Predicting quantiles of water quality from catchment characteristics

Water quality is often highly variable both in space and time, which poses challenges for modelling the more extreme concentrations. This study developed an alternative approach to predicting water quality quantiles at individual locations. We focused on river water quality data that were collected over 25 years, at 102 catchments across the State of Victoria, Australia. We analysed and modelled spatial patterns of the 10th, 25th, 50th, 75th and 90th percentiles of the concentrations of sediments, nutrients and salt, with six common constituents: total suspended solids (TSS), total phosphorus (TP), filterable reactive phosphorus (FRP), total Kjeldahl nitrogen (TKN), nitrate-nitrite (NO_x), and electrical conductivity (EC). To predict the spatial variation of each quantile for each constituent, we developed statistical regression models and exhaustively searched through 50 catchment characteristics to identify the best set of predictors for that quantile. The models predict the spatial variation in individual quantiles of TSS, TKN and EC well (66%–96% spatial variation explained), while those for TP, FRP and NO_x have lower performance (37%–73% spatial variation explained). The most common factors that influence the spatial variations of the different constituents and quantiles are: annual temperature, percentage of cropping land area in catchment and channel slope. The statistical models developed can be used to predict how low- and high-concentration quantiles change with landscape characteristics, and thus provide a useful tool for catchment managers to inform planning and policy making with changing climate and land use conditions.     

含有集约束向量极值问题的最优性条件

在序线性拓扑空间里研究了含有集约束向量极值问题的最优性条件,并建立了充分性和必要性条件.     

Poisson-Logistic二元复合极值模型在平台甲板标高设计中的应用

考虑到平台所在海区台风出现的频次及其诱发之风、浪、潮、流极端海况联合出现的概率特性，本文推导出Poisson—Logistic二元复合极值模式，并以平台甲板标高进行实例计算。新模式增加了概率模型的物理内涵，解决了Logistic模型阈值选取的任意性。对海洋工程极端海况荷载组合预测具有广泛的应用前景。     

Long-Period Distribution of Wave Heights and Its Application

This paper reveals that the long-period statistic distribution of the characteristic heights of deep-water waves assumes the lognormal distribution. Thereafter, the largest wave-height which may occur in the service life of coastal structures is derived in this paper.     

渤海南部海域年极值波浪和设计波浪的特征研究

本文用统计计算和后报方法，获得了本海域不同海区多年年极值波高（Ｈ１／１０）资料。用Ｐ－Ⅲ型和短期测波资料频率分析方法，估算了各海区的设计波高，并依据文献［３］计算出对应的平均周期。用Ｋｏｌｍｏｇｏｒｏｆｆ适合度方法检验所得的结果表明，依Ｐ－Ⅲ型方法拟配的理论频率曲线与经验点十分吻合，从而确定了本海域不同海区最佳的设计波浪。分析本海域年极值波浪的基本特征表明，本海域除了渤海湾北部海区以外，主浪向一般为ＮＮＥ向，渤海海峡区的年极值波高和设计波高均为最大，而向莱州湾及渤海湾沿岸海区逐渐减小；在沿岸海区，由龙口至黄河口一带的极值波高较大。     

新世纪大洋钻探"三角鼎立"中的欧洲联合体

欧洲为了与美国、日本在IODP中处于同等重要的地位，成立了由ODP成员参加的欧洲大洋钻探科学指导委员会（ESCOD）和JEODI组织，并开展了IODP之前的一系列准备活动。在其中的APLACON会议上，论证了IODP中第三类特定钻探平台的必要性，讨论了该类平台在某些研究范围内的重要作用，包括研究地球历史中的极端气候（北极海区）、重建白垩纪－第三纪的水文地理学、气候的快速变化、沉积盆地形成与过程以及固体地球过程等。     

Red Tide Frequency Analysis Using the Extreme Value Theory

In recent years, the red tide erupted frequently, and caused a great economic loss. At present, most literatures emphasize the academic research on the growth mechanism of red tide alga. In order to find out the characters of red tide in detail and improve the precision of forecast, this paper gives some new approaches to dealing with the red tide. By the extreme values, we deal with the red tide frequency analysis and get the estimation of T-times red tide level U （T） , which is the level once the consistence of red tide alga exceeds on the average in a period of T times.     

一个基于TOPEX卫星极端海面风速预测的海洋地理信息系统

在基于 TOPEX卫星数据建立全球极端海面风速预测模型的基础上 ,开发出用于极端海面风速预测和可视化预测结果的海洋地理信息系统 (MGIS)。并论述全球极端海面风速预测的意义和 MGIS在预测过程中的重要性及必要性 ;给出全球极端海面风速预测的统计模型 ;简述极端海面风速预测海洋地理信息系统的结构、工作流程和功能 ;同时 ,对系统的预测结果进行初步分析     

南海东北部台风潮的数值后报及极值增水估计

本研究对近40年来影响南海东北部陆架海区的28次台风引起的风暴潮进行了数值后报,其中8个过程的沿岸后报增水值与实测值进行了比较,表明后报值与实测值符合良好,90%以上的最大增水值偏差在30厘米以下。为了得出本海区多年一遇的台风增水极值,在后报台风路径密集处选择了9个不同水深点,对每点取出各次台风下的最大增水值,然后用Weibull分布进行拟合,得出了各点的极值分布。     

Extreme value analysis of diamond-size distributions

Extreme value analysis provides a semiparametric method for analyzing the extreme long tails of skew distributions which may be observed when handling mining data. The estimation of important tail characteristics, such as the extreme value index, allows for a discrimination between competing distribution models. It measures the thickness of such long tailed distributions, if only a limited sample is available. This paper stresses the practical implementation of extreme value theory, which is used to discriminate a lognormal from a mixed lognormal distribution in a case study of size distributions for alluvial diamonds.