Estimation of Sea Ice Thickness from SARAL/AltiKa in Drifting Orbit Phase     

Purvee Joshi  Sandip R. Oza  Ujjwal K. Gupta  Shailendra Saini  D. Ram Rajak  I. M. Bahuguna 《Marine Geodesy》2020,43(3):302-323

Abstract

Intra and inter-annual variations in the sea ice thickness are highly sensitive indicators of climatic variations undergoing in the earth’s atmosphere and oceans. This paper describes the method of estimating sea ice thickness using radar waveforms data acquired by SARAL/Altika mission during its drifting orbit phase from July 2016 onwards yielding spatially dense data coverage. Based on statistical analysis of return echoes, classification of the surface has been carried out in three different types, viz. floe, lead and mixed. Time delay correction methods were suitably selected and implemented to make corrections in altimetric range measurements and thereby freeboard. By assuming hydrostatic equilibrium, freeboard data were converted into sea ice thickness. Results show that sea ice thickness varies from 4 to 5?m near ice shelves and 1 to 2.5?m in the marginal sea ice regions. Freeboard and sea ice thickness estimates were also validated using NASA’s Operation Ice Bridge (OIB) datasets. Freeboard measurements show very high correlation (0.97) having RMSE of 0.13. Overestimation of approximately 1–2?m observed in the sea ice thickness, which could be attributed to distance between AltiKa footprint and OIB locations. Moreover, sensitivity analysis shows that snow depth and snow density over sea ice play crucial role in the estimation of sea ice thickness.  相似文献   

PLS-ANN分析血浆自体荧光光谱的二阶导数光谱识别胃癌   总被引：1，自引：0，他引：1  

马君  朱玉平  毛伟征  李颖  史晓凤  郑荣儿  孟继武 《中国海洋大学学报(自然科学版)》2006,36(3):505-508

探讨偏最小二乘法结合神经网络法(简称PLS-ANN)分析血浆自体荧光光谱的二阶导数光谱识别胃癌的优势,对20例胃癌病人和23例健康人血浆进行以405nm为激发光的自体荧光光谱检测,采用PLS-ANN法分别对血浆自体荧光光谱和二阶导数光谱进行判别分析。PLS-ANN分析血浆的自体荧光光谱法诊断胃癌的灵敏度为75%,特异度为83%,准确率为79%,PLS-ANN分析血浆的二阶导数光谱法诊断胃癌的灵敏度为90%,特异度为96%,准确率为93%。结果表明PLS-ANN分析血浆的二阶导数光谱法识别胃癌,优于PLS-ANN分析血浆的自体荧光光谱法,有望成为快速识别胃癌的较理想方法。  相似文献   

中华绒螯蟹人工半咸水工厂化育苗试验研究报告   总被引：1，自引：0，他引：1  

刘连科  王洪芬 《海洋湖沼通报》1991,(3):80-83

在盐度为14—19‰的人工海水中,温度20—25℃条件下,189只平均体重100g的抱卵亲蟹产蚤状幼体4025万只。布苗密度为50—100万只/m~3为宜。必须经常换水,保持水质良好。人工饵料以单胞藻和丰年虫无节幼体为主,可适当加喂蛋黄。  相似文献   

Development of fouling communities on vertical structures in the Baltic Sea   总被引：6，自引：2，他引：6  

Susanne Qvarfordt  Hans Kautsky  Torleif Malm 《Estuarine, Coastal and Shelf Science》2006,67(4):618-628

The pillars of the bridge connecting the Island of Öland with the Swedish mainland were rebuilt between 1990 and 2000. The renovation produced pristine vertical concrete substrates, which became submerged in known years and seasons. The fouling communities on the pillars were examined in 2001 to determine whether the community structure could be explained in terms of either orderly successional development or of seasonal variation in the settlement of benthic organisms. As well, the communities on the pillars were compared to communities on the vertical surfaces of boulders in the area. The results indicated that an annual species composition is the final stage in the succession on the observed, vertical constructions. The few perennial species add to the variation between pillars as they increase in biomass (Polysiphonia fucoides) or become out-competed (Balanus improvisus). Also, observed seasonal differences in the biomass of these perennial species indicated that the time of year free space becomes available might be an important determinant of the future structure of the community. Comparison between the pillar and boulder communities showed that the artificial structures were not surrogates for the natural hard substrate: pillar communities differed in that they lacked most perennial algal species and had a high biomass of B. improvisus.  相似文献   

