洋鲑(Salmo salar)体内土腥味物质含量变化的影响,于2018—2019年4次采集封闭式海水循环水养殖系统的水样和大西洋鲑。测定水体的氨氮、亚硝氮、硝氮、活性磷酸盐等指标,分析水体浮游植物群落结构并通过16S高通量测序测定水体中细菌群落结构,通过微波蒸馏-固相微萃取-气相色谱-质谱联用(MD-SPME-GC-MS)方法,分析大西洋鲑背肌中土臭素(Geosmin,GSM)和二甲基异冰片(2-methylisoborneol,MIB)的含量。研究发现:测定水质指标中温度、溶解氧、盐度、pH、氨氮、亚硝氮、硝氮、活性磷酸盐、总氮、总磷、总悬浮物和溶解性总有机碳在不同时期差异显著。共鉴定出浮游植物7门、13目、26属,蓝藻门(Cyanophyta)、硅藻门(Bacillariophyta)和绿藻门(Chlorophyta)为优势门;不同时期细菌群落中的优势菌门均为变形菌门(Proteobacteria)和拟杆菌门(Bacteroidetes),但细菌群落结构存在差异,这主要是由水质差异引起的。在不同时期,鱼体MIB含量均高于GSM含量,MIB为鱼体中主要的土腥味物质,在7和10月MIB含量较高。鱼体土腥味物质含量受浮游植物和细菌群落影响,而水质因子可能通过影响浮游植物和细菌群落的结构,来影响养殖鱼体内土腥味物质的含量。     

南极长城站附近企鹅栖息地粪土沉积地层放射性核素210Pb定年

用γ谱方法测定了南极长城站附近特有生物群落栖息地沉积物中放射性核素含量,地表沉积物中40K,137Cs,210Pb,226Ra,228Ra,228Th.和238U平均比活度,分别为143,7.56,24.1,3.65,5.36,4.15和6.5Bq/kg.同时测试了阿德雷岛企鹅栖息地粪土沉积地层中放射性核素含量,利用其中的210Pb比活度,210Pb_ex垂向变化特征,推演沉积物的沉积速率和地质历史年代:其中AD1-a柱样时间跨度约为74a(1928~2002年),据此计算了沉积速率为0.063mm/a(r=0.794),并讨论了在南极特定条件下,放射性核素示踪对定年影响以及与区域现代气候环境变化的内在联系.