Long-term pan evaporation observations as a resource to understand the water cycle trend: case studies from Australia

Abstract

Acceleration of the global water cycle over recent decades remains uncertain because of the high inter-annual variability of its components. Observations of pan evaporation (E_pan), a proxy of potential evapotranspiration (ET_p), may help to identify trends in the water cycle over long periods. The complementary relationship (CR) states that ET_p and actual evapotranspiration (ET_a) depend on each other in a complementary manner, through land–atmosphere feedbacks in water-limited environments. Using a long-term series of E_pan observations in Australia, we estimated monthly ET_a by the CR and compared our estimates with ET_a measured at eddy covariance Fluxnet stations. The results confirm that our approach, entirely data-driven, can reliably estimate ET_a only in water-limited conditions. Furthermore, our analysis indicated that ET_a did not show any significant trend in the last 30 years, while short-term analysis may indicate a rapid climate change that is not perceived in a long-term perspective.

Editor Z.W. Kundzewicz; Associate editor D. Gerten

Citation Lugato, E., Alberti, G., Gioli. B., Kaplan, J.O., Peressotti, A., and Miglietta, F., 2013. Long-term pan evaporation observations as a resource to understand the water cycle trend: case studies from Australia. Hydrological Sciences Journal, 58 (6), 1287–1296.     

一种基于WiFi Direct技术的位置信息共享方法

当移动设备处于离线状态时,设备之间难以实现基于位置的信息共享。本文尝试利用Android设备搭载的WiFi Direct技术建立无线自组织网络的方法,实现了在该网络下位置信息的共享,并对该网络的性能进行了测试,同时考虑了设备中存在有设备与服务器连接时的信息共享情况。试验表明,该方法可在一定程度上解决因网络中断,设备之间不能进行位置等信息的共享或从服务器获取信息的问题。     

信息与通信技术对空间组织的影响及其空间效率的测算

为了更好地展示工业时代的空间组织模式,给出了一个包括时空背景、组织主体、组织客体、要素组成、要素状态、空间效率和技术7个部分的概念性框架;以该框架为基础,逐步分析了信息与通信技术对空间组织其他6个部分的具体作用;最后提出了一个判定空间组织效率的新视角。研究发现,信息与通信技术导致了传统空间组织模式的根本性重构,其对空间组织的影响是全方位的;在过去的30多年间,信息与通信技术对劳动生产率增长的贡献显著,这也证明了其作用下空间组织的高效率。     

Identification of buried sinkholes using refraction tomography at Ft. Campbell Army Airfield,Kentucky

Karst aquifers are highly susceptible to contamination, with numerous points of entry for contaminants through recharge features such as sinkholes, swallow holes and solutionally enlarged fractures. These recharge features may be filled or obscured at the surface, requiring the use of geophysical or remote sensing techniques for their identification. This study uses seismic refraction data collected at the Ft. Campbell Army Airfield (CAAF), Kentucky, USA, to test the hypothesis that refraction tomography is a useful tool for imaging bedrock depressions beneath thick overburden (greater than 20 m of unconsolidated sediment). Southeast of the main taxiway of CAAF seismic velocity tomograms imaged a bedrock low, possibly a closed depression, at a depth of 25 m that had been earlier identified through delay-time analysis of the same refraction data. Tomography suggests the bedrock low is about 250-m wide by 10-m deep at its widest point. High rates of contaminant vapor extraction over the western extension of this feature suggest a high concentration of contaminants above, and within, this filled bedrock low, the base of which may contain solutionally enlarged fractures (i.e. karst conduits) that could funnel these contaminants to the upper or lower bedrock aquifers. This study thus demonstrates the viability of seismic refraction tomography as a tool for identification of filled sinkholes and bedrock depressions in karst areas.     

浅析地质勘查单位网站建设

阐述了如何建设地勘单位网站,并对网站做了整体规划,在网站的功能设计与结构设计及其具体技术实现上进行了细致的描述。     

1975-2006年西藏羊卓雍错流域内湖泊水位变化对气候变化的响应

根据1975年地形图、1988年至2006年的TM、CBERS卫星遥感资料和1962-2006年逐年平均气温、降水量、蒸发量、相对湿度、风速和日照时数等气象资料以及1974-2005年的湖泊水位水文资料,对西藏羊卓雍错及其流域内的空姆错、沉错和巴纠错等4个湖泊的水位变化以及对气候变化的响应作了分析.结果表明:该区湖泊面积在近30 a来呈缓慢下降趋势,2005年与1975年相比,分别减少了46.55 km2、1.73km2、0.03 km2、6.01 km2,减少幅度分别为7.2%、4.3%、0.1%、13.6%.其主要原因是,由于羊卓雍错的湖水主要以降水补给为主,在降水增加、气温上升的情况下由于升温引起的湖泊蒸发效应超过降水增加导致的补给影响,是湖泊面积下降的主要原因.     

