Evaluation of sensitivity of land surface hydrology representations with and without land–atmosphere feedback

This paper compares various ways of quantifying the importance of land–atmosphere feedback. A widely used land surface hydrology model is used in coupled (to a planetary boundary layer model) and uncoupled modes to compare the adequacy of different feedback indices. It is found that existing feedback indices are primarily based on ‘one factor at a time’ sensitivity analysis and cannot adequately capture the interaction between land and atmosphere. A new index is used which combines factorial design concepts and traditional sensitivity analysis. This index is shown to capture and quantify the strength of interaction between land surface parameters and atmosphere. To assess the effects of forcing characteristics on the stand alone model sensitivity, several ways to specify near-surface atmospheric conditions are evaluated. It is found that commonly used forcing conditions (e.g. model generated or observed time-series of near-surface atmospheric variables) may not be adequate to mimic the coupled model environment for evaluating the land surface representations. The partially coupled model sensitivity is shown to capture a major feedback loop related to water holding capacity, surface fluxes and near-surface atmospheric processes. These results suggest that sensitivity from the stand alone model should be interpreted with caution and future evaluations should strive to incorporate land–atmosphere feedback, at least within a partially coupled model. © 1997 John Wiley & Sons, Ltd.     

卫星遥感海南岛气候特性的研究

利用NOAA极轨气象卫星的AVHRR资料，研究了海南岛干、湿两季在无云情况下的下垫面短波反射率、植被指数、下垫面温度和射出长波辐射的分布及变化特征。结果表明利用气象卫星资料可以较详细地了解气候形成的主要因素之一——下垫面状况。     

地震信息网络数据的动态存储方法研究

为了提高地震信息网络数据存储的效率和稳定性,本文提出一种地震信息网络数据的动态储存方法。首先,设计和分析地震信息网络数据的动态存储系统中的硬件部分,基于Hadoop的分布式集群大数据动态存储系统,整合多台存储服务器,为一个集群系统,并平衡存储服务器负载情况,获取性能指标的比例值,通过加权公式获取综合性能参数,根据综合负载指标和服务器综合指标参数获取最佳存储服务器。对本文系统、高速数据存储系统和网络编码云存储系统进行大数据动态存储对比实验。实验结果表明:地震信息网络数据的动态存储耗时最短,存储效率最快;具有较高存储稳定性,且不会出现过载问题。     

结构性参数在黄土地基沉降计算中的应用研究

弦线模量法建立了考虑黄土基本物性指标及附加应力综合影响的弦线模量函数,应用分层总和法计算黄土地基的变形量,并在陕西关中黄土地区工程实践中获得良好的预测结果,而在分析兰州等其他黄土地区地基沉降时,结果出现偏差,究其原因,与计算中忽视了天然状态下黄土的结构性特征有关。以弦线模量法为基础,通过西安近郊4处土样试验和大量载荷试验资料,分析黄土的构度指标与压缩模量、孔隙比、含水量的关系,并将构度指标引入弦线模量表,深化结构性参数在地基沉降变形计算中的理论。     

新疆艾比湖流域枯、丰水期三维荧光光谱特性及其与水质的关系

以艾比湖流域主要入湖河流为研究对象,在5月（丰水期）和8月（枯水期）分别沿博尔塔拉河（博河）和精河进行采样,采用平行因子模型（PARAFAC）和三维荧光区域积分法对水体三维荧光特性进行研究并对其与水质的关系在枯、丰水期下的变化进行探讨.结果表明①河流DOM在枯水期与丰水期都含有C1（240、425 nm） UVC类腐殖质,C2（225、290 nm）紫外区内络氨酸类有机物,C3（230/280、330 nm）蛋白类有机物,C4（265、260 nm）腐殖质类共4种组分.通过对水体三维荧光进行区域积分可以看出DOM荧光成分的占比在不同时期的变化.博河在枯水期时EEM光谱中的区域Ⅲ富里酸含量低于丰水期,枯水期时区域Ⅱ芳香类蛋白质、区域Ⅳ可溶性微生物代谢物以及区域Ⅴ类腐殖质酸高于丰水期;对于精河来说,区域Ⅱ芳香类蛋白质和区域Ⅳ可溶性微生物代谢物在枯水期的含量高于丰水期,区域Ⅲ富里酸和区域Ⅴ类腐殖质酸的含量枯水期低于丰水期,这表明水体腐质化程度较高.②本研究选取了一些常规的荧光指数来描述枯、丰水期水体的荧光指数特性.经研究发现,精河的荧光指数、自生源指数和腐殖化指数在不同时期的变化幅度较小,而博河的变化幅度较大.③将荧光指数与水质参数进行相关性分析并建模,结果表明枯水期自生源指数（BIX）与化学需氧量呈显著正相关,相关系数R=0.688;丰水期时BIX与铵态氮浓度呈显著负相关,相关系数R=-0.493.通过对比分析艾比湖主要入湖河流的三维荧光光谱特性与水质在枯、丰水期时的关系进一步表明水体中DOM的特性以及在枯、丰水期下的差异,为艾比湖流域的治理改善提供一定的理论支持和参考依据.     

