A comparison of ASCE and FAO-56 reference evapotranspiration for a 15-min time step in humid climate conditions     

Ayman A. Suleiman  Gerrit Hoogenboom   《Journal of Hydrology》2009,375(3-4):326-333

Many applications in diverse disciplines require estimates of evapotranspiration (ET) at hourly or smaller time steps. The primary objectives of this study were to compare the American Society of Civil Engineers (ASCE) and FAO-56 Penman–Monteith equations for 15-min ET₀ (ET_{0,15-min,ASCE} and ET_0,15-min,FAO) estimations for humid climate conditions and to compare the 24 h sum of ASCE (ET_0,24 h,ASCE) and FAO-56 15-min ET₀ (ET_0,24 h,FAO) with the daily ET₀ (ET_0,d,FAO) computed from the daily FAO-56 equation, which is identical to ASCE daily ET₀ equation. Ten-year, i.e., 1997–2006 continuous 15-min and daily weather data for 11 representative and well-distributed sites throughout Georgia, USA were used. It was evident that during the day, ET_{0,15-min,ASCE} was higher than ET_0,15-min,FAO due to a lower surface resistance parameter value, while at night ET_{0,15-min,ASCE} was lower than ET_0,15-min,FAO due to a higher surface resistance parameter value. The ET_0,15-min,FAO was about 5% less than ET_{0,15-min,ASCE} and ET_0,24 h,FAO was about 5% lower than ET_0,24 h,ASCE. The difference between ET_{0,15-min,ASCE} and ET_0,15-min,FAO during the day and night was highly dependent on wind speed. During the three summer months, i.e., June, July and August, on average, ET_0,24 h,FAO was only 1% higher than ET_0,d,FAO while ET_0,24 h,ASCE was 5% higher than ET_0,d,FAO. For the entire year, ET_0,24 h,FAO was 8% higher than ET_0,d,FAO while ET_0,24 h,ASCE was 13% higher than ET_0,d,FAO. The ET_0,24 h,FAO and ET_0,d,FAO had a better agreement than ET_0,24 h,ASCE and ET_0,d,FAO throughout the year and during the summer months. It is also worth noting that the daily calculations for FAO-56 and ASCE were identical. These results demonstrated that for applications that require 15-min time steps or daily ET₀ for the entire year, the use of ET_0,15-min,FAO and ET_0,24 h,FAO, respectively, will yield more consistent outcomes. The use of ET_0,d,FAO during the summer months can be as accurate as the use of ET_0,24 h,FAO for applications that require daily time steps, such as irrigation scheduling.  相似文献   

带晕线的居民地符号的自动识别     

叶建栲  任留成  赵琪 《测绘学院学报》1999,(2)

针对１∶５ 万地形图中带晕线的居民地符号的特点, 提出了一种基于图像退缩和膨胀算法的居民地符号自动识别方法。  相似文献   

National Center for Geographic Information and Analysis     

Nicholas M. Short Jr  Leonard Dickens 《International journal of geographical information science》2013,27(1):47-52

Abstract

Abstract. The growth of the remote sensing field has caused and explosion in the size and complexity of Earth satellite image databases. The explosion of data is already challenging current satellite-based GIS databases. New technologies for information management will be required in the future to maintain these large geographically-oriented systems created by projects such as NASA's Earth Observing System (EOS). This paper presents a technology adapted from the planning/scheduling field in Artificial Intelligence (AI) that promises to automate and facilitate the process of creating and storing satellite images and their associated data products.  相似文献   

Using Contents Addressable Filestore for rapid access to a large cartographic data set†     

STEPHEN WISE 《International journal of geographical information science》2013,27(2):111-120

Abstract

The need for rapid access to large amounts of data is one of the central problems in the field of geographical information systems. This paper describes the use of a hardware solution to this problem, in the particular case of selecting digitized boundary data from a very large file. The hardware is International Computers'(ICL's) award winning Contents Addressable Filestore (CAFS) which is a special unit fitted to ICL disc drives allowing the fast selection of records from large files. By reformatting the boundary data, it was possible to perform searches using CAFS. A command-driven package was written to allow users to select the boundaries for any named zone or zones, display them on a graphics terminal and write them out in a format suitable for input to the GIMMS package. This package was tested on a file containing the boundaries of all the wards of Great Britain. After reformatting, this file was 6 Mbytes in size, but by means of CAFS could be searched interactively with response times of the order of 5-10 seconds.  相似文献   

Low temperature alteration of magmatic Ni-Cu-PGE sulfides as a source for hydrothermal Ni and PGE ores: A quantitative approach using automated mineralogy     

