科尔沁湿草甸参考作物蒸散发模拟分析     

李霞  刘廷玺  段利民  王冠丽  童新  周亚军  杨晓君 《中国沙漠》2020,40(2):134-143

为探明气候变化下干旱半干旱地区湿草甸参考作物蒸散发(ET₀)影响因子,使用FAO 56 P-M模型对科尔沁湿草甸ET₀进行模拟,利用涡度相关系统对模型的适用性进行评价,并通过通径分析及指标敏感性分析对ET₀的影响因子进行辨识。结果表明:(1)小时尺度模拟精度最高,日尺度次之,月尺度较差,小时尺度上晴、阴、雨3种天气条件下模拟效果不同,晴天最优,阴雨天较差。(2)ET₀年内变化呈单峰曲线状,生长季明显高于非生长季,集中在3—10月,占全年89.79%。生长季典型晴天ET₀逐小时分布特征遵循倒“U”单峰型变化规律。(3)通径分析结果显示,对ET₀的通径系数以及对回归方程估测可靠程度E的总贡献均表现为VPD(饱和水汽压差) > T_min(最低气温) > R_n(冠层表面净辐射)>u₂(2 m高度风速),即VPD为影响ET₀最重要的因子;指标敏感性分析中,在去除VPD后引起的E变化最大,说明ET₀对VPD的变化最为敏感,其次为u₂、T_min和R_n。  相似文献   

Jason-2高度计电离层GIM误差分析及修正研究     

黄霞凤  苗洪利  苗翔鹰  薛文文 《海洋学报》2019,41(7):143-148

基于Jason-2高度计2015年地球物理数据集(GDR)38个周期太平洋海域的全球电离层图(GIM)电离层校正值和双频校正值的数据，分不同季度和不同纬度区域比较二者的差异，结果表明:GIM值与双频校正值之间存在明显的差异，GIM校正值普遍高于双频校正值，说明GIM高估了电离层路径延迟，GIM校正值与双频校正值的差异与季节和纬度区间有关。用梯度下降法得到GIM值的修正方程，将修正方程应用于2016年Jason-2的全年数据，修正后的GIM值与双频校正值十分接近，在各年份中均具有良好的适用性。在单频高度计不能使用电离层双频校正算法的情况下，可以利用不同季度和不同纬度区域的修正方程对同等高度的高度计GIM值进行修正以达到双频校正值的精度水平。  相似文献   

隐伏正断层错动致地表破裂变形特征的研究     

齐剑峰  郝文拯  王晓明  张江伟 《震灾防御技术》2019,14(3):628-639

通过建立三维计算模型，对隐伏正断层在均匀错动、倾斜错动和翘倾错动方式下地表土体的应力路径、破裂和变形特征进行了研究。根据地表破裂临界值，分析了工程建设“避让带”的宽度和起始位置的变化特征。根据行业规范，提出工程建设“关注带”的确定方法，分析了“关注带”的宽度和起始位置的变化特征，得到以下主要结论:①在断层错动过程中，位于两侧的地表土体应力路径变化明显不同，下盘一侧和上盘一侧分别以三轴拉伸和三轴压缩为主；②地表强变形带与地表破裂带的分布并不一致，需要综合考虑等效塑性应变和总位移比2个指标来评价同震地表错动对建筑物的影响；③当隐伏断层错动的垂直位移达到3m时，工程建设“避让带”的宽度在10—90m范围内变化，受上覆土体厚度和断层倾角的影响最大，而工程建设“关注带”的宽度在150—400m范围内变化，受上覆土体的性质影响最大。  相似文献   

基于分布式控制力矩陀螺的水下航行器轨迹跟踪控制   总被引：2，自引：0，他引：2  

黄道敏  徐瑞昆  唐国元  冯雷  刘智  徐国华 《海洋工程》2018,36(6):69-76

基于控制力矩陀螺群(CMGs)的水下航行器具有低速或零速机动的能力。采用基于分布式CMGs的水下航行器方案,并研究其水平面的轨迹跟踪控制问题。通过全局微分同胚变换将非完全对称的动力学模型解耦成标准欠驱动控制模型,并根据简化的模型构建其轨迹跟踪的误差动力学模型,将轨迹跟踪控制问题转化为误差模型镇定问题。基于一种分流神经元模型和反步法设计了系统的轨迹跟踪控制律,该控制器不需要对任何虚拟控制输入进行求导计算,且能确保跟踪误差的最终一致有界性。仿真结果表明该控制器能够实现在不依赖动力学参数先验知识的情况下对光滑轨迹的有效跟踪。  相似文献   

