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4地图设影地球可近似看成球体，在球面坐标中，地球表面任意一点的位置用经度λ、纬度来确定。投影变换将球面坐标转换成平面直角坐标，五常见的投影变换有兰勃托四谁投影、麦卡托四往投影和极射赤面投影。通常欧亚国使用兰勃托投影、热带团使用麦卡托投影。4．1兰勃托投影用一键项位于地球自转轴上的圆锥面与地球上的两个标准纯白叩；、叶相割，点光源位于地球中心，中央纬四队和中央经留人的交点决定投影平面上直角坐标系的原点，如图6。4．2麦卡托投影用一圆柱面与地球表面相切于赤道平面，点光源在地球中心（如图7），因此，其中R”为… 相似文献
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利用清代档案资料，复原了1755年和1849年苏皖地区的洪涝实况，并对其特征进行对比分析，同时探讨了洪涝发生的可能原因。结果表明：1755年雨季持续时间长，春、夏、秋3季都发生大涝，淮河以北及江淮地区尤为严重；而1849年雨期提前，大雨多发，长江沿江和长江以南地区洪涝严重；1755年和1849年是苏皖地区历史上非常严重的洪涝年，其洪涝程度可与该地区20世纪所出现的特大洪涝灾害相比拟；另外，本文还初步探讨了1755年和1849年洪涝与ENSO和太阳活动之间的关系。 相似文献
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基于GIS的洪涝灾害遥感评估系统 总被引：1，自引：0，他引：1
利用NOAA／AVHRR气象卫星实时监洲到的洪涝灾害数据与GIS技术相结合，以地理信息系统软件AreView3．1为依托建立洪涝灾害遥感评估系统。系统可提供洪涝区域内居民区的受淹数据，并进行受淹区域的比例系数计算，提供水田、旱田、林地、灌丛、果树和草地等淹没面积的信息。 相似文献
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以微波辐射传输模式为基础，正演模拟分析星载先进微波探测器（AMSU）窗区通道微波亮温对地表洪涝信息的敏感性，结果表明中心频点分别为31.4、50.3和89.0 GHz的AMSU窗区通道2、3和15的微波亮温对地表洪涝特征敏感；以正演模拟计算结果为基础，选择对地表洪涝特征敏感的AMSU窗区通道为因子，组合形成AMSU洪涝指数AFI(AMSU Flooding Index)，进行地表洪涝区分类研究；地表洪涝分类结果与经机-地校验过的机载合成孔径雷达L-SAR资料分析结果进行对比分析，分类正确率可达73%。短时监测试验结果表明，应用美国第5代极轨业务环境卫星上装载的先进微波探测器（AMSU）微波资料可以在准全天候条件下，实现区域地表洪涝区分类实时监测，有效弥补红外和可见波段洪涝遥感探测技术在云天条件下无法实施的缺陷。 相似文献
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为了揭示武义县暴雨洪涝的时空变化特征，基于1970-2018年洪涝及暴雨实测数据，统计分析反映时空变化特征的一系列指标，应用多元线性回归模型，建立水位与径流、降雨的多元相关关系。研究结果表明：洪涝在20世纪70至80年代中期次数偏少，其后开始逐渐增多，且具有3a左右的年际周期变化，12a左右和25a左右的年代际周期变化；洪涝主要发生在主汛期6-8月，其中，6月中旬至7月中旬以系统性暴雨为主，洪涝占全年60%，7月下旬至8月短时暴雨明显增多，山洪占全年50%；洪涝与西部型南亚高压、西太平洋副热带高压的变化特征正相关，同时中低层冷暖气流的汇合强度亦有利于产生洪涝；构建武义江流域水位与径流、降雨多元逐步回归模型，提出一种以水位预报为目标的洪水趋势预测方法。 相似文献
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水域面积是生态与农业气象业务中的重要基础数据之一,同时也是遥感业务化监测的重要内容之一。将地理信息系统技术引入到水域面积遥感动态监测业务中。对遥感数据的投影方式和投影参数进行了进一步的规范和统一;设计和实现了水域面积监测地理信息数据库;建立了基于地理信息系统的人机交互水域面积提取方法;建立了统一的制图模板,提高了水域面积遥感动态监测能力,取得了较好的应用效果。 相似文献
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火箭、高炮作业指挥盘的研制及应用 总被引：1，自引：0，他引：1
1 设计原理 指挥盘设计的基本思想是 ,将以雷达为中心的坐标系统和以作业点为中心的坐标系统同时投影在一张底图上。这样 ,在雷达坐标系统中确定目标云位置后 ,就可以很快在作业点坐标系统中确定其方位和距离。并使用了直观的球面投影方式进行投影。同时 ,为了便于查找作业仰角 ,将相应作业工具的弹道图或表统一成Ａ—Ｈ—Ｌ曲线 (仰角—高度—距离 ) ,一并打印在底图上 ,根据作业高度和作业距离就可迅速查找到作业仰角。( 1 )底图 底图由射程圆和两个预警圆组成 ,用于完成作业指挥及指挥前的预警识别。底图正中是作业点的射程圆 ,上方… 相似文献
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赣湘辽吉洪涝严重陕甘宁晋干旱缓解－１９９５年７月－徐良炎（国家气候中心，北京１０００８１）本月上旬，北方降雨偏少，陕、甘、宁、晋等地旱情发展；南方降雨偏多，赣、湘等省洪涝加重。中下旬，北方降雨偏多，西北、华北旱情缓解，东北南部暴雨成灾；南方酷热少雨，... 相似文献
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Z. Jaňour 《Boundary-Layer Meteorology》1975,9(1):3-10
The wavy area of north-west Bohemia (Czechoslovakia) is simulated by a cylindrical surface model. A curvilinear orthogonal system of coordinates along the model surface is introduced. The hydrodynamical equations of motion are transformed into this system of coordinates. By applying boundary-layer assumptions, the equations of motion for the atmospheric boundary layer (ABL) above the model are derived. The equations and boundary conditions show an equivalence of the ABL above the model with that above a flat surface with external pressure gradient. 相似文献
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为提高机械零件尺寸检测的精度,针对Tsai两步标定法中初始参数不精确的问题,提出了基于直线投影约束的三步标定方法.该方法首先利用直线投影约束条件求解出图像中心点和畸变参数的初始值,然后结合径向排列约束条件求解超定方程组得出全部外部参数和余下内部参数值,最后对全局参数进行非线性优化.为验证提出方法的效果,通过建立基于图像模板的世界坐标系实现,即首先利用图像像素坐标求取摄像机坐标,再将摄像机坐标进行归一化,利用外参数矩阵就可以求解出图像点的世界坐标.结果表明,该方法可以有效提高摄像机标定的精度,像素误差可达0.126 5像素点,单目视觉尺寸检测中任意两点距离误差小于0.41%. 相似文献
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Hann-Ming H. Juang 《Meteorology and Atmospheric Physics》1992,50(1-3):75-88
