基于VB.NET的地形图编号查询与面积计算程序

主要介绍利用Microsoft Visual Basic.NET编写的地形图分幅编号查询与面积计算程序。通过该程序,根据经纬度坐标或高斯坐标,可查询该点所在各种基本比例尺下的图幅编号、西南图廓点的经纬度坐标以及在不同坐标系下的图幅面积。     

Temporal and Spatial Variations of the Aerodynamic Roughness Length in the Ablation Zone of the Greenland Ice Sheet

To understand the response of the Greenland ice sheet to climate change the so-called ablation zone is of particular importance, since it accommodates the yearly net surface ice loss. In numerical models and for data analysis, the bulk aerodynamic method is often used to calculate the turbulent surface fluxes, for which the aerodynamic roughness length (z ₀) is a key parameter. We present, for the first time, spatial and temporal variations of z ₀ in the ablation area of the Greenland ice sheet using year-round data from three automatic weather stations and one eddy-correlation mast. The temporal variation of z ₀ is found to be very high in the lower ablation area (factor 500) with, at the end of the summer melt, a maximum in spatial variation for the whole ablation area of a factor 1000. The variation in time matches the onset of the accumulation and ablation season as recovered by sonic height rangers. During winter, snow accumulation and redistribution by snow drift lead to a uniform value of z ₀≈ 10⁻⁴ m throughout the ablation area. At the beginning of summer, snow melt uncovers ice hummocks and z ₀ quickly increases well above 10⁻² m in the lower ablation area. At the end of summer melt, hummocky ice dominates the surface with z ₀ > 5  ×  10⁻³ m up to 60 km from the ice edge. At the same time, the area close to the equilibrium line (about 90 km from the ice edge) remains very smooth with z ₀ = 10⁻⁵ m. At the beginning of winter, we observed that single snow events have the potential to lower z ₀ for a very rough ice surface by a factor of 20 to 50. The total surface drag of the abundant small-scale ice hummocks apparently dominates over the less frequent large domes and deep gullies. The latter results are verified by studying the individual drag contributions of hummocks and domes with a drag partition model.     

Solar Wind Effects Associated with a Recurrent,High-Latitude Coronal Brightness Enhancement

During the descent of Ulysses following the 2001 solar north pole passage, the SOHO LASCO C2 telescope recorded a particularly strong sequence of recurrent polarization brightness (pB) features at latitudes of around 55°. As Ulysses passed overhead, solar rotation swept the interplanetary extensions of these persistent coronal structures over the spacecraft. Comparison of solar remote sensing and Ulysses in situ observations through 2002 reveals the solar wind effects of very bright and recurrent K-coronal structures at high solar latitudes and of a steeply inclined heliospheric neutral sheet (HNS). Despite the high level of solar activity, the HNS at high latitude still organizes solar wind stream structure much as it did near the previous solar minimum. The recurrent coronal streamers originate slow solar wind and mark the northern extremity of a very tilted HNS whose passage at Ulysses is accompanied by slow, dense solar wind, enhanced temperature, depressed α abundance, enhanced magnetic fields, and magnetic field directional changes that evolve with spacecraft latitude.     

A morphological, sedimentological and geophysical investigation of the Woore Moraine, Shropshire, England

The Bar Hill-Whitchurch-Wrexham Morainic Complex is a large-scale glacial landform thought to represent either the maximum extent or the re-advance of the British-Irish Ice Sheet during the Late Devensian. The origin of the moraine remains uncertain as its key characteristics have not been studied in detail due to a lack of exposures from which its large-scale structure can be determined. The development of new technologies has enabled detailed examination of the topography and internal structure of such large-scale landforms. This paper describes a multi-disciplinary approach involving digital geomorphological mapping using enhanced resolution NextMAP™ digital surface models, geophysical imaging (electrical resistivity tomography) and conventional sedimentological analyses. This combination of techniques is useful for elucidating the origin of a large glacial landform in a region of poor exposure. Digital elevation models such as NextMAP™ offer an efficient and accurate method for landform-mapping, whilst electrical resistivity tomography was able to map the major constituent sediments of the moraine, which had in turn been identified in the single exposure available. Additional geophysical techniques should however be applied to provide further structural data and thereby enable a more detailed interpretation of the moraine's internal structure. Preliminary findings indicate that the moraine is a glaciotectonic landform composed of diamicton and glaciofluvial sediments, an origin consistent with recent suggestions that the Cheshire Plain contained an active ice lobe during the last glacial maximum.     