Metamorphism and geochronology of garnet amphibolite from the Beishan Orogen,southern Central Asian Orogenic Belt:Constraints from P-T path and zircon U-Pb dating     

《地学前缘(英文版)》2020,11(4):1189-1201

Numerous lenses of garnet amphibolite occur in the garnet-bearing biotite-plagioclase gneiss belt in the Baishan area of the Beishan Orogen,which connects the Tianshan Orogen to the west and the Mongolia-Xing'anling Orogen to the east.The study of metamorphism in Beishan area is of great significance to explain the tectonic evolution of Beishan orogen.According to the microstructures,mineral relationships,and geothermobarometry,we identified four stages of mineral assemblages from the garnet amphibolite sample:(1) a pre-peak stage,which is recorded by the cores of garnet together with core-inclusions of plagioclase(Pl_1);(2) a peak stage,which is recorded by the mantles of garnet together with mantle-inclusions of plagioclase(Pl_2)+amphibole(Amp_1)+Ilmenite(Ilm_1)+biotite(Bt_1),developed at temperature-pressure(P-T) conditions of 818.9-836.5℃ and7.3-9.2 kbar;(3) a retrograde stage,which is recorded by garnet rims + plagioclase(Pl_3)+amphibole(Amp_2)+orthopyroxene(Opx_1)+biotite(Bt_2)+Ilmenite(Ilm_2),developed at P-T conditions of 796.1-836.9℃ and5.6-7.5 kbar;(4) a symplectitic stage,which is recorded by plagioclase(Pl_4)+orthopyroxene(Opx_2)+amphibole(Amp_3)+biotite(Bt_3) symplectites,developed at P-T conditions of 732 ±59.6℃ and 6.1 ±0.6 kbar.Moreover,the U-Pb dating of the Beishan garnet amphibolite indicates an age of 301.9 ±4.7 Ma for the protolith and 281.4±8.5 Ma for the peak metamorphic age.Therefore,the mineral assemblage,P-T conditions,and zircon U-Pb ages of the Beishan garnet amphibolite define a near-isothermal decompression of a clockwise P-T-t(Pressure-Temperature-time) path,indicating the presence of over thickened continental crust in the Huaniushan arc until the Early Permian,then the southern Beishan area underwent a process of thinning of the continental crust.  相似文献   

Water transport and tracer mixing in volcanic ash soils at a tropical hillslope: A wet layered sloping sponge     

Giovanny M. Mosquera  Patricio Crespo  Lutz Breuer  Jan Feyen  David Windhorst 《水文研究》2020,34(9):2032-2047

Andosol soils formed in volcanic ash provide key hydrological services in montane environments. To unravel the subsurface water transport and tracer mixing in these soils we conducted a detailed characterization of soil properties and analyzed a 3-year data set of sub-hourly hydrometric and weekly stable isotope data collected at three locations along a steep hillslope. A weakly developed (52–61 cm depth), highly organic andic (Ah) horizon overlaying a mineral (C) horizon was identified, both showing relatively similar properties and subsurface flow dynamics along the hillslope. Soil moisture observations in the Ah horizon showed a fast responding (few hours) “rooted” layer to a depth of 15 cm, overlying a “perched” layer that remained near saturated year-round. The formation of the latter results from the high organic matter (33–42%) and clay (29–31%) content of the Ah horizon and an abrupt hydraulic conductivity reduction in this layer with respect to the rooted layer above. Isotopic signatures revealed that water resides within this soil horizon for short periods, both at the rooted (2 weeks) and perched (4 weeks) layer. A fast soil moisture reaction during rainfall events was also observed in the C horizon, with response times similar to those in the rooted layer. These results indicate that despite the perched layer, which helps sustain the water storage of the soil, a fast vertical mobilization of water through the entire soil profile occurs during rainfall events. The latter being the result of the fast transmissivity of hydraulic potentials through the porous matrix of the Andosols, as evidenced by the exponential shape of the water retention curves of the subsequent horizons. These findings demonstrate that the hydrological behavior of volcanic ash soils resembles that of a “layered sponge,” in which vertical flow paths dominate.  相似文献   

TRANSIT: a GIS toolbox for estimating the duration of ancient sail-powered navigation     