红海榄人工幼苗藤壶分布特征研究   总被引：4，自引：0，他引：4  

莫竹承  范航清  何斌源 《热带海洋学报》2003,22(1):50-54

调查了广西珍珠港人工红海榄幼苗叶片上藤壶分布的特征。结果显示,在一年生幼苗叶片上藤壶的空间分布格局总体上为聚集分布。分布型因海水盐度的变化而变化,在高潮盐度Sh<20.21的海水区域内,藤壶趋向于随机分布,反之则表现为聚集分布。大约在分点潮高潮位以下,平均每日潮水浸淹时间超过5.6h的潮滩上藤壶的危害明显加再,影响了红海榄幼苗的正常生长。  相似文献   

鮸鱼胚胎发育的研究   总被引：2，自引：0，他引：2  

徐镇  李明云  陈惠群 《海洋科学》2007,31(2):93-97

研究了人工繁殖时鮸鱼(Miichthys miiuy)胚胎的发育过程。鮸鱼受精卵呈圆球形,浮性,卵径为0.99~1.15 mm,中央大多具有1个油球,少数为2~3个或较多个油球。在水温为24.5~24.7℃,盐度为24的天然海水中,鮸鱼胚胎发育历时约21h 48 min孵化出膜。整个胚胎发育分为5个阶段,共21个发育期。  相似文献   

Prediction of Load Carrying Capacity of Corroded Reinforced Concrete Beam     

范颖芳  周晶冯新 《中国海洋工程》2004,18(1):107-118

A novel method for prediction of the load carrying capacity of a corroded reinforced concrete beam (CRCB) is presented in the paper. Nine reinforced concrete beams, which had been working in an aggressive environment for more than 10 years, were tested in the laboratory. Comprehensive tests, including flexural test, strength test for corroded concrete and rusty rebar, and pullout test for bond strength between concrete and rebar, were condueted. The flexural test results of CRCBs reveal that the distribution of surface cracks on the beams shows a fractal behavior. The relationship between the fractal dimensions and mechanical properties of CRCBs is then studied. A prediction model based on artificial neural network (ANN) is established by the use of the fractal dimension as the corrosion index, together with the basic intbrmation of the beam. The validity of the prediction model is demonstrated through the experimental data, and satisfactory resuits are achieved.  相似文献   

长竹蛏人工育苗技术的初步研究   总被引：4，自引：0，他引：4  

王云 《台湾海峡》2001,20(1):27-31

本文对长竹蛏繁殖习性、胚胎发育和人工育苗技术关键进行研究．结果表明亲贝经暂养可促进性成熟；幼虫对温、盐度的适应较广；变态附着采用缩光培育,未经缩光的附着时间延长,存活率降低;幼虫长至约240μm变态附着,附着量在(0.6～10)×106个/m  相似文献   

基于EMD与神经网络的机械故障诊断技术   总被引：2，自引：0，他引：2  

赵犁丰  周晨赓  仲京臣 《中国海洋大学学报(自然科学版)》2004,34(2):297-302

经验模式分解 (EMD)是分析非线性、非平稳信号的有力工具 ,它将信号分解为突出了原信号的不同时间尺度的局部特征信息的内在模函数 (IMF)分量。本文通过将各 IMF分量输入到 BP网络中进行训练学习和故障诊断 ,比直接输入原信号可以提高 BP网络对故障诊断的准确率 ,而且减少了训练时间。  相似文献   

The feasibility of escape mechanisms in conical snow crab traps     

Winger  Paul D.; Walsh  Philip J. 《ICES Journal of Marine Science》2007,64(8):1587-1591

  相似文献