基于F-范数的不确定性平差模型的解算方法     

鲁铁定  朱国红 《大地测量与地球动力学》2018,38(6):557-561

为提高基于F-范数的不确定性平差模型的解算效率，给出直接迭代算法进行参数估计。该算法无需SVD，解算过程简单且易于编程计算，同时给出迭代不收敛时的SVD-解方程算法。二元线性拟合及沉降观测AR模型的算例结果表明，这2种算法正确可行，与SVD-迭代算法具有等价性。当迭代收敛时，宜使用直接迭代算法，收敛速度更快，解算效率更高；当迭代不收敛时，可釆用SVD-解方程算法。  相似文献   

Study of irregular wave run-up over fringing reefs based on a shock-capturing Boussinesq model     

《Applied Ocean Research》2019

This paper presents the results of a parametric study of irregular wave run-up over fringing reefs using the shock-capturing Boussinesq wave model Funwave-TVD to better understand the role of fringing reefs in the mitigation of wave-driven flooding. Laboratory experiments were newly performed with a typical fringing reef profile and typical hydrodynamic conditions to validate the model. Experimental data shows irregular wave run-ups are dominated by the low-frequency motions and confirms the run-up resonant phenomenon over the back-reef slope, which has been revealed in previous numerical studies. It is demonstrated that irregular wave evolution and run-up over fringing reefs are reasonably reproduced by the present model with a proper grid size. However, the infragravity run-up height and highest 2% run-up height over the back-reef slope are under-predicted due to the underestimation of the infragravity wave height over the reef flat. The validated model was then utilized to model irregular wave transformations and run-ups under different conditions. Through a series of numerical experiments, the effects of key hydrodynamic and reef geometry parameters, including the reef flat width, water depth over the reef flat, fore-reef slope angle and back-reef slope angle, on the irregular wave run-up were investigated. Variations of spectral components of irregular wave run-ups were examined to better understand the physical process underlying the effect of each parameter.  相似文献   

全球气候变化下南海诸岛保护优先区识别分析   总被引：3，自引：1，他引：2  

左秀玲  苏奋振  张宇  吴文周  吴迪 《地理学报》2020,75(3):647-661

全球变化下,珊瑚礁保护区是保护生物多样性、增强珊瑚礁对气候变暖抵抗力的有效方式,而维持珊瑚礁弹性是其核心内容。针对珊瑚礁最具有威胁性的热压力因子,基于南海1982—2009年卫星观测海表面温度（SST）数据和CMIP5加拿大地球系统模式CanESM2模型预估的2006—2100年南海SST数据构建热压力强度模型,从维持珊瑚礁弹性的角度识别IPCC RCP 4.5和RCP 8.5情景下南海诸岛保护优先区。结果表明：RCP 4.5和RCP 8.5情景下13%左右的南海诸岛珊瑚礁识别为保护优先区。根据热压力强度与珊瑚抵抗力及避难所关系,西沙群岛七连屿和晋卿岛近年观测与未来预估的热压力强度均比较低,在保障其服务功能的基础上建议实施完全保护;东沙群岛东沙环礁和中沙环礁排洪滩近年观测急性热压力强度较高但未来预估热压力强度较低,建议实施50%禁止利用保护;中沙群岛黄岩岛近年观测和未来预估的急性热压力强度均比较低,建议实施50%多用途保护。南沙群岛有14%左右的珊瑚礁识别为保护优先区,根据其热压力强度可实施30%~100%禁止利用保护或30%~50%多用途保护。RCP 4.5和RCP 8.5情景下的南海诸岛保护优先区及保护对策,可为维持珊瑚礁生态弹性及应对全球气候变化提供重要的参考价值。  相似文献   

海岸破波带内悬沙空间分布试验研究和解析表达式     

张洋  邹志利  孙大鹏  薛武山 《海洋工程》2018,36(1):28-46

关于海岸破波带内悬沙浓度水平和垂向分布的研究对于计算海岸输沙率和地形演变具有重要意义。本研究进行了规则波、波群和不规则波三种波浪情况破波带内悬沙浓度的水平和垂向分布的试验测量。试验在大尺度波浪水槽进行,接近实际海岸波况尺度。给出了破波带内多断面悬沙垂向分布的细致测量结果,并以此为基础给出了预报实际海岸破波带内悬沙浓度水平和垂向分布解析表达式,讨论了形成这些分布的物理原因和不同波况、不同破波带区域对分布的影响。  相似文献   

