山地叶面积指数反演理论、方法与研究进展   总被引：2，自引：0，他引：2  

江海英  贾坤  赵祥  魏香琴  王冰  姚云军  张晓通  江波 《遥感学报》2020,24(12):1433-1449

叶面积指数LAI（Leaf Area Index）是表征叶片疏密程度和冠层结构特征的重要植被参数，在气候变化、作物生长模型以及碳、水循环研究中发挥着重要作用。遥感是获取区域及全球尺度LAI的一个重要手段，当前LAI产品主要基于遥感数据反演得到，但是多数LAI产品算法并未考虑地形特征的影响，导致山地LAI遥感反演精度不确定性大。提高山地LAI遥感反演精度亟需考虑地形因子对冠层反射率的影响，其中山地冠层反射率模型和遥感数据地形校正是提升山地LAI遥感反演精度的关键。本文围绕山地LAI遥感反演理论与方法，综合分析了国内外山地冠层反射率模型和地形校正模型的研究进展，总结了目前山地LAI遥感反演存在的问题，并讨论了未来研究的发展趋势。  相似文献   

Interaction between lateral sorting in river bends and vertical sorting in dunes     

Anne W. Baar  Steven A. H. Weisscher  Maarten G. Kleinhans 《Sedimentology》2020,67(1):606-626

Sediment is sorted in river bends under the influence of gravity that pulls the heavier grains downslope and secondary flow that drags the finer grains upslope. Furthermore, when dunes are present, sediment is also sorted vertically at the dune lee side. However, sorting functions are poorly defined, since the relation to transverse bed slope and the interaction between lateral and vertical sorting is not yet understood for lack of data under controlled conditions. The objective of this study is to describe lateral sorting as a function of transverse bed slope and to gain an understanding of the interaction between lateral and vertical sorting in river bends. To this end, experiments were conducted with a poorly sorted sediment mixture in a rotating annular flume in which secondary flow intensity can be controlled separately from the main flow velocity, and therefore transverse bed slope towards the inner bend and dune dimensions can be systematically varied. Sediment samples were taken along cross-sections at the surface of dune troughs and dune crests, and over the entire depth at the location of dune crests (bulk samples), which enabled comparison of the relative contribution of vertical sorting by dunes to lateral sorting by the transverse bed slope. The data show that lateral sorting is always the dominant sorting mechanism in bends, and bulk samples showed minor effects of vertical sorting by dunes as long as all grain-size fractions are mobile. An empirical bend sorting model was fitted that redistributes the available sediment fractions over the cross-section as a function of transverse bed slope. Comparison with field data showed that the model accurately reproduces spatially-averaged trends in sorting at the bend apex in single-thread channels. The bend sorting model therefore provides a better definition of bend sorting with conservation of mass by size fraction and adds to current understanding of bend sorting. The implication for numerical modelling is that bend sorting mechanisms can be modelled independently of dunes, allowing the application of the active layer concept.  相似文献   

基于回归模型的热带气旋条件下的海表降温参数化方案设计     

韦骏  刘欣  蒋国庆 《海洋学报(英文版)》2018,37(1):1-10

Combining a linear regression and a temperature budget formula, a multivariate regression model is proposed to parameterize and estimate sea surface temperature(SST) cooling induced by tropical cyclones(TCs). Three major dynamic and thermodynamic processes governing the TC-induced SST cooling(SSTC), vertical mixing, upwelling and heat flux, are parameterized empirically using a combination of multiple atmospheric and oceanic variables:sea surface height(SSH), wind speed, wind curl, TC translation speed and surface net heat flux. The regression model fits reasonably well with 10-year statistical observations/reanalysis data obtained from 100 selected TCs in the northwestern Pacific during 2001–2010, with an averaged fitting error of 0.07 and a mean absolute error of 0.72°C between diagnostic and observed SST cooling. The results reveal that the vertical mixing is overall the pre dominant process producing ocean SST cooling, accounting for 55% of the total cooling. The upwelling accounts for 18% of the total cooling and its maximum occurs near the TC center, associated with TC-induced Ekman pumping. The surface heat flux accounts for 26% of the total cooling, and its contribution increases towards the tropics and the continental shelf. The ocean thermal structures, represented by the SSH in the regression model,plays an important role in modulating the SST cooling pattern. The concept of the regression model can be applicable in TC weather prediction models to improve SST parameterization schemes.  相似文献   

渤海海峡跨海通道建设对城市经济联系的影响分析          下载免费PDF全文

狄乾斌  马洁 《海洋开发与管理》2018,35(3):102-108

渤海海峡跨海通道建设将极大改变环渤海乃至整个东部沿海的交通格局,势必对其目标城市大连、烟台带来直接的经济影响,同时也会对辽东半岛、山东半岛乃至东北、华北和华东不同尺度地区的经济联系产生深远影响。文章选取山东省17个和辽宁省14个地级市的地区的生产总值、城市人口以及城市间的最短时间距离等指标,测度渤海海峡跨海通道建成前后,对山东、辽宁两省区域城市经济联系的影响。研究表明:渤海海峡跨海通道建成后,对大连、烟台间的经济联系强度有显著提高,各城市经济联系度的平均增幅明显不同;同时,受距离衰减规律的影响,两省的城市分别以大连、烟台为中心,根据距离远近及城市自身发展程度分为4个层次,经济联系强度由内向外逐层次减弱;从整体上看,渤海通道的建设对带动两省城市之间的经济联系度都有大幅度提升。  相似文献   

