An Amended Chemical Mass Balance Model for Source Apportionment of PM2.5 in Typical Chinese Eastern Coastal Cities     

Qiaoli Wang  Nana Cheng  Sujing Li  Minli Dong  Xiangqian Wang  Linlin Ge  Tianjiao Guo  Wei Li  Xiang Gao 《洁净——土壤、空气、水》2019,47(2)

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基态位涡径向分布对浅水涡旋系统演变的影响分析Part Ⅱ:扰动发展和结构变化          下载免费PDF全文

刘爽  钟玮  刘宇迪 《地球物理学报》2018,61(9):3592-3606

本文在基态位涡（Potential Vorticity，PV）径向分布和基态涡旋强度对热带气旋（Tropical Cyclone，TC）类涡旋系统稳定性特征影响的研究基础上，结合理想试验和数值模拟诊断分析基态PV径向分布对扰动增长和系统结构变化的影响.基于线性正压浅水模型，设计三种典型基态PV中空结构下基态涡旋强度对系统稳定性影响的敏感性试验.结果表明：基态涡旋的强度主要影响稳定性的强弱，强度越强，不稳定增长率越大，而基态PV径向分布对系统最不稳定波动性质起着决定作用.分析不同波数下扰动的发展及不同波数间扰动的相互作用可知，对于宽且实的PV环，系统稳定性主要取决于低波数不稳定，且最不稳定波数扰动的发展具有明显的优势地位；对于窄且空的PV环，系统稳定性主要取决于高波数不稳定，且多个高波数下增长最快模态的不稳定增长率值十分接近.利用模态线性叠加法讨论扰动增长对系统结构变化的影响表明：最不稳定波数的扰动发展对系统结构变化有关键影响，而多个波数的扰动不稳定增长相当时，不同波数的扰动发生相互作用从而影响系统结构变化.最后，利用实际个例模拟资料分析基态PV径向分布及其变化对TC结构和强度的影响表明：TC内核区出现的多边形眼墙结构与当前时刻基态PV径向分布所决定的最不稳定波数有很好的对应关系，同时基态PV径向分布变化所反映出的系统动力稳定性强弱与TC强度发展阶段具有很好的相关性.  相似文献   

Moving from plot-based to hillslope-scale assessments of savanna vegetation structure with long-range terrestrial laser scanning (LR-TLS)     

《International Journal of Applied Earth Observation and Geoinformation》2020

Reliable quantification of savanna vegetation structure is critical for accurate carbon accounting and biodiversity assessment under changing climate and land-use conditions. Inventories of fine-scale vegetation structural attributes are typically conducted from field-based plots or transects, while large-area monitoring relies on a combination of airborne and satellite remote sensing. Both of these approaches have their strengths and limitations, but terrestrial laser scanning (TLS) has emerged as the benchmark for vegetation structural parameterization – recording and quantifying 3D structural detail that is not possible from manual field-based or airborne/spaceborne methods. However, traditional TLS approaches suffer from similar spatial constraints as field-based inventories. Given their small areal coverage, standard TLS plots may fail to capture the heterogeneity of landscapes in which they are embedded. Here we test the potential of long-range (>2000 m) terrestrial laser scanning (LR-TLS) to provide rapid and robust assessment of savanna vegetation 3D structure at hillslope scales. We used LR-TLS to sample entire savanna hillslopes from topographic vantage points and collected coincident plot-scale (1 ha) TLS scans at increasing distances from the LR-TLS station. We merged multiple TLS scans at the plot scale to provide the reference structure, and evaluated how 3D metrics derived from LR-TLS deviated from this baseline with increasing distance. Our results show that despite diluted point density and increased beam divergence with distance, LR-TLS can reliably characterize tree height (RMSE = 0.25–1.45 m) and canopy cover (RMSE = 5.67–15.91%) at distances of up to 500 m in open savanna woodlands. When aggregated to the same sampling grain as leading spaceborne vegetation products (10–30 m), our findings show potential for LR-TLS to play a key role in constraining satellite-based structural estimates in savannas over larger areas than traditional TLS sampling can provide.  相似文献   

