A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effecti...A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effectively and the contours can be drawn smoothly based on boundaries pre-searching and local correction. An experimental example is given to demonstrate that the contours constructed by this method are of good quality.展开更多
Incremental LOD can be transmitted on the network as a stream, then users on the clients can easily catch the skeleton of terrain without downloading all the data from the server. Detailed information in a local part ...Incremental LOD can be transmitted on the network as a stream, then users on the clients can easily catch the skeleton of terrain without downloading all the data from the server. Detailed information in a local part can be added gradually when users zoom it in without redundant data transmission in this procedure. To do this, an incremental LOD method is put forward according to the regular arrangement of grid. This method applies arbitrary sized grid terrains and is not restricted to square ones with a side measuring 2 k + 1 samples. Maximum height errors are recorded when the LOD is preprocessed and it can be visualized with the geometrical Mipmaps to reduce the screen error.展开更多
针对格网DEM难以对黄土高原梯田地形进行有效数字表达的问题,基于面向对象思想提出了能够顾及梯田地形的Grid-TIN混合格网DEM(Grid-TIN based DEM,GT-DEM)概念及其数据模型,并阐明其主要特征及与传统DEM的关系。以陕西绥德县辛店沟小流...针对格网DEM难以对黄土高原梯田地形进行有效数字表达的问题,基于面向对象思想提出了能够顾及梯田地形的Grid-TIN混合格网DEM(Grid-TIN based DEM,GT-DEM)概念及其数据模型,并阐明其主要特征及与传统DEM的关系。以陕西绥德县辛店沟小流域水平梯田为例,利用现有1∶1万格网DEM、梯田特征点线及其外围边界线,构建出能够充分顾及梯田地形的GT-DEM。研究表明,利用现有格网DEM和梯田地形特征点线构建顾及梯田地形GT-DEM的技术可行。GT-DEM不仅可对研究区全局地形进行粗略表达,而且可对其局部梯田地形进行精细表达。该研究是对如何提高DEM的梯田地形数字表达能力的有益探索,对进一步提高DEM对淤地坝、鱼鳞坑等其他人工地形的数字表达能力具有重要借鉴意义。展开更多
【目的】解决现有地形复杂度误差评价方法主观性强、缺少误差解析式的问题。【方法】利用误差传播定律推导了局部高差、局部标准差、局部褶皱度和局部全曲率的中误差表达式,依据复合地形因子误差传递规律构建了复合地形复杂度指标(compo...【目的】解决现有地形复杂度误差评价方法主观性强、缺少误差解析式的问题。【方法】利用误差传播定律推导了局部高差、局部标准差、局部褶皱度和局部全曲率的中误差表达式,依据复合地形因子误差传递规律构建了复合地形复杂度指标(compound terrain complexity index,CTCI)提取的误差估计模型(error estimation model for CTCI,CEEM)。通过模拟数字高程模型(digital elevation model,DEM)试验验证了该模型的有效性,并采用三个不同地貌区域的实体DEM进行CEEM泛化试验。【结果】在不同噪声影响下,CEEM平均误差、均方差、残差和平均绝对百分比误差最大值分别为-2.1×10^(-3)、7.99×10^(-6)、8.4×10^(-3)和22.8%,决定系数均在0.961以上,CEEM整体误差微小;不同地貌类型的地形复杂度提取误差存在差异,试验统计结果表明误差由大到小依次为高山、中山、丘陵。【结论】CEEM能定量化描述地形复杂度的提取误差,可为不同复杂地形地貌区域提取复合地形复杂度指标提供参考。展开更多
Terrain characteristics can be accurately represented in spectrum space. Terrain spectra can quantitatively reflect the effect of topographic dynamic forcing on the atmosphere. In wavelength space, topographic spectra...Terrain characteristics can be accurately represented in spectrum space. Terrain spectra can quantitatively reflect the effect of topographic dynamic forcing on the atmosphere. In wavelength space, topographic spectral energy decreases with decreasing wavelength, in spite of several departures. This relationship is approximated by an exponential function. A power law relationship between the terrain height spectra and wavelength is fitted by the least-squares method, and the fitting slope is associated with grid-size selection for mesoscale models. The monotonicity of grid size is investigated, and it is strictly proved that grid size increases with increasing fitting exponent, indicating that the universal grid size is determined by the minimum fitting exponent. An example of landslide-prone areas in western Sichuan is given, and the universal grid spacing of 4.1 km is shown to be a requirement to resolve 90% of terrain height variance for mesoscale models, without resorting to the parameterization of subgrid-scale terrain variance. Comparison among results of different simulations shows that the simulations estimate the observed precipitation well when using a resolution of 4.1 km or finer. Although the main flow patterns are similar, finer grids produce more complex patterns that show divergence zones, convergence zones and vortices. Horizontal grid size significantly affects the vertical structure of the convective boundary layer. Stronger vertical wind components are simulated for finer grid resolutions. In particular, noticeable sinking airflows over mountains are captured for those model configurations.展开更多
中国气象局乌鲁木齐沙漠气象研究所自2017年开始推进中亚区域快速更新多尺度分析和预报系统RMAPS-CA的研发工作,并在多源资料联合同化技术、参数化方案优化和动力框架调整方面取得了一定的研究成果。在回顾RMAPS-CA业务研发历程的基础上...中国气象局乌鲁木齐沙漠气象研究所自2017年开始推进中亚区域快速更新多尺度分析和预报系统RMAPS-CA的研发工作,并在多源资料联合同化技术、参数化方案优化和动力框架调整方面取得了一定的研究成果。在回顾RMAPS-CA业务研发历程的基础上,重点对雷达反射率同化、高空次网格地形重力波拖曳与近地层阻塞拖曳分离的次网格物理过程、混合地形追随坐标动力框架以及基于贝叶斯模式平均(Bayesian Model Averaging,BMA)方法订正预报产品等方面所取得的研究成果进行综述。针对中亚地区常规观测稀疏且沙漠下垫面范围广等特点,从卫星地面通道同化等方面提出了加强中亚区域数值天气预报业务研发及应用的建议。展开更多
文摘A new method for constructing contours from complicated terrain elevation grids containing invalid data is put forward. By using this method, the topological consistency of contours in groups can be maintained effectively and the contours can be drawn smoothly based on boundaries pre-searching and local correction. An experimental example is given to demonstrate that the contours constructed by this method are of good quality.