Lidar-aided analysis of boreal forest backscatter at Ku band     

《International Journal of Applied Earth Observation and Geoinformation》2020

This paper analyzes the backscatter of the microwave signal in a boreal forest environment based on a Ku -band airborne Frequency-Modulated Continuous Waveform (FMCW) profiling radar—Tomoradar. We selected a half-managed boreal forest in the southern part of Finland for a field test. By decomposing the waveform collected by the Tomoradar, the vertical canopy structure was achieved. Based on the amplitude of the waveform, the Backscattered Energy Ratio of Canopy-to-Total (BERCT) was calculated. Meanwhile, the canopy fraction was derived from the corresponding point cloud recorded by a Velodyne VLP-16 LiDAR mounted on the same platform. Lidar-derived canopy fraction was obtained by counting the number of the first/ the strongest returns versus the total amount of returns. Qualitative and quantitative analysis of radar-derived BERCT on lidar-derived canopy fraction and canopy height are investigated. A fitted model is derived to describe the Ku-band microwave backscatter in the boreal forest to numerically analyze the proportion contributed by four factors: lidar-derived canopy fraction, radar-derived canopy height, the radar-derived distance between trees and radar sensor and other factors, from co-polarization Tomoradar measurements. The Root Mean Squared Error (RMSE) of the proposed model was 0.0958, and the coefficient of determination R2 was 0.912. The fitted model reveals that the correlation coefficient between radar-derived BERCT and lidar-derived canopy fraction is 0.84, which illustrates that lidar surface reflection explains the majority of the profiling /waveform radar response. Thus, vertical canopy structure derived from lidar can be used for the benefit of radar analysis.  相似文献   

300 BC-1900 AD无定河流域城镇时空格局演变   总被引：2，自引：1，他引：1  

佟彪  党安荣  许剑 《地理学报》2019,74(8):1508-1524

通过分析和整理从战国中晚期（约300 BC）至清末（约1900 AD）无定河流域历代县级及以上城址的位置、兴废年代数据,结合行政区划沿革、经济社会发展、政权更迭等资料,分析流域城镇格局的时空演变过程。研究表明：① 受气候周期性波动影响,无定河流域城镇的兴起与衰废具有明显的周期性特征,城镇几何中心的移动轨迹具有明显的“西北—东南”向潮汐性运动特征;② 城址存续年限普遍较短,具有明显的阶段性特征,流域内曾存在过4个阶段性中心城镇,中心城镇移动的方向和过程与城镇几何中心的潮汐性移动过程趋势一致;③ 流域城镇空间格局可分为3种类型,即秦汉与隋唐时期的沿河流谷地分布,宋、明两代的沿边境线与长城分布,以及元、清两代集中于流域下游分布。流域城镇未来的发展布局应重视气候变化对城镇分布的长期影响,关注区域环境的脆弱性,合理安排城镇体系发展规模与布局。  相似文献   

Parallelization of the flow-path network model using a particle-set strategy     

Fangli Zhang 《International journal of geographical information science》2019,33(10):1984-2010

High-performance simulation of flow dynamics remains a major challenge in the use of physical-based, fully distributed hydrologic models. Parallel computing has been widely used to overcome efficiency limitation by partitioning a basin into sub-basins and executing calculations among multiple processors. However, existing partition-based parallelization strategies are still hampered by the dependency between inter-connected sub-basins. This study proposed a particle-set strategy to parallelize the flow-path network (FPN) model for achieving higher performance in the simulation of flow dynamics. The FPN model replaced the hydrological calculations on sub-basins with the movements of water packages along the upstream and downstream flow paths. Unlike previous partition-based task decomposition approaches, the proposed particle-set strategy decomposes the computational workload by randomly allocating runoff particles to concurrent computing processors. Simulation experiments of the flow routing process were undertaken to validate the developed particle-set FPN model. The outcomes of hourly outlet discharges were compared with field gauged records, and up to 128 computing processors were tested to explore its speedup capability in parallel computing. The experimental results showed that the proposed framework can achieve similar prediction accuracy and parallel efficiency to that of the Triangulated Irregular Network (TIN)-based Real-Time Integrated Basin Simulator (tRIBS).  相似文献   