太阳爆发过程中的大尺度磁重联电流片:理论和观测

从理论和观测两个方面来介绍和讨论出现在太阳爆发过程中的磁重联电流片及其物理本质和动力学特征。首先介绍在理论研究和理论模型中,磁重联电流片是如何在爆发磁结构当中形成并发展的,对观测研究有什么指导意义。然后介绍观测工作是从哪几个方面对理论模型预测的电流片进行证认和研究的。第三,将介绍观测研究给出了哪些过去所没有能够预期的结果,这些结果对深入研究耀斑一CME电流片以及其中的磁重联过程的理论工作有什么重要的、挑战性的意义。第四,讨论最新的与此有关的理论研究和数值实验。最后,对未来的研究方向和重要课题进行综述和展望。     

基于CryoSat-2雷达高度计数据的南极内陆冰盖高程变化与物质平衡

南极冰盖对海平面影响巨大,高程变化测量是南极物质平衡监测的重要手段。采用欧空局CryoSat-2雷达高度计数据,通过提取卫星升降轨的地面交叉点,监测了南极内陆冰盖的高程变化（物质平衡）。结果表明,后向散射能量对Ku波段的CryoSat-2雷达高度计的高程数据具有一定的影响,经后向散射能量校正后,时间序列上的高程变化变得平缓,高程变化与已有的降雪数据相比,更加符合实际情况。2010年11月至2017年11月南极内陆冰盖高程变化趋势为（-1.1±0.2）cm·a^-1。西南极的Kamb冰流高程变化率为（38.7±1.1）cm·a^-1,Moeller冰流高程变化率为（-10.3±1.2）cm·a^-1,部分Thwaites冰川区域高程变化率为（-13.4±1.8）cm·a^-1,东南极的Wilkes Land出现高下降区,最高达-20 cm·a^-1。Dronning Maud Land虽然出现变化异常的点,但整体并没有显著的高程变化。南极内陆冰盖质量变化为（-10.6±6.2）Gt·a^-1,整体上南极内陆冰盖质量变化平缓,部分区域变化较大,Kamb冰流达到（17.9±0.5）Gt·a^-1,Moeller冰流达到（-3.4±0.4）Gt·a^-1,部分Thwaites冰川区达到（-3.7±0.5）Gt·a^-1。     

脱气温度和样品粒径对致密砂岩低温氮气吸附实验结果的影响

基于静态体积法的低温氮气吸附实验已广泛用于分析致密储集层的孔隙结构。本文探索了脱气温度和样品粒径对松辽盆地高台子致密砂岩低温氮气吸附实验结果的影响。结果显示,110℃的脱气条件并不能清除束缚水而使得孔隙体积、比表面积均偏低,300℃的脱气条件容易破坏样品中黏土矿物的结构令孔隙体积、比表面积减小,200℃是比较合适的脱气温度,既能去除束缚水又不破坏黏土矿物结构。样品粒径从5～10目减小至10～30目,氮气探测的孔隙数量增多使比表面积、孔体积增大。从10～30目减小至180～200目,黏土矿物相对含量降低令比表面积、孔体积显著减小;小于200目的样品中减少的黏土矿物主要集中在大于200目的岩样中,因此大于200目岩样的测定结果最高。因此,10～30目是利用低温氮气吸附实验寻求分析致密砂岩储集层特征的最佳粒径范围。     

Meltwater discharge during the Holocene from the Wilkes subglacial basin revealed by beryllium isotope analysis of marine sediments

Understanding Antarctic Ice Sheet dynamics related to global climate change is of scientific and societal interest as the future behaviour of the ice sheet under the currently changing climate is unknown. We present beryllium‐10 (¹⁰Be) analysis of a high‐resolution marine sediment core from the Adélie Basin near the eastern Wilkes Land margin, which is susceptible to marine ice sheet instability due to the low‐lying nature and down‐sloping trough of the Wilkes Subglacial Basin. Combined with a newly constructed age model using compound specific radiocarbon dates, the data reveal three events associated with high meteoric ¹⁰Be at ca. ~10 ka, ca. ~6.5 ka and from ca. ~4 ka. We interpret these high meteoric ¹⁰Be events to be derived from the deposition of ¹⁰Be released from the ice sheet during meltwater discharge. In particular, the shift to higher meteoric ¹⁰Be concentration at~4 ka may correspond to changes in climate patterns at this time. Copyright © 2019 John Wiley & Sons, Ltd.     

Android平台下的地形图图幅信息检索

针对当前移动端缺少快速、实时检索地形图图幅信息的系统,本文依据国家基本比例尺地形图分幅与编号标准,提出了基于Andriod平台的地形图图幅信息检索方法并编程实现了该系统。该系统实现的功能有:点所在图幅编号检索、图幅范围检索、地形图新旧编号的转换及区域范围内图幅编号集检索。此系统可应用于Andriod智能手机和平板电脑等移动设备。实验表明,本文的方法和系统执行效率能够基本满足移动用户实时检索地形图图幅信息的需求。     

平面冰层覆盖下水中声传播损失特性分析

理论计算了冰层的声波反射系数,分析了平面冰层覆盖下水中声传播损失特性。将冰层视作平面覆盖层,建立了"空气-冰层-水"结构的冰层反射物理模型,结合冰中的物理声学参数,得到冰层反射系数;利用Bellhop海洋声学传播模型得到冰层覆盖下声场的传播损失,对比分析了传播损失与声波频率、声源深度的关系;结合冰层反射系数计算结果,解释了冰下信道具有频率选择性的原因。结果表明,冰层覆盖下声场传播具有明显的频率选择性,这种频率选择性是由声波频率和冰层厚度共同决定的。