Long-term trends and regime shifts in sea surface temperature on the continental shelf of the northeast United States

We investigated sea surface temperature (SST) variability over large spatial and temporal scales for the continental shelf region located off the northeast coast of the United States between Cape Hatteras, North Carolina, and the Gulf of Maine using the extended reconstruction sea surface temperature (ERSST) dataset. The ERSST dataset consists of 2°×2° (latitude and longitude) monthly mean values computed from in situ data derived from the International Comprehensive Ocean Atmosphere Data Set (ICOADS). Nineteen 2°×2° bins were chosen that cover the shelf region of interest between the years of 1854 and 2005. Mean annual and range of SST were examined using dynamic factor analysis to estimate trends in both parameters, while chronological clustering was used to determine temporal SST patterns and breakpoints in the time series that are believed to signal regime shifts in SST. Both SST and SST trend analysis show that interannual variability of SST fluctuations shows strong coherence between bins, with declining SST at the beginning of the last century, followed by increasing SST through 1950, and then rapidly decreasing between 1950 and mid-1960s, with somewhat warmer SST thereafter to present. Annual SST range decreases in a seaward direction for all bins, with strong coherence for interannual variability of range fluctuations between bins. The trend in SST range shows a decreasing range at the beginning of the last century followed by an increase in range from 1920 to the late-1980s, remaining high through present with some spatial variability. A more detailed spatial analysis was conducted by grouping the data into 7 regions using principal component analysis. We analyzed regional trends in mean annual SST, seasonal SST range (summer SST−winter SST), and normalized SST minima and maxima. Both the summer and winter seasons were also analyzed using the length of each season and amplitude of the warming and cooling season, respectively, along with the spring warming and fall cooling rates. Trends in all of the parameters were examined after low-pass filtering using a 10-point convolution filter (n=10 years) and regime shifts were identified using the sequential t-test analysis of regime shifts (STARS) method. The analysis shows some difference between regions in the timing of minimum SST with minima being reached 1 month earlier in the south (February) relative to more northern regions (March). Regional annual SST range decreased in a seaward direction. Amplitude of summer warming and the length of summer have shown fluctuations with recent years showing stronger warming and longer summers but generally not exceeding past levels. Overall, the difference in SST range, with recent larger values may be the most significant finding of this work. SST range changes have the potential to disrupt species important to local fisheries due to combinations of differing temperature tolerances, changes in reproduction potential, and changes in the distributional range of species.     

群组目标空间方向关系建模

已有的空间方向关系描述模型大都针对空间单个目标,对于群组目标空间方向关系计算模型却鲜有研究和论著。为此,提出适用于群组目标空间方向关系的定性描述与定量计算模型。首先,群组目标空间方向关系定性描述模型利用带约束的Delaunay三角剖分与动态阈值“剥皮”法求得了源目标群分布边界多边形;然后,以方向关系矩阵模型为依据对其方向关系进行了定性描述与建模;其次,运用数学形态变换理论对参考目标群进行“膨胀”,求解“膨胀”后的参考目标群与源目标群的交集;最后,在此基础上结合地学信息图谱相关理论实现了群组目标空间方向关系的定量计算与建模。实验表明,群组目标空间方向关系定性描述模型较好地顾及了群组目标的空间形态对空间方向关系的影响,能够对空间方向关系做出较为准确的定性判断;群组目标空间方向关系定量计算模型实现了群组目标空间方向关系的精确定量描述,且能够以形象直观的方式对群组目标空间方向关系进行可视化表达。2种模型较好地解决了群组目标空间方向关系的描述与计算问题。     

稀疏地理实体关系的关键词提取方法

网络文本蕴含地理实体关系抽取技术,需要高时效、强鲁棒的关键词提取方法。与监督学习方法相比,无监督学习方法能捕获文本的动态变化特征并发现新增的关系类型,因此备受关注。其中,基于频率的关键词提取方法获得广泛研究,然而,网络文本蕴含的地理实体关系分布稀疏,基于频率的方法难以直接应用于地理实体关系的关键词提取。为解决该问题,本文基于公开访问的网络资源,提出一种语境增强的关键词提取方法。首先,基于在线百科和开放的同义词词典,通过语境合并和语义融合创建增强的语境,以降低语境中词语的稀疏性。接着,Domain Frequency和Entropy频率统计方法从增强语境中自动构建一个大规模语料。然后,基于该语料选择词法特征并统计其权值,用于扩大语境中词语间的差异。最后,使用选择的词法特征度量增强语境中词语的重要性,将权值最大的词语作为描述地理实体关系的关键词,并基于大规模真实网络文本开展实验。实验结果表明：对于地理实体关系的关键词识别,本文方法的平均精度为85.5%,比Domain Frequency和Entropy方法分别提高41%和36%;对于新增关键词识别,本文方法的精度达到60.3%。语境增强的关键词提取方法能有效地处理地理实体关系分布的稀疏性,可服务于网络文本蕴含地理实体关系的抽取。     

A WEAKLY NONLINEAR WATER WAVE MODEL TAKING INTO ACCOUNT DISPERSION OF WAVE PHASE VELOCITY

This paper presents a weakly nonlinear water wave model using a mild slope equation and a new explicit formulation which takes into account dispersion of wave phase velocity, approximates Hedges‘ (1987) nonlinear dispersion relationship, and accords well with the original empirical formula. Comparison of the calculating results with those obtained from the experimental data and those obtained from linear wave theory showed that the present water wave model considering the dispersion of phase ve-locity is rational and in good agreement with experiment data.     

造父变星周光关系之实测研究进展

造父变星周光(PL)关系对于宇宙距离尺度研究和哈勃常数测定具有重要意义,所涉及的内容颇为广泛,可包括两类不同星族造父变星的PL关系,PL关系的绝对定标,周光色(PLC)关系,PL关系的金属度效应,多波段PL关系,极大光度PL关系和多相PL关系,以及非线性形式的PL关系,等等。     

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北疆地区云系的讨论

利用1998－2000年3a的GMST5静止气象卫星红外云图资料和北疆地面观测站6h降水资料，对北疆地区出现的275次云系进行分类，探讨了各类云系的生命史，出现频率，给出云型和TBB与北疆地区降水之间的关系。     

海洋内波垂向结构的一种数值算法

依据由海上实测资料得到的海水密度、声速及浮性频率随深度的分布等数据，数值求解线性内波垂向问题方程，确定了其主要模态的弥散关系及其特征函数。     

On thermodynamics of fluids,solids and superconductors

We derive the relativistic Carnot-Clausius relation and the set of fundamental equations of the thermodynamic system with the aid of Neugebauer's variational principle for several media. Some equations are already well-known in the literature but here we obtain the full set from a uniform point of view.     

一种定量化表达的空间关系模型

目前已有的空间关系模型(拓扑关系、方向关系以及度量关系)基本上是相对独立的,同时这些模型(度量关系除外)主要是定性的形式化描述,其表达精度还有待提高,因此有必要研究定量化的、组合表达的空间关系模型。提出了一种定量化表达的空间关系直方图模型,它能同时表征两个面目标之间的拓扑关系、方向关系以及度量关系,并可以定量化地分类(概率表征)空间关系类型。实验结果验证了该模型的有效性。