The Upper Devonian Kellwasser event recorded in a regressive sequence from inner shelf to lagoonal pond,Catalan Coastal Ranges,Spain     

《Sedimentology》2018,65(6):2055-2087

This study, conducted in the Catalan Coastal Ranges, north‐east Spain, describes the Upper Devonian Kellwasser event in a shallowing‐upward sequence of black shales, siltstones and quartz arenites. This sequence was deposited in a progradational and regressive coastal system where the sedimentary environment evolved from the inner shelf to a lagoonal pond located landward of the shoreline. Three anomalous succeeding steps have been identified by geochemical analysis. The first one, detected on the inner shelf, was characterized by oxygen depletion and high organic productivity. The second, detected in the nearshore, was caused by hydrothermal activity occurring under normal oxic conditions. The third and most intense step was identified in the muds of the lagoonal pond and has been linked to strong anoxic conditions, elevated clastic input derived from changes in the weathering regime at the source area and moderate hydrothermal activity. The Kellwasser event is thus defined in the study area as stepwise and multi‐causal. This is the first time that the Kellwasser event has been identified in a sedimentary environment behind the shoreline. It is also the first time that it has been reported in the Catalan Coastal Ranges.  相似文献   

基于EEMD-SARIMA的对流层延迟预测模型研究     

任超  刘中流  梁月吉  甘祥前 《大地测量与地球动力学》2018,38(9):953-957

在无气象数据的条件下，提出一种基于集合经验模态分解（EEMD）和季节性自回归移动平均模型（SARIMA）的对流层延迟（ZTD）预报新方法，并分别选取长春、上海、乌鲁木齐3个地区4个季节的ZTD数据进行预测分析。结果表明，基于EEMD-SARIMA的ZTD改正预报模型能够满足不同地区、不同季节下的ZTD估计需求，是一种高精度的ZTD预报方法。  相似文献   

中蒙边界地区汇水域沉积物69种元素的背景值     

刘汉粮  聂兰仕  SHOJIN Davaa  王学求  迟清华 《地学前缘》2020,27(3):202-221

中蒙边界地区成矿地质条件优越,是世界上重要的金属成矿省和全球3大斑岩型铜(金、钼)成矿带之一,资源潜力巨大。中蒙合作1∶100万地球化学填图采集了海量的地球化学数据,为研究该地区元素分散富集、成矿趋势、资源评价和环境变化提供基础数据,为“一带一路”资源布局提供决策依据。以X±3S为临界值一次性剔除离群值后的数据集的中位值作为背景值的估计值,计算了中蒙边界地区12个Ⅱ级构造单元和5个Ⅱ级成矿省的汇水域沉积物69种元素背景值,探讨了中蒙边界地区汇水域沉积物69种元素背景值的区域分布规律和特征。研究表明不同的地质背景导致元素的地球化学分布模式不同,不同构造单元具有显著差异的元素地球化学特征,元素的海量聚集为大型矿床的形成提供了充足的元素供给,形成特定的地球化学省。这些背景值为进一步深入开发利用中蒙边界地球化学填图数据提供了可供对比的基础数据。  相似文献   

全球海潮模型最新进展及在中国沿海精度评估     

范长新 《大地测量与地球动力学》2019,39(5):476-481

介绍TPXO、FES、Chinatide、MIKE Global Tide、Utide等典型海潮模型，总结归纳其同化潮汐数据来源和最新的海洋地形数据，利用我国沿岸长期验潮站以外的26个中短期潮位观测站评估TPXO等海潮模型预报精度。结果表明，全球海潮模型对我国沿海M2分潮的预报精度普遍较低，且主导了几种海潮模型在中国海域的整体预报精度；相比MIKE Global Tide和TPXO7.2,TPXO8、TPXO_Yellow Sea 2010和TPXO_China&Ind模型在我国沿海的预报精度更高。  相似文献   

基于全球分布的地震观测数据估计0S0模态的特征频率及品质因子     

周丰森  王迪晋  旦增 《大地测量与地球动力学》2019,39(10):1013-1016

选取2011-03-11日本MW9.3地震后全球地震台站记录的约220 h波形数据，基于一定的判断准则，筛选出质量较高的448个垂向观测数据，采用频域AR方法对0S0模态的特征频率和品质因子进行估值，并以信噪比为权重进行加权平均，得到特征频率f=0.814 658 4±5.3×10-7，品质因子Q=5 586±12。该结果与已有研究成果相比精度更高，有助于约束现有地球介质密度和衰减模型，使其更接近真实地球。  相似文献   

云南武定县朱家坝尾矿库渗漏原因浅析     

周南  李卿  喻涌麒 《云南地质》2020,(1):118-124

位于云南省楚雄州武定县朱家坝新建尾矿库,在使用过程中,该尾矿库下游一泉水点出现尾矿粉渗漏污染,通过地质勘查,发现该尾矿库下伏昆阳群绿汁江组(Pt2lz)的白云岩基底,存在一隐伏断层,渗漏污染原因与该断层及其形成的岩溶裂隙有直接的关系。  相似文献