Strong variation in weathering of layered rock maintains hillslope‐scale strength under high precipitation          下载免费PDF全文

Jennifer Von Voigtlander  Marin K. Clark  Dimitrios Zekkos  William W. Greenwood  Suzanne P. Anderson  Robert S. Anderson  Jonathan W. Godt 《地球表面变化过程与地形》2018,43(6):1183-1194

The evolution of volcanic landscapes and their landslide potential are both dependent upon the weathering of layered volcanic rock sequences. We characterize critical zone structure using shallow seismic V_p and V_s profiles and vertical exposures of rock across a basaltic climosequence on Kohala peninsula, Hawai’i, and exploit the dramatic gradient in mean annual precipitation (MAP) across the peninsula as a proxy for weathering intensity. Seismic velocity increases rapidly with depth and the velocity–depth gradient is uniform across three sites with 500–600 mm/yr MAP, where the transition to unaltered bedrock occurs at a depth of 4 to 10 m. In contrast, velocity increases with depth less rapidly at wetter sites, but this gradient remains constant across increasing MAP from 1000 to 3000 mm/yr and the transition to unaltered bedrock is near the maximum depth of investigation (15–25 m). In detail, the profiles of seismic velocity and of weathering at wet sites are nowhere monotonic functions of depth. The uniform average velocity gradient and the greater depths of low velocities may be explained by the averaging of velocities over intercalated highly weathered sites with less weathered layers at sites where MAP > 1000 mm/yr. Hence, the main effect of climate is not the progressive deepening of a near‐surface altered layer, but rather the rapid weathering of high permeability zones within rock subjected to precipitation greater than ~1000 mm/yr. Although weathering suggests mechanical weakening, the nearly horizontal orientation of alternating weathered and unweathered horizons with respect to topography also plays a role in the slope stability of these heterogeneous rock masses. We speculate that where steep, rapidly evolving hillslopes exist, the sub‐horizontal orientation of weak/strong horizons allows such sites to remain nearly as strong as their less weathered counterparts at drier sites, as is exemplified by the 50°–60° slopes maintained in the amphitheater canyons on the northwest flank of the island. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

顾及局部与结构特征的稀疏多项式逻辑回归高光谱图像分类方法     

沈宇臻  官云兰  杨禄  刘承承  严小芳 《测绘通报》2019,(6):24-28

稀疏多项式逻辑回归在分类中仅利用图像光谱信息，导致分类效果不太理想。本文提出了一种顾及局部与结构特征的稀疏多项式逻辑回归高光谱图像分类方法。首先利用加权均值滤波与拓展形态学多属性剖面对原始高光谱图像进行局部与结构特征提取；然后对二者进行加权平均特征级融合以获取更具唯一性的像元特征；最后由稀疏多项式逻辑回归分类器对融合结果进行分类。结果表明，本文方法能有效地提高分类精度，而且具有较强的稳健性。  相似文献   

