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101.
大型GIS与数字地球的空间数学基础研究 总被引:14,自引:3,他引:14
将地图投影概念由传统的曲面到平面的变换扩展为曲面到曲面的变换,并提出一套适合于大型GIS和地球数字产品的实用“地图投影”模型。该模型的视图采用等距离切圆柱投影,度量空间是椭球面几何系统,符合计算机环境下GIS视图与度量空间分离的特性。鉴于全球多分辨率连续可视化,精密可视化量算,三维、多维地球数据统一,标准的空间定位框架和只有在统一的空间系统内,全球资源、生态环境数据才能进行精确的地理分析等4个方面的需要,从地图投影发展到本模型将是方向和技术趋势。 相似文献
102.
A New Coastal Marine Ecosystem Model Study Coupled with Hydrodynamics and Tidal Flat Ecosystem Effect 总被引:3,自引:0,他引:3
Akio Sohma Yasuyuki Sekiguchi Hiroshi Yamada Tatsuaki Sato Kisaburo Nakata 《Marine pollution bulletin》2001,43(7-12):187-208
A new coastal marine ecosystem model was developed, which was composed of pelagic and benthic ecosystems, and was applied to Mikawa Bay, Japan. This model deals with variations of biochemical and physical interactions among dissolved oxygen and C–N–P species (composition formed out of carbon, nitrogen and phosphorus elements) so that it resolves the flux dynamics of carbon, nitrogen, phosphorus and oxygen elements. The physical and biochemical mechanism figured in this model is constructed for the purpose of simulating the estuarine lower trophic ecosystem, in areas where the sea was too deep for light to reach the sea-bottom. As a result of coupling the benthic with pelagic system, the effect of process of sedimentation and nutrient diffusion back to the pelagic system could be indicated. In addition, by implementing the tidal flat ecosystem model's calculation result, the integrated model can include the effect of water purification in tidal flats where the light can reach the sea-bottom, and where sea-weed, sea grass and benthic algae exist. In this study, the model indicates that oxygen-depleted water exists at the sea-bottom especially in summer mainly caused by an increase of oxygen consumption in the benthic system and a decrease of the vertical mixing water process. Furthermore, by comparing the case – with the tidal flat ecosystem model and the case without it, the effect of water purification of tidal flat estuaries was indicated. From the viewpoint of a short time scale, the tidal flat has the potential to restrict red tide (rapid increase of phytoplankton), and from the viewpoint of a long time scale, it restricts the sedimentation of detritus. Restricting the sedimentation prevents oxygen-depleted water occurring in the coastal marine system of Mikawa Bay. 相似文献
103.
Pollani Annika Triantafyllou George Petihakis George Nittis Konstantinos Dounas Costas Christoforos Koutitas 《Marine pollution bulletin》2001,43(7-12):270-278
In this work the development and the application of an operational management tool for the Greek Seas is described. This tool consists of a three-dimensional floating pollutant prediction model coupled with a weather, a hydrodynamic and a wave model in order to track the movements and the spreading of the pollutants and indicate those coastal areas which might be affected. The tool is part of the Poseidon system which has been designed to provide real time data and forecasts for marine environmental conditions in the Greek Seas. In this paper, we present four case studies based on realistic scenarios that show the value of the application for long-term strategic planning and short-term decision making in oil spill accidents. 相似文献
104.
南水北调西线雅砻江调水工程温波引水枢纽坝址径流计算的研究 总被引:1,自引:2,他引:1
南水北调西线雅砻江调水工程(简称西线调水)是从长江的一级支流雅砻江上游区引水至黄河源头地区的跨流域调水工程,是补充黄河水资源不足与解决我国西北和华北部分地区干旱缺水的重大战略措施,由于引水枢纽坝址缺乏实测水文资料,我们依据附近孜水文站实测资料,采用一些非确定性的数理统计模型来计算温波引水坝址的设计年径流量,并对计算成果进行了合理性分析,结果表明,上述计算成果基本反映了温波引水坝址径流变化的客观情况,从而为南水北调西线雅砻江调水工程缺乏实测水文资料地区的水文计算提供了科学依据。 相似文献
105.
106.
Robust估计的算法优化 总被引:2,自引:0,他引:2
本文分析了Robust估计收敛慢的原因,提出以最小二乘平差的残差(V)为初始信息,用L1估计的权函数所计算的权力初始权,根据迭代计算的残差的大小,及残差的变化所提供的信息,构造出加速收敛的算法,计算结果表明,较之一般的方法,迭代次数显著减少,辨识杠杆点含粗差的能力有较大提高,即搜索粗差的效率有很大提高。 相似文献
107.
强对流天气发生前期地面风场特征 总被引:5,自引:1,他引:5
根据对华东地区9次强对流天气的地面风场分析发现,强对流的发生发展与锋前暖区的中尺度辐合线有密切关系,与地面中尺度辐合线相伴的扰动辐合值为-0.8×10~(-4)·s~(-1)左右.当有移动的天气系统与其相遇时,交点附近扰动辐合值迅速增大,促使对流迅猛发展且移速加快.辐合线的形成与大尺度背景和特定地形有关.移动的中尺度辐合线与变压风有关而静正辐合线常与露点锋相伴. 相似文献
108.
The stability of a simple coupled ocean-atmosphere system similar to the one studied by Hirst with general ocean thermodynamics
is investigated in which the atmospheric heating is determined by sea surface temperature anomalies as well as the convergence
feedback (low level moisture convergence by the waves themselves). It is shown that the unstable coupled mode found by Hirst
(UH mode) is profoundly modified by the convergence feedback. The feedback increases the unstable range of the UH mode and
can increase its growth rate several folds. The maximally growing UH mode can become westward propagating for certain strength
of convergence feedback. If the convergence feedback strength exceeds a critical value, several new unstable intraseasonal
modes are also introduced. These modes are basically ‘advective’ modes. For relatively weak strengths of the convergence feedback
the growth rates of these modes are smaller than that of the UH mode. As the atmosphere approaches ‘moist neutral’ state,
the growth rates of these modes could become comparable or even larger than that of the UH mode. It is argued that these results
explain why the El Nino and Southern Oscillation (ENSO) signal is clear in the eastern Pacific but not so in the western Pacific
and they may also explain some of the differences between individual ENSO events. Our results also explain the aperiodic behaviour
of some coupled numerical models. Importance of this process in explaining the observed aperiodicity of the ENSO phenomenon
is indicated. 相似文献
109.
110.