文摘Incremental LOD can be transmitted on the network as a stream, then users on the clients can easily catch the skeleton of terrain without downloading all the data from the server. Detailed information in a local part can be added gradually when users zoom it in without redundant data transmission in this procedure. To do this, an incremental LOD method is put forward according to the regular arrangement of grid. This method applies arbitrary sized grid terrains and is not restricted to square ones with a side measuring 2 k + 1 samples. Maximum height errors are recorded when the LOD is preprocessed and it can be visualized with the geometrical Mipmaps to reduce the screen error.
文摘针对格网DEM难以对黄土高原梯田地形进行有效数字表达的问题,基于面向对象思想提出了能够顾及梯田地形的Grid-TIN混合格网DEM(Grid-TIN based DEM,GT-DEM)概念及其数据模型,并阐明其主要特征及与传统DEM的关系。以陕西绥德县辛店沟小流域水平梯田为例,利用现有1∶1万格网DEM、梯田特征点线及其外围边界线,构建出能够充分顾及梯田地形的GT-DEM。研究表明,利用现有格网DEM和梯田地形特征点线构建顾及梯田地形GT-DEM的技术可行。GT-DEM不仅可对研究区全局地形进行粗略表达,而且可对其局部梯田地形进行精细表达。该研究是对如何提高DEM的梯田地形数字表达能力的有益探索,对进一步提高DEM对淤地坝、鱼鳞坑等其他人工地形的数字表达能力具有重要借鉴意义。
文摘【目的】解决现有地形复杂度误差评价方法主观性强、缺少误差解析式的问题。【方法】利用误差传播定律推导了局部高差、局部标准差、局部褶皱度和局部全曲率的中误差表达式,依据复合地形因子误差传递规律构建了复合地形复杂度指标(compound terrain complexity index,CTCI)提取的误差估计模型(error estimation model for CTCI,CEEM)。通过模拟数字高程模型(digital elevation model,DEM)试验验证了该模型的有效性,并采用三个不同地貌区域的实体DEM进行CEEM泛化试验。【结果】在不同噪声影响下,CEEM平均误差、均方差、残差和平均绝对百分比误差最大值分别为-2.1×10^(-3)、7.99×10^(-6)、8.4×10^(-3)和22.8%,决定系数均在0.961以上,CEEM整体误差微小;不同地貌类型的地形复杂度提取误差存在差异,试验统计结果表明误差由大到小依次为高山、中山、丘陵。【结论】CEEM能定量化描述地形复杂度的提取误差,可为不同复杂地形地貌区域提取复合地形复杂度指标提供参考。
基金supported by the Key Research Program of the Chinese Academy of Sciences (Grant No. KZZD-EW-05-01)the special grant (Grant No. 41375052) from the National Natural Science Foundation of Chinafunded by an open project of the State Key Laboratory of Severe Weather (Grant No. 2013LASW-A06)
文摘Terrain characteristics can be accurately represented in spectrum space. Terrain spectra can quantitatively reflect the effect of topographic dynamic forcing on the atmosphere. In wavelength space, topographic spectral energy decreases with decreasing wavelength, in spite of several departures. This relationship is approximated by an exponential function. A power law relationship between the terrain height spectra and wavelength is fitted by the least-squares method, and the fitting slope is associated with grid-size selection for mesoscale models. The monotonicity of grid size is investigated, and it is strictly proved that grid size increases with increasing fitting exponent, indicating that the universal grid size is determined by the minimum fitting exponent. An example of landslide-prone areas in western Sichuan is given, and the universal grid spacing of 4.1 km is shown to be a requirement to resolve 90% of terrain height variance for mesoscale models, without resorting to the parameterization of subgrid-scale terrain variance. Comparison among results of different simulations shows that the simulations estimate the observed precipitation well when using a resolution of 4.1 km or finer. Although the main flow patterns are similar, finer grids produce more complex patterns that show divergence zones, convergence zones and vortices. Horizontal grid size significantly affects the vertical structure of the convective boundary layer. Stronger vertical wind components are simulated for finer grid resolutions. In particular, noticeable sinking airflows over mountains are captured for those model configurations.
文摘中国气象局乌鲁木齐沙漠气象研究所自2017年开始推进中亚区域快速更新多尺度分析和预报系统RMAPS-CA的研发工作,并在多源资料联合同化技术、参数化方案优化和动力框架调整方面取得了一定的研究成果。在回顾RMAPS-CA业务研发历程的基础上,重点对雷达反射率同化、高空次网格地形重力波拖曳与近地层阻塞拖曳分离的次网格物理过程、混合地形追随坐标动力框架以及基于贝叶斯模式平均(Bayesian Model Averaging,BMA)方法订正预报产品等方面所取得的研究成果进行综述。针对中亚地区常规观测稀疏且沙漠下垫面范围广等特点,从卫星地面通道同化等方面提出了加强中亚区域数值天气预报业务研发及应用的建议。