北京怀柔云蒙山地区花岗岩风化过程的地球化学基因     

王旭阳  姚宁  龚庆杰  晁岳德  彭程  吴媛 《地学前缘》2021,28(1):363-374

地球化学基因是近两年提出的一种新的地球化学示踪技术,本文选择北京怀柔云蒙山地区两个邻近的花岗岩风化剖面(编号为B和C)来分析岩性地球化学基因和金矿化地球化学基因的属性特征。剖面B样品的化学蚀变指数CIA变化为51.3~58.9,WIG的范围为89.4~68.6,属于初始风化程度;剖面C样品的CIA变化为52.4~78.4,WIG的范围为84.8~25.3,属于中等风化程度。这种邻近剖面风化程度的明显差异表明微环境对岩石风化产物的影响是显著的。相对于剖面底部新鲜花岗岩而言,岩性地球化学基因相似度在剖面B和C中的范围分别为85%~100%和90%~100%,金矿化地球化学基因相似度范围分别为85%~100%和80%~100%。当相对于剖面顶部土壤样品时,岩性地球化学基因相似度在剖面B和C中的范围分别为80%~100%和90%~100%,金矿化地球化学基因相似度范围分别为85%~100%和80%~100%。依据≥80%的基因相似度标准(区分基因是否相似),尽管两个剖面在风化程度上存在明显差异,但岩性地球化学基因和金矿化地球化学基因在两个剖面内部均表现出良好的遗传性和继承性,且在两个剖面之间体现出同源风化产物之间具有良好的相似性。相对于理想金矿石(其金矿化基因为12020202020)而言,金矿化相似度在剖面B和C中的范围分别为25%~50%和30%~50%。依据≥40%的金矿化相似度(即样品与理想金矿石的金矿化相似度)作为存在金矿化异常的标准,在两个剖面中均可识别出厚度约1 m左右的矿化异常层位。因此,金矿化基因除了具有地球化学基因的属性(遗传性、继承性、相似性)外,其金矿化相似度(即相对于理想金矿石的相似度)也有可能作为金矿勘查中的一个地球化学综合指标。  相似文献   

利用TRMM PR和IGRA探测分析的拉萨降水云内大气温湿廓线特征     

王梦晓  王瑞  傅云飞 《高原气象》2019,38(3):539-551

利用热带测雨卫星测雨雷达(TRMM PR)降水回波反射率因子廓线(降水率廓线)与全球探空大气温湿廓线(IGRA)的多年融合资料,研究了青藏高原拉萨站夏季降水结构及相应的大气温湿结构特征。结果表明,该站降水回波反射率因子分布在17~45 dBz,大部分小于26 dBz;回波顶高度达17 km,呈现“瘦高”外形;相应的大气低层湿润,降水云内大气并非饱和,但温度露点差比全部状态时的值小。深厚降水系统的回波外形也呈现“瘦高”,按照降水率随高度的非线性变化,其垂直结构可分为三层,而浅薄降水系统的垂直结构呈现一层,即平均降水率斜率随高度呈对数线性变化,最大平均降水率(0.7 mm·h^-1)出现在地面。深厚降水与浅薄降水云体内400 hPa高度(7.5 km)上下的露点温度递减的速率不同。降水云体内的零度层高度大约6.3 km,但PR没有探测到零度层亮带。统计结果还表明拉萨探空站及附近的大气可降水量为20.89 mm·d^-1,降水转化率为27.0%,深厚降水系统的降水转化率是浅薄降水系统的2.9倍,深厚降水系统和浅薄降水系统的CAPE值分别为1941.7 J·kg^-1和1451.8 J·kg^-1。本研究结果为模式模拟青藏高原降水云内的温湿结构提供了观测依据。  相似文献   

登陆台风边界层风廓线特征的地基雷达观测   总被引：2，自引：0，他引：2  

赵坤  王明筠  朱科锋  明杰  马秀梅  王元 《气象学报》2015,73(5):837-852

为了分析登陆台风边界层风廓线特征,利用2004—2013年中国东南沿海新一代多普勒天气雷达收集的17个登陆台风资料,采用飓风速度体积分析方法,反演登陆台风的边界层风场结构特征。与探空观测对比表明,利用雷达径向风场可以准确地反演登陆台风的边界层风场结构,其风速误差小于2 m/s,风向误差小于5°。所有登陆台风合成的边界层风廓线显示,在近地层(100 m)以上,边界层风廓线存在类似急流的最大切向风,其高度均在1 km以上,显著高于大西洋观测到的飓风边界层急流高度(低于1 km)。陆地边界层内低层入流强度也明显大于过去海上观测,这主要是由陆地上摩擦增大引起。越靠近台风中心,边界层风廓线离散度越大,其中,径向风廓线比全风速以及切向风廓线离散度更大。将风廓线相对台风移动方向分为4个象限,分析边界层风廓线非对称特征显示,台风移动前侧入流层明显高于移动后侧。最大切向风位于台风移动左后侧,而台风右后侧没有显著的急流特征,与过去理想模拟的海陆差异导致的台风非对称分布特征一致。  相似文献   

