A 3D compressible nonhydrostatic dynamic core based on a three-point multi-moment constrained finite-volume (MCV) method is developed by extending the previous 2D nonhydrostatic atmospheric dynamics to 3D on a terrain...A 3D compressible nonhydrostatic dynamic core based on a three-point multi-moment constrained finite-volume (MCV) method is developed by extending the previous 2D nonhydrostatic atmospheric dynamics to 3D on a terrainfollowing grid. The MCV algorithm defines two types of moments: the point-wise value (PV) and the volume-integrated average (VIA). The unknowns (PV values) are defined at the solution points within each cell and are updated through the time evolution formulations derived from the governing equations. Rigorous numerical conservation is ensured by a constraint on the VIA moment through the flux form formulation. The 3D atmospheric dynamic core reported in this paper is based on a three-point MCV method and has some advantages in comparison with other existing methods, such as uniform third-order accuracy, a compact stencil, and algorithmic simplicity. To check the performance of the 3D nonhydrostatic dynamic core, various benchmark test cases are performed. All the numerical results show that the present dynamic core is very competitive when compared to other existing advanced models, and thus lays the foundation for further developing global atmospheric models in the near future.展开更多
A new scheme for the estimation of daily global solar radiation over sloped topography in China is developed based on the Iqbal model C and MODIS cloud fraction. The effects of topography are determined using a digita...A new scheme for the estimation of daily global solar radiation over sloped topography in China is developed based on the Iqbal model C and MODIS cloud fraction. The effects of topography are determined using a digital elevation model. The scheme is tested using observations of solar radiation at 98 stations in China, and the results show that the mean absolute bias error is 1.51 MJ m-2 d-1 and the mean relative absolute bias error is 10.57%. Based on calculations using this scheme, the distribution of daily global solar radiation over slopes in China on four days in the middle of each season （15 January, 15 April, 15 July and 15 October 2003） at a spatial resolution of 1 km×1 km are analyzed. To investigate the effects of topography on global solar radiation, the results determined in four mountains areas （Tianshan, Kunlun Mountains, Qinling, and Nanling） are discussed, and the typical characteristics of solar radiation over sloped surfaces revealed. In general, the new scheme can produce reasonable characteristics of solar radiation distribution at a high spatial resolution in mountain areas, which will be useful in analyses of mountain climate and planning for agricultural production.展开更多
综合利用火星轨道器多源遥感影像数据,构建了火星表面形貌精细建模与自动分类方法。结合摄影测量法与明暗恢复形状法(Shape From Shading,SFS)研究制作了“天问一号”着陆区域的高分辨率三维地形,并通过深度卷积神经网络对着陆区形貌类...综合利用火星轨道器多源遥感影像数据,构建了火星表面形貌精细建模与自动分类方法。结合摄影测量法与明暗恢复形状法(Shape From Shading,SFS)研究制作了“天问一号”着陆区域的高分辨率三维地形,并通过深度卷积神经网络对着陆区形貌类别及其分布进行分类分析。地形剖面分析结果表明,所提出方法制作的高精度地形数据与中、美两国已发布的火星高分辨率数字高程模型(Digital Elevation Model,DEM)产品相比,高程误差均值分别为1.866 m和1.074 m,均具有较高一致性。此外,通过形貌及制图综合分析可以看出,着陆点附近坡度在3°以下,着陆点附近地表的起伏程度不大于30 cm,以此验证了“天问一号”着陆区整体地势平缓、形貌类别较单一,符合探测器安全着陆的需求。国产“天问一号”高分辨率相机数据制作的地形及分类结果可有效应用于着陆及巡视探测区的形貌特征分析,联合HiRISE等多源火星遥感数据,可为后续“祝融号”巡视器科学探测提供重要的基础数据和参考信息。展开更多
Digital terrain models (DTMs) are not commonly used to integrate for landscape spatial analysis. Two dimensional patchcorridormatrix models are prototypes in landscape spatial ecology analysis. Previous studies have m...Digital terrain models (DTMs) are not commonly used to integrate for landscape spatial analysis. Two dimensional patchcorridormatrix models are prototypes in landscape spatial ecology analysis. Previous studies have motivated ecologists to integrate terrain models in landscape analysis through 1) adjusting areas and distance calculations prior computing landscape indices;2) designing new indices to capture topography and 3) searching the possible relationship between topographic characteristics and vegetation patterns. This study presents new indices called Relative number of Topographic Faces (RTF) and Simplicity of topographic Faces (STF) that can be easily computed in a GIS environment, capturing topographical features of landscapes. Digital terrain model was first prepared and topographic units were extracted and installed in computing the suggested indices. Mountainous and rugged topography in Lebanon was chosen on a forested landscape for the purpose of this study. The indices were useful in monitoring changes of topographic features on patch and landscape level. Both indices are ecologically useful if integrated in landscape pattern analysis, especially in areas of rugged terrains.展开更多
