利用MERRA-2地表温压资料进行中国区域GNSS水汽反演的精度分析北大核心CSCD

为分析美国宇航局发布的最新MERRA-2再分析资料地表温压产品在中国区域进行GNSS水汽反演的精度,联合中国区域609个地面气象站实测温度和气压数据、48个GNSS站及并址探空站资料,评估MERRA-2温压产品及其在GNSS PWV反演中的精度。结果表明:1)MERRA-2气压和温度年均bias分别为-0.01 hPa和0.38 K,年均RMSE分别为1.08 hPa和2.66 K,MERRA-2再分析资料温压产品在中国区域具有较高的精度;2)MERRA-2再分析资料温压产品在中国大部分地区呈现负偏差,精度从高到低依次为南方地区、北方地区、西北地区和青藏高原地区;3)将MERRA-2温压产品的PWV反演结果与并址探空站实测PWV进行对比可知,MERRA-2再分析资料温压产品反演的GNSS PWV平均RMSE为2.16 mm,能较好地反映PWV的日变化。因此,MERRA-2地表温压产品在中国区域的气象研究及GNSS水汽监测中具有重要意义。     

考虑桩周土竖向作用大直径楔形桩纵向振动特性

将桩土系统划分为数量足够多的微元段,相邻微元桩段接触面处的环形凸面与土的相互作用采用单个Voigt体模拟,求得Voigt体的弹簧和黏壶系数。结合相邻微元桩段接触面上的应力平衡条件和位移连续条件,得到修正的阻抗函数递推法,桩身采用Rayleigh杆考虑桩身的横向惯性效应。结合桩底的边界条件,运用拉普拉斯变换和修正的阻抗函数递推法求得了平面应变条件下成层土中考虑桩周土竖向作用时大直径楔形桩桩顶复阻抗的解析解。通过与已有解对比,研究了桩周土竖向作用对桩顶复刚度和桩顶在瞬态激振下的速度响应的影响,并在低频域内详细分析了桩周土的竖向作用与桩土系统参数对桩顶复刚度的影响的耦合作用。     

Fred’s Flow (Canada) and Murphy Well (Australia): thick komatiitic lava flows with contrasting compositions,emplacement mechanisms and water contents

Two Archaean komatiitic flows, Fred’s Flow in Canada and the Murphy Well Flow in Australia, have similar thicknesses (120 and 160 m) but very different compositions and internal structures. Their contrasting differentiation profiles are keys to determine the cooling and crystallization mechanisms that operated during the eruption of Archaean ultramafic lavas. Fred’s Flow is the type example of a thick komatiitic basalt flow. It is strongly differentiated and consists of a succession of layers with contrasting textures and compositions. The layering is readily explained by the accumulation of olivine and pyroxene in a lower cumulate layer and by evolution of the liquid composition during downward growth of spinifex-textured rocks within the upper crust. The magmas that erupted to form Fred’s Flow had variable compositions, ranging from 12 to 20 wt% MgO, and phenocryst contents from 0 to 20 vol%. The flow was emplaced by two pulses. A first ~20-m-thick pulse was followed by another more voluminous but less magnesian pulse that inflated the flow to its present 120 m thickness. Following the second pulse, the flow crystallized in a closed system and differentiated into cumulates containing 30–38 wt% MgO and a residual gabbroic layer with only 6 wt% MgO. The Murphy Well Flow, in contrast, has a remarkably uniform composition throughout. It comprises a 20-m-thick upper layer of fine-grained dendritic olivine and 2–5 vol% amygdales, a 110–120 m intermediate layer of olivine porphyry and a 20–30 m basal layer of olivine orthocumulate. Throughout the flow, MgO contents vary little, from only 30 to 33 wt%, except for the slightly more magnesian basal layer (38–40 wt%). The uniform composition of the flow and dendritic olivine habits in the upper 20 m point to rapid cooling of a highly magnesian liquid with a composition like that of the bulk of the flow. Under equilibrium conditions, this liquid should have crystallized olivine with the composition Fo94.9, but the most magnesian composition measured by electron microprobe in samples from the flow is Fo92.9. To explain these features, we propose that the parental liquid contained around 32 wt% MgO and 3 wt% H₂O. This liquid degassed during the eruption, creating a supercooled liquid that solidified quickly and crystallized olivine with non-equilibrium textures and compositions.     

