福州市地表温度热点及时空变化分析

中国作为世界第一大发展中国家,近年来城镇化发展迅速,大量自然地表转化为人工地表,从而引起了一系列环境问题,其中以城市热岛问题最为显著。因此如何缓解因城市化进程的加快引起的城市热岛效应已成为热门研究方向。为精确分析城市空间格局对热集聚的影响,本研究利用2000年5月4日的Landsat ETM+和2016年7月27日获取的Landsat OLI两期遥感影像,获取福州市的土地覆盖信息并进行精度验证。在地表温度（Land Surface Temperature, LST）反演基础上通过热点分析（Getis-Ord Gi*）,并结合不透水面（Impervious Surface Area, ISA）信息来研究城市化进程中福州市16 年来 LST的变化特性,空间集聚特性及其产生的尺度效应。热点分析结果显示：① 通过分析福州市内各地和热点中心的距离与LST的关系可较好地反映空间热聚集。2000 年在距热点中心0.97、1.03、0.95 km范围内热聚集明显;2016 年则增长到分别在距热点中心半径1.89、2.01、2.10、2.05、2.13 km范围内热集聚显著且热点区数量也从3 个增加至5 个。热集聚区（热点区和较热区）总面积在此期间从15.7%增至47.3%;② 由于热点图中的热点区和冷点区的形成不单取决于LST的高低,因此热点分析与空间自相关分析方法相比,能更直观地分析土地覆盖变化对LST的影响,了解城市内部热强度变化的细节。本研究采用的热点分析方法可用于城市环境保护与规划,将来还可作为城市土地规划与热环境影响的分析依据。同时可利用热点分析图模拟城市微气候,估算城市绿地降温程度等。此外,未来还可基于此进一步探讨更多时相以及不同城市的对比分析,特别是对不同城市类型如带状城市,多中心城市及中心城市等的研究。     

一种海洋混合层深度的智能识别方法研究

文章提出了一种识别混合层深度的人工智能方法。该方法在温度(密度)与压强(或深度)间建立线性模型, 并且将其系数和方差做成一组表征廓线特征的统计量。初始时为模型设定一个主观的先验分布, 在一个自海表向下移动的窗口内通过贝叶斯链式法则和最小描述长度原理学习新数据, 得到系数均值的最大后验概率估计。用F-检验识别系数发生突变的位置, 以此确定混合层的存在性及其深度。通过2017年2月太平洋海域的地转海洋学实时观测阵(Array for Real-time Geostrophic Oceanography, ARGO)数据进行测试, 并且以质量因子(Quality Index, QI)值作为判断识别混合层深度结果准确性的依据, 发现该方法相比于梯度法、阈值法、混合法、相对变化法、最大角度法和最优线性插值法在识别结果上具备更大的QI值。表明该方法能够准确识别混合层深度。     

基于ERA-20C再分析数据的中国近海波候研究

基于ERA-20C再分析数据,综合分析了1950—2010年间中国近海的海表风速、风浪、涌浪和混合浪的分布特点。结果表明,中国近海的风场主要受东亚季风控制,在南海南部靠近越南的海域夏季形成7 m/s的风速大值中心,冬季风速则可达9 m/s。风浪场的空间分布特点与风场相似,而受传播效应和浅水效应的影响,涌浪场四季均在吕宋海峡和东海东南部出现波高的大值中心。春夏季节中国近海大部分海域涌浪占优,与风速大值中心对应,夏冬季节南海南部10°N附近存在风浪池。趋势分析结果显示,风速和混合浪有效波高的线性趋势呈现相似的空间分布,南海的风速和波高分别以0.27 cm·s^-1/a和0.74 cm/a的速率显着增加。而渤海分别以-0.49 cm·s^-1/a和-0.85 cm/a的速率显著降低,黄海的变化率分别为-0.43 cm·s^-1/a和-0.79 cm/a。将中国近海风速和波高的年际变化分别与气候指数尼诺3.4进行相关分析,结果显示,冬季大部分海域的相关系数为负,而夏季在南海和东海海域则为正。     

Specifying a joint space- and time-lag using a bivariate Poisson distribution

Separate space- or time-lags have been considered regularly in data analyses; as space–time models are more recently being studied extensively in data analytic fashion, joint estimation of both lags has to be considered explicitly. This paper addresses this issue, taking into special consideration parametric parsimony together with specification richness; use of the bivariate Poisson frequency distribution is advocated and applied to an empirical case. The relation of this approach to random effects specifications is investigated. Data for Belgian regional products constitute the empirical case study.