塔里木盆地北部油气运移二维二相数值模拟分析

油气运移和聚集过程实际上是油（气）水饱和度知疏导层的变化过程，盆地中油（气）二相流动问题的研究就是对这一过程的定量描述，本项研究是在前人工作基础上，考察压实作用造成骨架变形来推导新的二维二相流动方程，它容描述异常压力演化与二相流动于一式，在模拟方法上采用有限分析的数值方法，这应用于新疆塔里木盆地北部地区，展示了该区异常压力、含水饱和度弥散状扩散效应以及流速场在地质历史时期动态模拟演化特征；指出了该     

深海沉积物分类与命名的参数指标和主成分分析

对于南海中部(118个表层沉积物样,水深82~4 420 m)、东部(106个表层沉积物样,水深700~4 508 m)海域的表层沉积物的粒度资料按小于200 m,200~2 000 m,大于2 000 m水深段对水深、平均粒径、黏土含量进行统计分析,结果表明从陆架到陆坡再到深海,平均粒径和黏土含量随水深增加呈非常有规律的变化;把大于2 000 m水深区域再细分为大于2 500 m,大于3 000 m,大于3 500 m,结果表明平均粒径和黏土含量随水深增加几乎无变化,在南海中部水深大于2 000 m海域平均粒径为3.39~3.54μm,黏土平均含量为54.91%~55.47%;在南海东部水深大于2 000 m海域平均粒径为3.25~3.37μm,黏土平均含量为53.91%~54.56%。研究表明2 000 m水深具有划分深海沉积物的指示意义。南海中部水深大于2 000 m海域黏土平均含量为55.19%,平均粒径为3.39μm;在南海东部水深大于2 000 m海域黏土平均含量为53.91%,平均粒径为3.37μm;在南海中部、东部水深大于2 000 m海域平均粒径均小于4μm,黏土平均含量均大于50%,表明深海沉积物粒度特征是平均粒径小于4μm和黏土平均含量大于50%。黏土含量是非生物组分的代表和划分深海沉积物类型的一个独立参数,钙质生物和硅质生物组分是另外两个独立参数。南海东部海域表层沉积物中55种元素总含量为47.50%,硅、铝、钛、钠、钾、磷、钙、镁、铁、锰十种主元素含量为47.03%,其他45种元素含量为0.47%,虽然沉积物来源复杂、成因不同,但沉积物化学主成分并不复杂,主要由前10种主元素和氧元素组成。沉积物主元素铝、钙、硅分别富集于黏土、钙质沉积、硅质沉积中。通过建立沉积物生源组分与碳酸钙、三氧化二铝、二氧化硅的量化关系,可把碳酸钙、生物二氧化硅作为钙质生物和硅质生物的两个替代参数。     

THE RELATIVE CONTRIBUTION OF SOIL TILLAGE AND OVERLAND FLOW EROSION TO SOIL REDISTRIBUTION ON AGRICULTURAL LAND

This study uses evidence for the long-term (35 years) pattern of soil redistribution within two agricultural fields in the UK to identify the relative importance of tillage and overland flow erosion. Spatially distributed long-term total soil redistribution data for the fields (Dalicott Farm and Rufford Forest Farm) were obtained using the caesium-137 (¹³⁷Cs) technique. These data were compared with predicted patterns of soil redistribution. Recent studies have demonstrated that the redistribution of soil by tillage may be described as a diffusive process. A two-component model was, therefore, developed which accounts for soil redistribution by both overland flow and diffusive processes. Comparison of the predicted patterns of overland flow erosion alone with the observed (¹³⁷Cs-derived) data indicated a poor agreement (r² = 0.17 and 0.11). In contrast, a good agreement exists between the predicted pattern of diffusive redistribution and the observed data (r² = 0.43 and 0.41). These results give a clear indication that diffusive processes are dominant in soil redistribution within these fields. Possible diffusive processes include splash erosion, soil creep and tillage. However, the magnitude of the diffusion coefficients for the optimum predicted pattern (c. 350–400 kg m⁻¹ a⁻¹) demonstrates that tillage is the only process capable of explaining the very significant soil redistribution which is indicated by the ¹³⁷Cs data. Consideration is given to the implications of these results for both soil erosion prediction and landscape interpretation.     

A hybrid approach to modeling territorial control in violent armed conflicts

Territorial control is central to the understanding of violent armed conflicts, yet reliable and valid measures of this concept do not exist. We argue that geospatial analysis provides an important perspective to measure the concept. In particular, measuring territorial control can be seen as an application of calculating service areas around points of control. The modeling challenge is acute for areas with limited road infrastructure, where no complete network is available to perform the analysis, and movements largely occur off road. We present a new geospatial approach that applies network analysis on a hybrid transportation network with both actual road data and hexagon‐fishnet‐based artificial road data representing on‐road and off‐road movements, respectively. Movement speed or restriction can be readily adjusted using various input data. Simulating off‐road movement with hexagon‐fishnet‐based artificial road data has a number of advantages including scalability to small or large study areas and flexibility to allow all‐directional travel. We apply this method to measuring territorial control of armed groups in Sub‐Saharan Africa where inferior transport infrastructure is the norm. Based on the Uppsala Conflict Data Program's (UCDP) Georeferenced Event Data (GED) as well as spatial data on terrain, population locations, and limited transportation networks, we enhance the delineation of the specific areas directly controlled by each warring party during civil wars within a given travel time.