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利用长江上游最近30年(66个测站)蒸发皿蒸发量和最近50年(90个测站)的7种气象要素,分析了蒸发皿蒸发量的区域变化趋势和影响蒸发皿蒸发量变化的因素;针对7个水文站的年径流量变化,探讨了蒸发皿蒸发量变化后对水分循环的影响.结果表明,长江上游蒸发皿蒸发量的变化可以划分为三个分区,研究区域东西两侧(青藏高原和大巴山一带)为显著减少区,分别命名为RⅠ和RⅡ,中间(云贵高原北部到黄土高原南缘以及由二者包围的四川盆地一带)为显著增大区,命名为RⅢ区.影响区域蒸发皿蒸发量变化的原因各有不同,青藏高原一带(RⅠ区)蒸发皿蒸发量减少的原因可归结于太阳辐射强度和风动力扰动减弱所致.大巴山一带(RⅡ区)减少原因是太阳辐射强度、风动力扰动强度、湿度条件都在显著下降所引起的.云贵高原到四川盆地一带(RⅢ区)蒸发皿蒸发量增加是环境气温强烈升高,导致其上空大气水汽含量显著减少,大气很干燥,引发蒸发过程加强所致.蒸发皿蒸发量发生变化的直接后果就是导致水分循环强弱发生变化,对于RⅠ区,尽管蒸发皿蒸发量减少,由于降水量和径流量增加的作用,这一区域的水分循环有所加强.在RⅡ区,降水量、径流量和蒸发量都在减少,因此RⅡ区水分循环显著减弱.在RⅢ区,降水量和径流量同时减少,而蒸发量增大,水量消耗增大,因此RⅢ区水分循环有减弱趋势. 相似文献
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为了研究风场对背风波的影响,针对边界层附近为弱稳定层结的背风波,建立了一个三维三层的理论模型和线性计算模式,分析了各层中风速和风向的变化对背风波特征的影响,揭示了气流过孤立山脉产生背风波的有利风场条件。结果表明:背风波的波长、振幅等特征对各层风速和风向的变化具有相当的敏感性,波长随着低、高层风速的增大而增大,随着中层风速的增大先减小后增大;振幅随着低、中层风速的增大先增大后减小,随着高层风速的增大而增大。此外,风速和上下层风向切变的增大均使背风波的形态逐渐由横波型转为辐散型,但是上下层风向的切变对背风波形态的影响比风速更为显著。 相似文献
96.
Wenwu Tang Wenpeng Feng Meijuan Jia 《International journal of geographical information science》2013,27(3):412-439
This study presents a massively parallel spatial computing approach that uses general-purpose graphics processing units (GPUs) to accelerate Ripley’s K function for univariate spatial point pattern analysis. Ripley’s K function is a representative spatial point pattern analysis approach that allows for quantitatively evaluating the spatial dispersion characteristics of point patterns. However, considerable computation is often required when analyzing large spatial data using Ripley’s K function. In this study, we developed a massively parallel approach of Ripley’s K function for accelerating spatial point pattern analysis. GPUs serve as a massively parallel platform that is built on many-core architecture for speeding up Ripley’s K function. Variable-grained domain decomposition and thread-level synchronization based on shared memory are parallel strategies designed to exploit concurrency in the spatial algorithm of Ripley’s K function for efficient parallelization. Experimental results demonstrate that substantial acceleration is obtained for Ripley’s K function parallelized within GPU environments. 相似文献
97.
利用SOHO/SEM在1996-2008年的太阳EUV观测数据,比较和评估F10.7和Mg II作为EUV代理参数的代表性,不能支持Viereck等关于Mg II是比F10.7更好的代理参数的结论.通过比较对两种参数的多种回归计算结果,确立双因子极大似然估计方法构建EUV计算模式,通过模型计算结果与SEM观测数据比较,表明该模型能够很好地重建EUV数据系列.利用该模式,构建了1978年11月以来的太阳极紫外辐射数据序列. 相似文献
98.
《International Journal of Digital Earth》2013,6(10):789-810
One of the problems in virtual globes technologies is the real-time representation of vegetal species. In forest or garden representations, the low detailed plants produce a lack of realism. Efficient techniques are required to achieve accurate interactive visualisation due to the great number of polygons the vegetal species have. This article presents a multi-resolution model based on a geometric representation of vegetal species that allows the application to perform the progressive transmission of the model, that is, the transmission of a simple representation followed by successive refinements of it. It has a hardware-oriented design in order to obtain interactive frame rates. The geometric data of the objects are stored in the graphics processing unit and, moreover, the change from one approximation to another is obtained by performing mathematical calculations in this graphics hardware. The multi-resolution model presented here enables instancing: as many vegetal species as desired can be rendered with different levels of detail, while all of them are accessing the same geometric data. This model has been used to build a real-time representation of a not imaginary scenario. 相似文献
99.
Most of pan-sharpening techniques require the re-sampling of the multi-spectral (MS) image for matching the size of the panchromatic (Pan) image, before the geometric details of Pan are injected into the MS image. This operation is usually performed in a separable fashion by means of symmetric digital low-pass filtering kernels with odd lengths that utilize piecewise local polynomials, typically implementing linear or cubic interpolation functions. Conversely, constant, i.e. nearest-neighbour, and quadratic kernels, implementing zero and two degree polynomials, respectively, introduce shifts in the magnified images, that are sub-pixel in the case of interpolation by an even factor, as it is the most usual case. However, in standard satellite systems, the point spread functions (PSF) of the MS and Pan instruments are centered in the middle of each pixel. Hence, commercial MS and Pan data products, whose scale ratio is an even number, are relatively shifted by an odd number of half pixels. Filters of even lengths may be exploited to compensate the half-pixel shifts between the MS and Pan sampling grids. In this paper, it is shown that separable polynomial interpolations of odd degrees are feasible with linear-phase kernels of even lengths. The major benefit is that bi-cubic interpolation, which is known to represent the best trade-off between performances and computational complexity, can be applied to commercial MS + Pan datasets, without the need of performing a further half-pixel registration after interpolation, to align the expanded MS with the Pan image. 相似文献
100.
Takashi Morita 《制图学和地理信息科学》2013,40(2):140-151
ABSTRACTBertin’s first book, Semiology of Graphics, was published in 1967. His second book, Graphics and Graphic Information Processing, was subsequently published in 1977. The word “processing” in the title of the second book is interesting because in those days there were no personal computers with an interactive display system. But in Bertin’s laboratory there were many kinds of tool kits – basically manually developed thematic maps and data analysis. Bertin’s methods were concerned with making a thematic map and data visualization. Maps, and more generally graphics, were represented by sets of cartographic symbols. Thus, they are abstractions that demand both theoretical and technical literacy to represent and understand them. If the representation is systematic, a sort of tool kit might be necessary, because the representation demands consistency based on the theory. Otherwise a cartographer faces the risk of an unstable and unintelligible representation. In this paper, we discuss the discrimination between tool kits intended either for an automated system or a process assisting system. The latter process might be useful and necessary to develop a graphic way of thinking. This investigation refers to Bertin’s books, materials conserved at the National Archives in Paris, and other related software developed later.Abbreviation: EHESS: Ecole des Hautes Etudes en Sciences Sociales inherited Ecole Pratique des Hautes Etudes since 1975 相似文献