Mixed layer depth climatology of the North Pacific based on Argo observations

A monthly mean climatology of the mixed layer depth (MLD) in the North Pacific has been produced by using Argo observations. The optimum method and parameter for evaluating the MLD from the Argo data are statistically determined. The MLD and its properties from each density profile were calculated with the method and parameter. The monthly mean climatology of the MLD is computed on a 2° × 2° grid with more than 30 profiles for each grid. Two bands of deep mixed layer with more than 200 m depth are found to the north and south of the Kuroshio Extension in the winter climatology, which cannot be reproduced in some previous climatologies. Early shoaling of the winter mixed layer between 20–30°N, which has been pointed out by previous studies, is also well recognized. A notable feature suggested by our climatology is that the deepest mixed layer tends to occur about one month before the mixed layer density peaks in the middle latitudes, especially in the western region, while they tend to coincide with each other in higher latitudes.     

Wave breaking on turbulent energy budget in the ocean surface mixed layer

As an important physical process at the air-sea interface, wave movement and breaking have a significant effect on the ocean surface mixed layer （OSML）. When breaking waves occur at the ocean surface, turbulent kinetic energy （TKE） is input downwards, and a sublayer is formed near the surface and turbulence vertical mixing is intensively enhanced. A one-dimensional ocean model including the Mellor-Yamada level 2.5 turbulence closure equations was employed in our research on variations in turbulent energy budget within OSML. The influence of wave breaking could be introduced into the model by modifying an existing surface boundary condition of the TKE equation and specifying its input. The vertical diffusion and dissipation of TKE were effectively enhanced in the sublayer when wave breaking was considered. Turbulent energy dissipated in the sublayer was about 92.0% of the total depth-integrated dissipated TKE, which is twice higher than that of non-wave breaking. The shear production of TKE decreased by 3.5% because the mean flow fields tended to be uniform due to wave-enhanced turbulent mixing. As a result, a new local equilibrium between diffusion and dissipation of TKE was reached in the wave-enhanced layer. Below the sublayer, the local equilibrium between shear production and dissipation of TKE agreed with the conclusion drawn from the classical law-of-the-wall （Craig and Banner, 1994）.     

南沙群岛海域混合层深度季节变化特征

基于南沙群岛海域综合科学考察11个航次的实测资料,研究了南沙群岛海域的混合层深度季节变化特征。研究结果表明,南沙群岛海域混合层深度存在明显的季节变化,并且与季风和海表热通量的变化密切相关。春季,风速较小且风向不稳定,海面得到的净热通量全年最大,上层水体层结稳定,混合层深度较小;夏季,南海西南季风盛行,上层为反气旋式环流,海面得到的净热通量减少,混合层呈加深的趋势;秋季,海面净热通量继续减少,混合层深度达到最大值;冬季,东北季风驱动下形成的上层气旋式环流引起深层冷水的上升,限制了混合层的加深。     

粉喷桩的应用研究综述

粉喷桩具有低污染、低噪音、有效实用、施工简便快捷、施工工期短、技术效果好和费用底等特点而受到普遍关注,但其也存在一定的不足。本文分析了粉喷桩在工程中应用的研究现状,介绍了粉喷桩与其他工程措施相结合的实例,并对以后的研究方向提出了看法。     

不同辐射背景下大西洋热盐环流下沉区混合层深度变化

基于政府间气候变化专门委员会(Intergovernmental Panel on Climate Change,IPCC)4种最新辐射强迫情景,利用ECHAM5/MPI-OM(European Centre Hamburg Model 5/Max Planck Institute Ocean Model)气候模式输出的1850—2300年逐月混合层深度、海表面温度、海表面盐度数据,分析大西洋热盐环流下沉区混合层深度的变化情况。结果表明:随辐射强迫增加,热盐环流下沉区混合层深度下降,混合层深度振荡周期在格陵兰-冰岛-挪威海(Greenland Sea–Iceland Sea–Norwegian Sea,GIN)海域减小,在拉布拉多海(Labrador Sea,LAB)海域变化不大;与GIN海域相比,LAB海域混合层深度对辐射强迫变化更敏感;两海区温度对混合层深度的影响时间较长,混合层深度对盐度的变化反应迅速;混合层深度变化的主导因素在LAB海域中为盐度,而在GIN海域,低辐射强迫下温度主导混合层深度变化,中高辐射强迫下温度与盐度共同起主导作用。     

鲤鱼配合饲料中添加无机盐效果的研究

为查明在鲤鱼配合饲料中添加无机盐的实际效果，在水库网箱中进行了饲料中添加不同无机盐对鲤生长影响的试验研究。结果表明：饲料中添加磷有稳定的积极作用，为必须添加的营养元素；而实验中添加的锌、镁和铜等成分则有负作用，故额外添加和水中含量较高会对鲤鱼生长产生抑制作用。另外，还发现多种元素混合使用时，有相互拮抗作用，减少了磷的正作用及锌、铜的负作用。据此认为，在鲤鱼配合饲料中添加混合无机盐定型产品不一定能达到预期效果，其配方应与配合饲料中大量成分的配方相结合