基金supported by the National Key Research and Development Program of China (Grant Nos. 2017YFC1501901 and 2017YFA0603901)the Beijing Natural Science Foundation (Grant No. JQ18001)
文摘A 3D compressible nonhydrostatic dynamic core based on a three-point multi-moment constrained finite-volume (MCV) method is developed by extending the previous 2D nonhydrostatic atmospheric dynamics to 3D on a terrainfollowing grid. The MCV algorithm defines two types of moments: the point-wise value (PV) and the volume-integrated average (VIA). The unknowns (PV values) are defined at the solution points within each cell and are updated through the time evolution formulations derived from the governing equations. Rigorous numerical conservation is ensured by a constraint on the VIA moment through the flux form formulation. The 3D atmospheric dynamic core reported in this paper is based on a three-point MCV method and has some advantages in comparison with other existing methods, such as uniform third-order accuracy, a compact stencil, and algorithmic simplicity. To check the performance of the 3D nonhydrostatic dynamic core, various benchmark test cases are performed. All the numerical results show that the present dynamic core is very competitive when compared to other existing advanced models, and thus lays the foundation for further developing global atmospheric models in the near future.
文摘A new scheme for the estimation of daily global solar radiation over sloped topography in China is developed based on the Iqbal model C and MODIS cloud fraction. The effects of topography are determined using a digital elevation model. The scheme is tested using observations of solar radiation at 98 stations in China, and the results show that the mean absolute bias error is 1.51 MJ m-2 d-1 and the mean relative absolute bias error is 10.57%. Based on calculations using this scheme, the distribution of daily global solar radiation over slopes in China on four days in the middle of each season （15 January, 15 April, 15 July and 15 October 2003） at a spatial resolution of 1 km×1 km are analyzed. To investigate the effects of topography on global solar radiation, the results determined in four mountains areas （Tianshan, Kunlun Mountains, Qinling, and Nanling） are discussed, and the typical characteristics of solar radiation over sloped surfaces revealed. In general, the new scheme can produce reasonable characteristics of solar radiation distribution at a high spatial resolution in mountain areas, which will be useful in analyses of mountain climate and planning for agricultural production.
文摘Digital terrain models (DTMs) are not commonly used to integrate for landscape spatial analysis. Two dimensional patchcorridormatrix models are prototypes in landscape spatial ecology analysis. Previous studies have motivated ecologists to integrate terrain models in landscape analysis through 1) adjusting areas and distance calculations prior computing landscape indices;2) designing new indices to capture topography and 3) searching the possible relationship between topographic characteristics and vegetation patterns. This study presents new indices called Relative number of Topographic Faces (RTF) and Simplicity of topographic Faces (STF) that can be easily computed in a GIS environment, capturing topographical features of landscapes. Digital terrain model was first prepared and topographic units were extracted and installed in computing the suggested indices. Mountainous and rugged topography in Lebanon was chosen on a forested landscape for the purpose of this study. The indices were useful in monitoring changes of topographic features on patch and landscape level. Both indices are ecologically useful if integrated in landscape pattern analysis, especially in areas of rugged terrains.