Summary The set of fully compressible nonhydrostatic equations governing a broad spectrum of atmospheric motion was transformed fromz coordinates to sigma coordinates under a hydrostatic base state. The hydrostatic base state may be either time-independent, such as a hydrostatic balance with-out motion or with motion such as a thermal wind balance, or time-dependent such as might be obtained from the result of integrating a hydrostatic model. The transformed set of equations can be used to predict and study all scales of at mospheric phenomena.The set of perturbation equations was also derived under the same condition. The computational sensitivity in computation of pressure gradient force in sigma coordinate can be improved by computing the pressure gradient interms of perturbations under a certain hydrostatic state.The hydrostatic regional spectral model developed by Juang and Kanamitsu (1991) was modified to be a nonhydrostatic spectral model based on the nonhydrostatic equations in sigma coordinates with time-dependent hydrostatic base states. A semi-implicit time integration scheme was used. Two experiments were performed to test this nonhydrostatic spectral model with acceptable results.With 7 Figures 相似文献
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Luo Zhexian 《Acta Meteorologica Sinica》1996,10(1):13-21
By using the linearized barotropic vorticity equation in polar coordinates the stability of perturbations on a large scale circular basic flow is transformed into a generalized eigenvalue problem,yielding the relationship between the growth rate of the amplitude of perturbations and the azimuthal wave number. Then, numerical experiments whose integration time is 60 model hours are performed in terms of a quasi-geostrophic barotropic model in Cartesian coordinates using the perturbation stream function field of unstable mode superimposed on a strong and weak circular basic flows as the initial fields. The experimental results reveal that the amplitudes of the initial perturbations in the model atmosphere grow with time. The amplitude of the perturbations superimposedon the strong circular basic flow grows quicker and forms a spiral-band-like structure. 相似文献
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Paul N. Swarztrauber David L. Williamson John B. Drake 《Dynamics of Atmospheres and Oceans》1998,27(1-4)
Cartesian coordinates are used to solve the nonlinear shallow-water equations on the sphere. The two-dimensional equations, in spherical coordinates, are first embedded in a three-dimensional system in a manner that preserves solutions of the two-dimensional system. That is, solutions of the three-dimensional system, with appropriate initial conditions, also solve the two-dimensional system on the surface of the sphere. The higher dimensional system is then transformed to Cartesian coordinates. Computations are limited to the surface of the sphere by projecting the equations, gradients, and solution onto the surface. The projected gradients are approximated by a weighted sum of function values on a neighboring stencil. The weights are determined by collocation using the spherical harmonics in trivariate polynomial form. That is, the weights are computed from the requirement that the projected gradients are near exact for a small set of spherical harmonics. The method is applicable to any distribution of points and two test cases are implemented on an icosahedral geodesic grid. The method is both vectorizable and parallelizable. 相似文献