基于高斯烟羽模型的船舶尾气扩散研究     

付金宇  李颖 《海洋通报》2018,(2):235-240

为有效对港区大气污染进行治理、分析船舶尾气,本文详细介绍了一种基于高斯烟羽模型,通过MATLAB模拟仿真模型,其包括实验仿真过程、技术原理及理论模型对船舶尾气扩散进行的研究。该模型是在传统的高斯烟羽模型的基础上,通过对实源像源进行加权选择输入参数;通过矢量合成确定了气体扩散的方向,利用合成后的"风速"进行计算仿真,有效模拟了船舶尾气在港区或者海洋环境中的气体扩散模型。其模型简单且可以有效模拟船舶尾气扩散。并且进一步对后续模型的精确优化进行分析。  相似文献   

浙南近海虾类群落结构及其多样性分析   总被引：1，自引：0，他引：1  

陈伟峰  彭欣  叶深  谢起浪  陈少波  汪振华  陈骁 《海洋科学》2018,42(3):37-45

作者根据2015年11月(秋季)、2016年2月(冬季)、2016年5月(春季)和2016年8月(夏季)对浙南近海进行的渔业资源调查数据,用生物量作为虾类资源分布的数量指标,对该海域虾类的组成、数量分布以及季节变化进行分析。结果显示:该区域共鉴定出虾类30种,隶属于10科21属,以对虾科(Penaeidae)虾类最多,其次为管鞭虾科(Solenoceridae),长臂虾科(Palaemonida)位居第3位。按季节来看,秋季共鉴定虾类27种,各站位平均生物量为6.97 kg/km2,优势种为凹陷管鞭虾(Solenocera koelbeli)、中国毛虾(Acetes chinensis)和中华管鞭虾(Solenocera crassicornis)等3种;冬季鉴定出虾类25种,平均生物量为1.65 kg/km2,优势种为凹陷管鞭虾、扁足异对虾(Atypopenaeus stenodactylus)、日本鼓虾(Alpheus japonicus)、鲜明鼓虾(Alpheus digitalis)、中国毛虾、中华管鞭虾和周氏新对虾(Metapenaeus joyneri)等7种;春季20种,平均生物量为2.22 kg/km2,优势种为戴氏赤虾(Metapenaeopsis dalei)、东海红虾(Metapenaeopsis dalei)和中华管鞭虾等3种;夏季16种,平均生物量为10.36 kg/km2,优势种有鹰爪虾(Trachysalambria curvirostris)和中华管鞭虾等2种。Margalef丰富度指数(D)、Shannon-Wiener多样性指数(H′)和Pielou均匀度指数(J′)秋季均低于冬季。秋冬季受到浙闽沿岸流影响,温度、盐度相对较低,夏季受到台湾暖流外侧影响,温度、盐度相对较高,且各季节间由于瓯江、椒江、飞云江、鳌江等陆源性冲淡水的影响,盐度、温度变化相对较大,使得该区域的物种不得不适应一个跨度较大的温盐范围,广温广盐性种类为主。  相似文献   

基于SODA资料的南海表层风能输入的空间分布与长期趋势研究     

杨倩  崔超然  张宇  刘志宇  管玉平  黄瑞新 《热带海洋学报》2018,37(6):41-48

海面风不仅是驱动上层海洋运动的主要动力, 其能量也是维持海洋表层流动的主要机械能来源。为了分析南海表层流风能输入的变化, 用SODA(Simple Ocean Data Assimilation)(1901—2010)资料估算了风向南海表层流(表层地转流+表层非地转流)的能量输入。结果表明, 风向南海表层流、表层地转流和表层非地转流输入的能量总体均呈减少趋势, 110年间分别减小了约56%、65%和49%。导致风能输入减小的最主要因素是风应力的减弱(减小了35%)。由于南海受季风系统的控制, 风向表层流及其各成分输入的能量呈现出显著的季节性变化。冬季风能输入最强, 高值区位于南海西部及北部区域, 呈一个显著的“回力镖”状结构。这些结果对深入认识南海环流具有理论意义。  相似文献