Gianmarco Alberti 《制图学和地理信息科学》2018,45(6):510-528

Cost-surface analysis in Geographic Information System (GIS) environment has been less frequently used in the study of ancient sail navigation than in other studies of the human past. Navigation cost-surface analysis entails the use of GIS tools that are versatile but not very easy to grasp and to put to work. This article describes an ArcGIS toolbox built to facilitate cost-surface analysis of ancient sail navigation. It estimates the navigation time from a start location, considering parameters relevant for the generation of an accumulated anisotropic cost-surface, automating the complex workflow required to meaningfully pre- and post-process the data. Acknowledging the limitations inherent to the tool, and to the modeling of a complex matter such as sail navigation, the toolbox is first described and then used in a worked example. Historically recorded voyages in the Mediterranean during classical antiquity are compared to estimated durations generated by the toolbox. In spite of structural and expected limitations, the results indicate that the proposed toolbox may produce reasonable estimates. These should be thought of as values gravitating around, not matching, likely past durations. The estimated values may prove useful as an indication of the order of magnitude of past voyages’ duration, and as frame of reference in measuring ancient maritime space through time.  相似文献   

基于LEAP模型的城市交通低碳发展路径研究——以广州市为例     

黄莹  郭洪旭  廖翠萍  赵黛青 《气候变化研究进展》2019,15(6):670-683

以广州市为例,应用长期能源替代规划系统（LEAP）模型,通过设置政策情景、低碳情景和绿色低碳情景,模拟不同发展情景下广州交通领域未来的能源消费需求和CO₂排放趋势,分析城市低碳发展的方向和路径。结果显示,随着城镇化进程的加快和生产生活运输需求的增加,广州交通领域碳排放总量将持续增长,但增长速度有所放缓。政策情景下,广州交通领域的CO₂排放将于2035年左右达到峰值,严重滞后于广州市提出的碳排放总量达峰目标;低碳和绿色低碳情景下,通过加大低碳政策措施的力度,达峰时间有望分别提前到2025年和2023年。要实现城市交通的低碳发展,促进交通碳排放提前达峰,需要大力发展铁路和水路运输,全面落实公交优先发展战略,有效控制小汽车数量和出行频率,不断提高交通工具的清洁化和能效水平,逐步形成各种运输方式协调发展的综合交通运输体系,推动城市交通低碳发展。  相似文献   

台风“尤特”登陆后复杂路径的环境场特征   总被引：1，自引：0，他引：1       下载免费PDF全文

覃武  罗小莉  钟利华  林宗桂  林开平  林墨 《气象与环境科学》2019,42(1):110-118

台风"尤特"(1311)2013年8月13—19日登陆减弱后直达桂东北并停留打转,其后又转向西南移动,"尤特"残涡在广西境内生存活动了112 h,造成了大范围强降雨。使用常规与非常规观测资料,研究了"尤特"登陆后的环境场与其长生命期及复杂移动路径的关系。结果发现:"尤特"登陆北上阶段主要受大尺度环境场的引导气流主导,后因引导气流转向减弱,与变压梯度力近似达到平衡导致停留打转;南下弱冷空气卷入与西南气流辐合形成负变压槽,负变压槽中风向气旋性切变产生正涡度效应向"尤特"残涡输送,与西南气流充沛的水汽输送共同作用使"尤特"残涡得以长时间维持。弱冷空气卷入使中尺度变压场中的正变压加强,在变压梯度力与引导气流共同作用下,"尤特"残涡沿负变压槽向西南移动。  相似文献   

关于巴罗式变质带的最新研究及其对研究秦岭杂岩的意义   总被引：1，自引：1，他引：0  

任留东  李崇  王彦斌  李淼 《岩石学报》2018,34(4):913-924

本文对苏格兰高地Grampian造山运动中产生的经典巴罗变质带进行了讨论,重点介绍了近年来关于其变质作用的特征及发生机制认识方面的重大变化。强调巴罗变质作用仅发生在整个造山运动过程中的部分时段,纪录了短暂的加热过程,时空上与区域内大规模的双峰式岩浆活动有关。经典的巴罗变质系列并非形成于地壳增厚及其热弛豫,而是代表了中地壳内大规模的接触变质作用。参考经典地区的变质特征,对发育巴罗式变质作用的秦岭杂岩进行了初步对比分析,指出其中与夕线石有关的变质P-T-t轨迹可能是等压冷却过程,而不是等温降压的顺时针演化模式。秦岭杂岩的变质作用时间仍需要进一步准确厘定。结合其它相关地质特征的分析和对比,得出如下推论:巴罗式变质带发育地区的变质作用、混合岩与花岗岩均属于同一动力系统作用的结果,花岗质岩体不是变质作用的原因;基性岩浆可能提供了巴罗式变质作用发生所需要的热能,但不是必要条件;巴罗式变质作用可以发生在正常地壳厚度情况下,不是碰撞构造的标志;伴随热异常的变形过程中产生了变质带的梯度分布(巴罗式变质带)和一些花岗岩,形成类似于底辟的冲起构造。  相似文献