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Small water bodies create their own characteristic local meteorological environments. The heat and water budgets will generally vary with surface area and water depth. If a small pond gradually becomes covered by vegetation, its meteorological conditions will change. On occasion, a vegetated area may change into a pond, complete with vegetation established in the water and extending above the surface. Such are beaver ponds and other flooded areas. The paper discusses the main features of the development of beaver ponds and their heat and water budgets at different stages. The energy budget programme used was previously developed by the authors, but it has been modified to account for the different phases of the pond development. The effects of the various physical changes are evaluated by comparing the individual heat and water budget terms for different stages between an open lake surface and a forest cover. The local heat budget will only be affected on a small scale by the establishment of a beaver pond, but the influence on the water budget has far‐reaching consequences. 相似文献
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An Impact Study of the Vertical Coordinate on a Non-hydrostatic Mesoscale High-Resolution Model 
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下载免费PDF全文 With the high-speed development of high-powered computer techniques, it is possible that a high-resolution and multi-scale unified numerical model is applied to the operational weather prediction. Some techniques about mesoscale non-hydrostatic numerical weather prediction are addressed, and the impact of the vertical coordinate system is one of them. Based on WRF (Weather Research and Forecasting) model, the influence of vertical coordinates on the non-hydrostatic mesoscale high-resolution model is compared. The results show that the error of various coordinates in lower levels is almost same when we use the geometry height (z) and the pressure (p) to set up a terrain-following coordinate; but the error of the height terrain-following coordinate in higher levels is smaller than that of the pressure terrain-following coordinate. The higher the resolution is, the bigger the error will be. The results of the high-resolution simulation exhibited that the trend of the difference in the two coordinates existed. In addition, the correlative coefficient and standard error are also analysed by the comparison between the forecast fields and the corresponding analysis fields. 相似文献
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罗哲贤 《Acta Meteorologica Sinica》1996,(1)
By using the linearized barotropic vorticity equation in polar coordinates the stability of pertur-bations on a large scale circular basic flow is transformed into a generalized eigenvalue problem,yielding the relationship between the growth rate of the amplitude of perturbations and the az-imuthal wave number. Then, numerical experiments whose integration time is 60 model hours areperformed in terms of a quasi-geostrophic barotropic model in Cartesian coordinates using the per-turbation stream function field of unstable mode superimposed on a strong and weak circular basicflows as the initial fields. The experimental results reveal that the amplitudes of the initial pertur-bations in the model atmosphere grow with time. The amplitude of the perturbations superimposedon the strong circular basic flow grows quicker and forms a spiral-band-like structure. 相似文献
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气象卫星遥感洪涝面积估算 总被引：4，自引：4，他引：4
本文介绍了应用ＮＯＡＡ极轨气象卫星ＡＶＨＲＲ资料估算洪涝面积的原理和技术方法。应用气象卫星遥感资料，结合地理信息和实陆调查资料，通过计算分析和图像处理，可以实时、客观地判断洪涝灾害范围，区分洪涝程度，计算受灾面积。 相似文献