2008年汶川MS8.0地震电离层图像信息长时程演化初探

应用改进的图像信息方法, 结合DEMETER电磁卫星的电子温度数据, 对2008年汶川M_S8.0地震进行了长时程的回溯性预测研究。 与以往的地震电离层演化图像提取异常的研究相比, 将其回溯的时程延长至震前近11个月, 并向震后延长48 d。 在长期连续的异常扰动演化图中, 出现了两个明显的异常时段, 且在震前2个月短期内异常扰动明显减弱并趋于背景值。 两个时段出现的异常扰动分布位置及其形态以及持续时间皆不重复, 这体现了前兆异常的不易确定, 难以定性及定量识别的特点。 电离层异常扰动特征的长时程研究, 有评估其预测参数和模型可靠性的实际作用, 也为应用中国卫星观测数据服务于地震预报等研究积累经验, 具有借鉴意义。     

A method to estimate the longshore sediment transport at ebb-tidal deltas based on their volumetric growth: Application to the Guadiana (Spain–Portugal border)

Current techniques assessing longshore sediment transport rates have large uncertainties, pleading for the development of alternative and complementary approaches. The present study proposes a method to estimate the decadal average rate of longshore transport at modern ebb-tidal deltas based on a sediment budget analysis of the outer shoal growth. This transport is obtained as the balance of the other contributions to the shoal with the total sediment input rate obtained from an inverse application of the inlet reservoir model. The method is applied to the Guadiana ebb-tidal delta, yielding an average longshore sediment transport rate (~85 000 m3 year⁻¹) in good agreement with expectations for the region. It is exemplified that this decadal averaged rate can be used to improve longshore sediment transport expressions in order to study its variability over shorter time scales. At the Guadiana, the yearly longshore sediment transport from the improved formula ranges from ~25 000 m³ (westward) to ~245 000 m³ (eastward) and is related to the North Atlantic Oscillation index. Overall, the proposed method constitutes an alternative tool to constrain the average longshore sediment transport rate over decades in the vicinity of tidal inlets. It is applicable to ebb-tidal deltas where the outer shoal growth (from an early to a mature stage) is well documented by bathymetric maps, and where the main transport pathways towards the outer shoal can be specified. © 2019 John Wiley & Sons, Ltd. © 2019 John Wiley & Sons, Ltd.     

大跨度钢管混凝土拱桥抗震性能指标研究

高轴压比钢管混凝土墩柱的试验结果对钢管混凝土拱肋具有较大的借鉴意义。为明确大跨度钢管混凝土拱桥的抗震性能指标,研究了高轴比钢管混凝土构件的破坏过程及延性性能。以弯矩作为性能指标将高轴压比钢管混凝土构件的试验破坏过程分为轻微损伤、有限损伤与严重损伤3个阶段,结合钢管混凝土截面性能状态的数值分析,探讨了高轴压比钢管混凝土构件的破坏机理。结果表明:高轴压比钢管混凝土构件具有一定的可用延性;提出了以计算等效屈服弯矩作为抗震性能指标,适当利用延性和实现钢管混凝土拱桥的有限损伤抗震设计,并给出了与有限损伤相关的截面性能状态及参数。研究成果弥补了规范在此方面的不足,可供高烈度地震区大跨度钢管混凝土拱桥抗震设计时参考。     

基于手机位置数据的地震灾情指标选择

选取四川阿坝州九寨沟县MS7.0地震、新疆博尔塔拉州精河县MS6.6地震、四川广元市青川县MS5.4地震作为案例分析,绘制活跃Wi Fi数量、无线网络联网设备数量、汇总在线设备数量、活跃基站数量等4种地震灾情指标在地震发生前后数量变化的折线图。根据与地震前1天变化情况的对比分析,验证地震灾情指标的可用性,选取出效果好的指标,这对进一步研究震后快速获取极震区位置、影响场方向等具有重要意义。     

Seismic responses of postyield hardening single–degree-of-freedom systems incorporating high-strength elastic material

It is widely accepted that ductility design improves the seismic capacity of structures worldwide. Nevertheless, inelastic deformation allows serious damage to occur in structures. Previous studies have shown that a certain level of postyield stiffness may reduce both the peak displacement and residual deformation of a structure. In recent years, several high-strength elastic materials, such as fiber-reinforced polymer (FRP) and high-strength steel bars, have been developed. Application of these materials can easily provide a structure with a much higher and more stable postyield stiffness. Many materials, members, and structures that incorporate both high-strength elastic materials and conventional materials show significant postyield hardening (PYH) behaviors. The significant postyield stiffness of PYH structures can help effectively reduce both peak and residual deformations, providing a choice when designing resilient structures. However, the findings of previous studies of structures with elastic-perfectly plastic (EPP) behavior or small postyield stiffness may not be accurate for PYH structures. The postyield stiffness of a structure must be considered an important primary structural parameter, in addition to initial stiffness, yielding strength, and ductility. In this paper, extensive time history and statistical analyses are carried out for PYH single–degree-of-freedom (SDOF) systems. The mean values and coefficients of variation of the peak displacement and residual deformation are obtained and discussed. A new R-μ_p-T-α relationship and damage index for PYH structures are proposed. A theoretical model for the calculation of residual deformation is also established. These models provide a basis for developing the appropriate seismic design and performance evaluation procedures for PYH structures.