《Ore Geology Reviews》2017

Magmatic Ni-Cu-PGE sulfide assemblages are almost ubiquitously comprised of pyrrhotite-pentlandite-chalcopyrite(-pyrite). Sulfide alteration is common during syn- or post-magmatic fluid interaction, usually replacing sulfides with amphiboles or serpentine. However, some are altered to a low temperature (<200 °C) hydrothermal assemblage of pyrite-millerite-chalcopyrite (PMC). An example is the Ni-Cu-PGE mineralisation in the Grasvally-Norite-Pyroxenite-Anorthosite (GNPA) Member, northern Bushveld Complex, which displays a continuum of mineralogical styles formed through progressive alteration: Style 1 primary pyrrhotite-pentlandite-chalcopyrite; which is altered to Style 2 pyrrhotite-pyrite-pentlandite-chalcopyrite; Style 3 pyrite-pentlandite-chalcopyrite; Style 4 pyrite-pentlandite-millerite-chalcopyrite; and Style 5 pyrite-millerite-chalcopyrite-cubanite. Modelling using CHILLER confirms this mineralogical sequence is thermodynamically possible at ∼200 °C. Quantitative characterisation using automated Energy-Dispersive X-ray spectroscopy mapping alongside in situ laser ablation analyses determined mineral proportions, major and trace element concentrations and deportments in each style. The early loss of pyrrhotite removes over half of the bulk Fe and S during the initial stages of PMC alteration, increasing Cu, Ni and PGE tenors of the remaining sulfides significantly. As water–rock interaction progresses, pyrrhotite is replaced by pyrite and pentlandite by millerite, with concurrent losses in Fe, S and Ni. Copper is lost throughout the alteration, and is most pronounced in the more advanced stages. The fluids responsible were most likely acidic and oxidised, with metals mobilised as chloride complexes. Using Rh as an immobile normalising element, the overall mass loss in the most altered samples is calculated to be up to 90%, consistent with textural relationships that indicate 40–90% volume loss from Styles 2–5, with sulfides replaced by secondary silicates, including phlogopite, quartz, chlorite, pyroxenes and minor amphiboles. Magnetite is not a significant alteration product and thus Fe is mobilised, or incorporated into silicates. Most trace elements present in the magmatic sulfide (the IPGE, Rh and Bi) remain in the sulfide phases, and are effectively transferred to pyrite during PMC alteration, except Pd, which remains in pentlandite, and is liberated from the sulfide assemblage when pentlandite disappears. Selenium tenors increase slightly with alteration, demonstrating that alteration decreases S/Se ratios. The significant mobilisation of Ni, Cu and Pd during PMC alteration produces fluids enriched in these elements that may represent a metal source for a number of enigmatic hydrothermal Ni deposits such as Avebury, Enterprise and Talvivaara, whose metal sources remain speculative. The PMC alteration of the GNPA Member may be specifically a source for the nearby Waterberg hydrothermal Pt deposit. Furthermore, this study has implications not only for magmatic ore deposits, but also for the general implications of sulfide transformation and metal transfer in ore systems in general.  相似文献   

基于DEM的流域特征提取综述   总被引：44，自引：0，他引：44  

李丽  郝振纯 《地球科学进展》2003,18(2):251-256

回顾了自DEM出现以来它在流域特征提取方面的应用和发展,论述和比较了提取流域特征的各种方法。包括确定流向的单流向法（D8法、Rho8法、Lea方法、DEMON法以及 D∞法）和多流向法;提取河网的识别谷点法和基于流向提取河网的方法;提取河网过程中洼地和平原区的流向确定、河网提取的方法;划分子流域和提取流域边界线的方法;计算分布式子流域特征的方法,其中重点论述了子流域长度和坡度的计算方法,以及提取控制点所控制的排水区的方法。  相似文献   

示意性地图自动设计初探     

董卫华  郭庆胜  刘纪平 《测绘科学》2007,32(Z1):37-39

分析并总结示意性地图的理论基础和基本设计原则。在几种基于矢量制图信息的典型示意性地图设计方法的基础上,提出基于几何、语义多约束条件下的示意性地图的设计方案。采用迭代优化算法,自动生成满足几何、语义和审美要求的示意性地图。  相似文献   

数字式海图制图在中国的进展     

赵玉柱 《测绘学院学报》1991,(4)

本文以殷实先进的研究成果和独自开发的软件系统为科学基础,探讨了采用现代电子计算机技术进行数字式海图制图的基本原理、技术方法和解决某些技术难点的途径,并在一定深度上探讨了数字式测量资料的应用、汉字自动注记和海图数据库的建立模式等技术问题。  相似文献   

微机绘制露天矿采剥工程平面图     

汪家琪  曾昭红 《测绘工程》1996,5(4):51-55

露天矿生产过程中，需要及时提供采剥工程平面图。文中介绍了微机自动绘制露天矿采剥工程平面图的原理和方法，着重阐述了验收边界数据的接合处理方法及注记重叠的自动处理方法。  相似文献   

联合Envisat和ALOS卫星影像确定 L'Aquila地震震源机制     

温扬茂  何平  许才军  刘洋 《地球物理学报》2012,55(1):53-65

2009年4月6日意大利L'Aquila地区发生了M_w6.3级地震,该地震造成了300余人的人员死亡. 本文联合不同波长、不同入射倾角的升降轨Envisat和ALOS卫星的差分干涉数据对该地震进行震源机制解的反演研究. 研究首先对卫星雷达影像进行二通差分干涉处理,获取了覆盖L'Aquila地震震区的完整InSAR同震形变场,然后结合四叉树和均匀采样方法对原始观测数据进行降采样. 在此基础上,联合GPS形变观测数据,利用弹性半空间矩形和三角位错模型,以及断层自动剖分技术对断层面进行最优离散剖分,反演获取了发震断层的精确几何参数和最优断层滑动分布,结果显示分布式三角位错滑动模型能够很好地解释观测到的地表形变场. 反演结果表明发震断层是一个以正倾滑为主兼有少量右旋走滑的盲断层;基于观测数据最优确定的断层单元的最短边长为0.4 km,最长边长为6.3 km;此次地震的滑动分布主要发生在5～14 km深度的范围内,最大滑移量为1.07 m,释放的能量为3.43×10¹⁸ N·m(M_w6.32),与地震学的研究结果非常一致.  相似文献