Temporally stable patterns but seasonal dependent controls of soil water content: Evidence from wavelet analyses

Scale‐ and location‐dependent relationships between soil water content (SWC) and individual environmental factors have been widely explored. SWC is controlled by multiple factors concurrently; however, the multivariate relationship is rarely explored at different scales and locations. Multivariate controls of SWC at different scales and locations in two seasons within a hummocky landscape of North America were identified using bivariate wavelet coherency and multiple wavelet coherence. Results showed that depth to CaCO₃ layer, which was correlated with elevation over all locations at scales of 36–144 m and cos(aspect), provided the best individual factor for explaining SWC variations in spring (May 2) and summer (August 23), respectively. Although spatial patterns of SWC were temporally stable, different topographic indices affected spatial distribution of SWC in different seasons (elevation in spring and aspect in summer) due to different dominating hydrological processes. These varying hydrological processes also resulted in the distinct role of soil organic carbon (SOC) content in different seasons: a positive correlation in spring and a negative correlation in summer. Multiple wavelet coherence identified a combination of depth to CaCO₃ layer and SOC in spring and a combination of cos(aspect) and SOC in summer that controlled SWC at different scales and locations, respectively. This indicated a combined effect of soil and topographic properties on SWC distribution and a clear need for these two factors in developing scale‐dependent prediction of SWC in the hummocky landscape of North America.     

基于Noah-LSM模式和CoLM模式的青藏高原中部陆面过程模拟

利用中国科学院那曲高寒气候环境观测研究站Amdo站2012年10月1日-2013年10月1日的气象和土壤资料,通过Noah-LSM模式和CoLM模式对青藏高原中部陆面过程进行模拟研究。模拟结果表明：两个模式对辐射通量的模拟均与观测值较吻合,地表长波辐射的模拟效果最好,净辐射次之,地表反射辐射最差;两个模式模拟的土壤温度与观测值很接近,均是表层的模拟效果好于深层,夏季的模拟效果好于冬季;土壤的冻结和融化过程都是由表层开始向下延伸的,CoLM模式模拟的冻融起止时间与观测值更为接近;两个模式对土壤湿度的变化趋势模拟较好,但存在较大偏差。     

地理信息服务语义标注原理与关键技术及应用

随着地理信息服务应用领域和受众群体的日益广泛,人们对地理信息服务的需求越来越多元化。一方面网络上注册和发布的地理信息服务的数量急剧增长;另一方面人们对如何高效发现兴趣服务、组合兴趣服务以满足兴趣需要却常感到困惑。当前,用户只能通过关键字搜索并结合空间过滤条件查询OGC(Open Geospatial Consortium)的目录服务,来发现所需的数据和服务。用户在受益于目录服务带来的资源搜索便捷的同时,经常受到查全率和查准率不高的困扰。面对日益庞大的服务群,如何自动、快速、准确地发现目标服务,成为影响地理信息服务进一步发展与应用的瓶颈。本文围绕地理信息服务语义标注原理方法与关键技术展开研究,通过引入信息检索技术和语义网技术、语义服务技术,从面向地理信息服务语义标注的本体建模、基于地理概念匹配的语义标注算法、融合相似性度量与包含性推理的语义匹配与服务发现,以及语义标注和服务匹配质量评价方法4个方面进行了深入研究。针对地理概念半自动语义标注新算法、地理信息服务语义发现与匹配方法、服务语义标注和服务匹配质量评价、应用试验等具体研究内容进行了实验设计,并给出了需解决的核心问题,为当前地理信息服务匹配方法提供了新思路。     

Radiation belt electron acceleration induced by gyroresonant interaction with magnetosonic waves

Using Cluster 4 satellite data, we examine activities of fast magnetosonic (MS) waves in the outer radiation belt near the location L=4.2 on 28 May 2005. We adopt a Gaussian distribution to fit the observed power spectral density of MS waves and find the fitting wave strength to be 245 pT. We then calculate the bounce-averaged diffusion coefficients and show that these diffusion coefficients are pronounced within a region of pitch angles about 25°–70°. By solving a 2D Fokker-Planck diffusion equation, we simulate the dynamic evolution of the electron phase space density (PSD), and demonstrate that significant increases in electron PSDs at energies of MeVs occur mainly within the aforementioned pitch-angle range over a time scale of several hours. The current results suggest that the interaction between MS waves and electrons could be an important mechanism of electron acceleration in the radiation belt.     

三轴水泥土搅拌加固地基的应用与控制

文章阐述了三轴深层水泥土搅拌加固桩在浦东机场地道工程中的应用情况,并针对深层水泥土搅拌桩各个施工环节,提出了相应的质量控制措施.     

事件计时器在卫星激光测距中的应用

传统时间间隔的测量速率受限于被测事件的时间间隔，事件计时概念的引入可以很好地提高测量速率。事件计时器是高重频（kHz级）卫星激光测距（SLR）技术的主要设备。该文介绍了事件计时器A032．ET的性能以及其在卫星激光测距中的应用，为我国开展高重频SLR研究提供了技术支持。