结合被动微波和光学遥感的“超级寒潮”广东 地表温度特征及其对马铃薯生长的影响

利用被动微波可穿透云层的优势,基于GCOM-W1/AMSR2（Global Change Observation Mission-Water/ Advanced Microwave Scanning Radiometer 2）星载被动微波传感器的多通道亮度温度数据,反演了2016年1月下旬“超级寒潮”过程的广东省每日地表温度,分析了寒潮过程中广东省地表温度的时空变化特征。结果表明：在寒潮前后,广东省地表温度呈现出明显的先下降而后上升的趋势,寒潮过程带来的地表最低温度在广东北部大部分地区达到了277 K（4℃）,西南大部分地区为280~282 K（7~9℃）,其余大部分地区278~279 K（5~6℃）;降温幅度在广东南部地区达到了8~12 K（8~12℃）,北部大部分地区为5~7 K（5~7℃）。此外,利用归一化植被指数（NDVI）对植被生长的指示作用,基于HJ-1 A/B卫星的CCD传感器的多通道反射率数据,计算了近3年冬季广东省典型马铃薯种植区域马铃薯叶片的NDVI值,结果表明：马铃薯叶片的NDVI值在此次寒潮过程后出现了明显的下降,大部分地区（55.4%）马铃薯NDVI降低了0.1~0.2,部分地区（17.2%）马铃薯NDVI下降了0.2~0.3;进一步对比此次“超级寒潮”后同时段的前2年数据,发现寒潮后马铃薯叶片NDVI相对于正常年份也低了0.2,表明马铃薯叶片NDVI下降的主要原因是寒潮带来的低温,而不只是马铃薯的正常老化现象。NDVI的降低表明大部分地区马铃薯生长受到了抑制,马铃薯生长状况的这一变化也通过现场调查得到了证实。     

基于城市绿色生产性面积的生态补偿机制研究（英文）

我国城市扩张、粮食保障和能源转型形势严峻,如何挖掘城市建成环境的绿色生产潜力、探索一条通过粮食生产和太阳能利用节约土地空间并缓解生态压力的新途径？本文不同于以往生态补偿研究大多以重点生态功能区为对象或以财税补偿机制为手段,而是创新性地建立了一种城市空间内部的生态补偿机制。本文提出城市“绿色生产性面积”作为一种从城市生态学角度来衡量城市生态承载力提升潜力的方法,它基于将城市绿色资源收入换算成相同条件下它们所能节约的生态足迹面积。首先,通过类型学方法建立绿色生产补偿策略;其次,进行城市建成环境的全要素空间清查及其绿色生产潜力分析;最后,建立不同绿色生产的生态节地效益统一核算标准,并转换为绿色生产性土地面积指标。以天津市南开区学府街道为例,通过可利用的屋顶及闲置用地进行绿色生产,补充了该区12%的建筑所占用的自然土地所能提供的生态承载力。     

帕隆藏布河流纵剖面演化的最小功模式

河流地貌最小功原理表明河流纵误时面形态将向力示使流速增大的方向演化，据此推导出矩形流域全程流速的平均值（u^-）与河流纵误时面形态指数（N）的关系式：u^∝-f(N)={1/2-1/[(N 1)(N 2)]}^1/2，f(N)被称为流速函数。这一最小功模式表明河流纵剖面演化方向是N由小变大。以西藏帕隆藏布中上游流域系统、干流全程及Ⅰ级阶地为例，由最小功模式计算的全程流速均值与实测值相吻合，从而检验了上述最小功原理和数学模式。     

地籍信息系统中动态地块存储的实现

该文归纳了地籍信息系统中地块动态变化的基本类型 ,提出了存储动态变化信息的两种解决方案 ,分别称之为基于多边形的数据结构和基于弧段的数据结构 ,讨论了它们具体的实现 ,并比较其优缺点     

Generalised observations of wave characteristics on near‐horizontal shore platforms: Synthesis of six case studies from the North Island,New Zealand

Most field studies of wave processes on shore platforms in front of eroding cliffs focus on a single site, revealing aspects of wave dynamics at that location. Here, we analyse data from six platforms around northeastern New Zealand and describe the fundamental control of shore platform width, gradient and elevation on wave processes, including greater attenuation of short‐period waves at lower tidal stages and increases in longer period wave energy towards the cliff toe. These data suggest that empirical formulae developed from coral‐reef environments provide better predictions of wave height on platforms than formulae currently used in shore platform models.     

Traction image method for irregular free surface boundaries in finite difference seismic wave simulation

In this study, we propose a new numerical method, named as Traction Image method, to accurately and efficiently implement the traction-free boundary conditions in finite difference simulation in the presence of surface topography. In this algorithm, the computational domain is discretized by boundary-conforming grids, in which the irregular surface is transformed into a 'flat' surface in computational space. Thus, the artefact of staircase approximation to arbitrarily irregular surface can be avoided. Such boundary-conforming gridding is equivalent to a curvilinear coordinate system, in which the first-order partial differential velocity-stress equations are numerically updated by an optimized high-order non-staggered finite difference scheme, that is, DRP/opt MacCormack scheme. To satisfy the free surface boundary conditions, we extend the Stress Image method for planar surface to Traction Image method for arbitrarily irregular surface by antisymmetrically setting the values of normal traction on the grid points above the free surface. This Traction Image method can be efficiently implemented. To validate this new method, we perform numerical tests to several complex models by comparing our results with those computed by other independent accurate methods. Although some of the testing examples have extremely sloped topography, all tested results show an excellent agreement between our results and those from the reference solutions, confirming the validity of our method for modelling seismic waves in the heterogeneous media with arbitrary shape topography. Numerical tests also demonstrate the efficiency of this method. We find about 10 grid points per shortest wavelength is enough to maintain the global accuracy of the simulation. Although the current study is for 2-D P-SV problem, it can be easily extended to 3-D problem.     

Access to electricity for all and the role of decentralized solar power in sub-Saharan Africa

ABSTRACT

Several hundred million people in sub-Saharan Africa are at risk of being without access to electricity by 2030 despite the ongoing work aimed at achieving the United Nations’ Sustainable Development Goal 7—sustainable energy for all. Based on qualitative interviews, quantitative surveys, observation, and participation in Kenya and Senegal between 2010 and 2018, the author aims to explain why the rate of progress is slower than intended. The findings highlight three strong hindrances: lack of affordability due to extreme poverty, mismatch between the village-level outreach of grid-based electricity systems and the geography of settlements, and lack of consideration given to gender inequality. The findings also provide new insights into the ways that decentralized small-scale solar power increasingly meets some of the shortcomings of centralized grids in addressing these three issues, even in rural areas where grids are already present. The author concludes that the ways in which village communities have combined the use of solar-powered energy with grid-supplied energy indicates the importance of the former and the need to intensify efforts to improve solar power delivery models and integrate them fully in energy sector strategies.