基于L0梯度平滑与图像分块聚类的海天线检测

海天线检测在海洋工程安防活动中具有重要的意义，真实海洋环境中的海天线检测易受云朵、海浪、光照变化、目标遮挡物、边界模糊等外界干扰。为了实现对真实海洋环境中海天线的检测，本研究提出一种基于L0梯度平滑和图像分块聚类的海天线检测算法。首先，对图像进行L0梯度平滑滤波，以增强海天线边缘，弱化非海天线因素干扰；接着，将图像沿着竖直方向分割成若干等宽图像块，以降低整体环境干扰，加强局部海天线检测效果；然后，通过Canny算子和霍夫变换提取每个分割图像块中的直线段；最后，采取K means聚类算法提取每个图像块中的海天线段，拟合生成完整海天线。实验结果表明，在真实的海天线数据集中，本研究方法获取的矩形框重叠率平均精度为93.22%，角度差平均精度为7.66%，均高于文中选取的近年典型对比算法。满足实际海天线检测抗干扰强、准确率高、适应性广等要求。     

Effect of Temporal Resolution of NDVI on Potential Evapotranspiration Estimation and Hydrological Model Performance

Normalized difference vegetation index (NDVI) data, obtained from remote sensing information, are essential in the Shuttleworth-Wallace (S-W) model for estimation of evapotranspiration. In order to study the effect of temporal resolution of NDVI on potential evapotranspiration (PET) estimation and hydrological model performance, monthly and 10-day NDVI data set were used to estimate potential evapotranspiration from January 1985 to December 1987 in Huangnizhuang catchment, Anhui Province, China. The differences of the two calculation results were analyzed and used to drive the block-wise use of the TOPMODEL with the Muskingum-Cunge routing (BTOPMC) model to test the effect on model performance. The results show that both annual and monthly PETs estimated by 10-day NDVI are lower than those estimated by monthly NDVI. Annual PET from the vegetation root zone (PETr) lowers 9.77%-13.64% and monthly PETr lowers 3.28%-17.44% in the whole basin. PET from the vegetation interception (PETi) shows the same trend as PETr. In addition, temporal resolution of NDVI has more effect on PETr in summer and on PETi in winter. The correlation between PETr as estimated by 10-day NDVI and pan measurement (R2= 0.835) is better than that between monthly NDVI and pan measurement (R2 = 0.775). The two potential evapotranspiration estimates were used to drive the BTOPMC model and calibrate parameters, and model performance was found to be similar. In summary, the effect of temporal resolution of NDVI on potential evapotranspiration estimation is significant, but trivial on hydrological model performance.     

The standards for skill assessment of operational marine forecast system

To support navigational and environmental applications in coastal waters, marine opera- tional forecast models must be developed and implemented. A forecast model must guarantee that it is scientifically sound and practically robust for performance and must meet or excel all target frequencies or durations before being released to the public. This paper discusses the standard policies and procedures for evaluation of operational marine forecast models. The primary variables to be evaluated are water lev- els, currents and water density (water temperature and salinity).     

《水文知识读本》出版

河北省水文水资源勘测局组织30余名技术人员,历时三年,编写完成的《水文知识读本》一书,日前已由中国水利水电出版社出版发行。该书由王春泽、乔光建等编著,水利部水文局邓坚局长作序。全书共分上中下三册,约222万字。《水文知识读本》主要分水文学基础     

RELATION BETWEEN PRECIPITATIONAND SEDIMENT TRANSPORT IN THE DASHA RIVER WATERSHED

The study on sediment production and its relationship with climatic and hydrological factors in watershed is a major environment issue of concern in the international community. Based on the observational records covering the period from 1954 to 1999, the characteristics of precipitation changing over the Dasha River Watershed in Anhui Province and its relation to sediment yield were studied using tendency analysis and correlation analysis.Results showed that the precipitation of the Dasha River Watershed has high variability. In those 46 years, 34% of spring rainfall, 58% of summer rainfall and 30% of annual rainfall will be considered anomaly. The gray correlation analysis shows that sediment discharge correlates most closely with the frequency of the rainstorm with a daily precipitation above 100mm, secondly with the frequency of the rainstorm with a daily precipitation of 50-100mm, and thirdly with the number of rainy days. Their correlation coefficients are 0.98,0.90 and 0.85 respectively. In addition,the paper suggests the major countermeasures and methods for controlling of soil and water losses in this area.     