Distribution of Palaeozoic tectonic superimposed unconformities in the Tarim Basin,NW China: significance for the evolution of palaeogeomorphology and sedimentary response     

Hao Liu  Ian D. Somerville  Changsong Lin  Shengjie Zuo 《Geological Journal》2016,51(4):627-651

Seismic and drilling well data were used to examine the occurrence of multiple stratigraphic unconformities in the Tarim Basin, NW China. The Early Cambrian, the Late Ordovician and the late Middle Devonian unconformities constitute three important tectonic sequence boundaries within the Palaeozoic succession. In the Tazhong, Tabei, Tadong uplifts and the southwestern Tarim palaeo‐uplift, unconformities obviously belong to superimposed unconformities. A superimposed unconformity is formed by superimposition of unconformities of multiple periods. Areas where superimposed unconformities develop are shown as composite belts of multiple tectonic unconformities, and as higher uplift areas of palaeo‐uplifts in palaeogeomorphologic units. The contact relationship of unconformities in the lower uplift areas is indicative of truncation‐overlap. A slope belt is located below the uplift areas, and the main and secondary unconformities are characterized by local onlap reflection on seismic profiles. The regional dynamics controlled the palaeotectonic setting of the Palaeozoic rocks in the Tarim Basin and the origin and evolution of the basin constrained deposition. From the Sinian to the Cambrian, the Tarim landmass and its surrounding areas belonged to an extensional tectonic setting. Since the Late Ordovician, the neighbouring north Kunlun Ocean and Altyn Ocean was transformed from a spreading ocean basin to a closed compressional setting. The maximum compression was attained in the Late Ordovician. The formation of a tectonic palaeogeomorphologic evolution succession from a cratonic margin aulacogen depression to a peripheral foreland basin in the Early Caledonian cycle controlled the deposition of platform, platform margin, and deep‐water basin. Tectonic uplift during the Late Ordovician resulted in a shallower basin which was followed by substantial erosion. Subsequently, a cratonic depression and peripheral or back‐arc foreland basin began their development in the Silurian to Early–Middle Devonian interval. In this period, the Tabei Uplift, the Northern Depression and the southern Tarim palaeo‐uplift showed obvious control on depositional systems, including onshore slope, shelf and deep‐water basin. The southern Tarim Plate was in a continuous continental compressional setting after collision, whereas the southern Tianshan Ocean began to close in the Early Ordovician and was completely closed by the Middle Devonian. At the same time, further compression from peripheral tectonic units in the eastern and southern parts of the Tarim Basin led to the expansion of palaeo‐uplift in the Late Devonian–Early Carboniferous interval, and the connection of the Tabei Uplift and Tadong Uplift, thus controlling onshore, fluvial delta, clastic coast, lagoon‐bay and shallow marine deposition. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

梯度电测深剖面法及其应用     

葛为中  吕玉增  丁云河 《物探与化探》2011,35(2):206-211

针对常规直流电测深的应用情况,改革布极方式,研究提出梯度测深剖面法。该法能简化布极工序,可用多台接收机或多通道电测仪在多个电测深点上同时(连续)观测,大大提高工作效率。其装置有三极测深、四极测深和中梯测深等,其观测剖面上由于采用供电极稀设方式,能很好地适应二维正反演计算网格,宜于获得带地形的电阻率、极化率断面,实现电测深数据的层折成像。目前,该梯度测深方法已应用于金属矿勘查和工程勘察之中,取得成效。  相似文献