土壤质地对中国区域陆面过程模拟的影响

利用陆面过程模式(CLM3.5)和中国区域两种土壤质地数据(分别来自第二次中国土壤调查SNSS和联合国粮食农业组织FAO),研究了土壤质地变化对于模式模拟的陆表水热变量的影响。结果显示,土壤质地对土壤水文学变量的影响远大于对土壤热力学变量的影响,尤其是对于饱和土壤含水量和饱和水力传导率的影响。对于模式的输出,土壤质地影响比较明显的有土壤湿度、总径流和土壤渗透等水文学变量以及地表潜热、地表感热和土壤热通量等热力学变量,而影响相对较小的有地面吸收的太阳辐射和地表反照率。同时,发现基于SNSS模拟的土壤湿度与站点观测值更加接近。因此,本研究认为基于SNSS土壤质地数据可以有效地改进模式模拟结果,建议以后在陆面模式试验中尽可能使用以观测为基础的SNSS土壤质地数据。     

流域生态水文过程模拟研究进展

生态水文学作为生态学和水文学的交叉学科,得到了相关研究者的广泛关注,并成为水文水资源研究领域中的一个热点,生态水文过程主要包括水文过程、生态过程以及二者之间相互作用的过程。从生态水文学内涵的角度,对山地、湿地、干旱区生态水文过程模拟以及流域集成模拟进展做了阐述,并分析建模的策略和统计了部分生态水文模型,考虑了建模过程中的尺度、数据、精度3个关键问题。并对生态水文模拟发展趋势做了展望,指出在未来的研究中应更多的关注以下几个方面:①生态水文过程模拟建模基础研究;②生态水文过程集成模拟研究;③基于数据库和GIS/RS技术的生态水文过程耦合模拟研究;④与原型观测相结合的生态水文过程模拟研究。建立符合我国实情的生态水文模型,是现阶段我国生态水文学研究的重要任务。     

水文山流域土壤水δ~(18)O空间分布异质性研究

流域非饱和带和土壤层的空间异质性是构成水文过程非线性的主要根源,也是水文实验研究中的薄弱环节,特别是其空间分布,传统研究集中于等值线类型的定性描述。研究通过实验流域土壤水δ~(18)O这一非饱和带的主要空间变量,结合传统统计和地统计方法分析不同深度土层δ~(18)O的变化机制和分布空间的分布变异情况,为地统计学方法对水文参数空间变异定量的应用提供数据基础。研究结果显示:15 cm土层土壤水δ~(18)O半方差函数空间模型从纯金模型到高斯和指数模型,再回到纯块金模型,变化剧烈。通过蒸发分馏估算其蒸发强度,得到45cm土层最强(11%),且有关离散性质的极差、标准差和偏度差绝对值也都以45cm土层为最大。说明了在这非饱和带过程中,起关键作用的不是所想象的表面土层,而是中部土层,在水文山实验流域则是地面下的45cm土层;45cm土层的δ~(18)O符合高斯模型和指数模型,且高斯模型中块金与基台值之比C_0/(C_0+C_1)接近于零,说明在下渗、蒸发、迁移以及和土壤中原有δ~(18)O融合后,形成更强的空间自相关性。80cm深度参与"混合"机制的是46d前降雨的"老水",其δ~(18)O的空间自相关性变化则呈现明显滞后性,48 h后才呈现出空间的相关性。可见,经典统计学点参数变量和地统计学区域化变量方法在流域水文参数空间定量方面的有效性,同时在流域水文机制方面出现有意外的、特别是与传统概念相悖的现象。     

关于比较水文学的研究

比较水文学是水文研究中的新课题。作者根据国际水文计划(IHP)组织的研究活动介绍了这一课题最新动向;探讨了比较水文的概念,目的与研究方法;提出在我国开展这一研究的有利条件。认为及早起步开展工作,可望走在世界前列;最后建议从水文类型系统、水文过程、水文实验方面打好基础,建立比较水文信息系统,发展水文成因模型,制定应用方案。