基于色层图与纹理融合的地形晕渲

针对三维地形晕渲的具体需求和存在问题,提出了一种基于色层图与纹理融合的晕渲方法。根据自定义或色层表主色调插值生成色彩连续的色层图,对地形高程进行着色;在地表材质分块的基础上,通过计算相邻材质边界上的多重纹理坐标,使用多重纹理映射进行融合过渡;最后给出了实验结果。     

基于雷达资料的定量降水预报外推算法试验

摘要：目前贵州在短时临近降水预报客观算法方面研究匮乏,而短时强降水常常给贵州造成严重的洪涝灾害和地质灾害。将短时临近降水预报应用于气象防灾减灾、电网输电线路安全预警、水利防洪自动化方面是未来重要的研究应用方向。本文基于灾害天气短时临近系统（Severe Weather Automatic Nowcast System,SWAN）的定量降水预报(QPF)产品进行0～2小时QPF外推试验研究。利用贵州省地面自动站数据、SWAN 输出的1h-QPF产品、SWAN 1h定量降水估测(QPE)产品。选取2018年3次典型暴雨个例进行试验,采用融合订正技术,利用相似离度算法对降水强度位相进行调整、Weibull分布算法对降水极值分布进行订正、改进后的交叉相关法(Improved Cross-correlation Extrapolation Method,COTREC)进行降水外推预报。通过主客观检验对比,初步说明基于Weibull分布算法的降水极值订正对降水极值分布有很好的模拟效果。融合订正外推的贵州省短时临近定量降水预报产品（Nowcasting precipitation forecast of GuiZhou,下文简写为GZ_NPF）在大于5mm以上量级降水的TS检验中评分更高。GZ_NPF的空报率明显降低,但空报率降低的代价是漏报率相对提高。GZ_NPF总的相对误差减小,格点总降水量与实况总降水量更为接近。试验说明新的融合订正外推算法提高了0～2h短时临近降水的预报能力。     

Spatiotemporal reflectance blending in a wetland environment

To understand the mechanism of wetland cover change with both moderate spatial resolution and high temporal frequency, this research evaluates the applicability of a spatiotemporal reflectance blending model in the Poyang Lake area, China, using 9 time-series Landsat-5 Thematic Mapper images and 18 time-series Terra Moderate Resolution Imaging Spectroradiometer images acquired between July 2004 and November 2005. The customized blending model was developed based on the enhanced spatial and temporal adaptive reflectance fusion model (ESTARFM). Reflectance of the moderate-resolution image pixels on the target dates can be predicted more accurately by the proposed customized model than the original ESTARFM. Water level on the input image acquisition dates strongly affected the accuracy of the blended reflectance. It was found that either of the image sets used as prior or posterior inputs are required when the difference of water level between the prior or posterior date and target date at Poyang Hydrological Station is <2.68 m to achieve blending accuracy with a mean average absolute difference of 4% between the observed and blended reflectance in all spectral bands.     

GRAPES区域集合预报尺度混合初始扰动构造的新方案

集合预报初始扰动能否准确反映预报误差的结构特征是决定区域集合预报质量的关键因素之一。本文针对GRAPES区域数值预报模式,发展设计了一种基于资料同化思想的混合尺度初始扰动构造新方案。该方案以全球大尺度信息为背景场,区域模式预报作为观测资料,借助GRAPES三维变分同化系统,将高质量的全球大尺度信息与区域模式预报中质量较高的中小尺度信息有效融合,构造混合尺度区域集合预报初始扰动,并通过个例试验和批量试验,比较分析了新方案和原区域集合预报的性能。试验结果表明,基于资料同化构造的初始扰动能够有效融合全球大尺度信息和中小尺度天气系统的信息,其降水概率预报更具参考价值。总体上看,区域集合预报混合初始扰动新方案能够较好地改进区域集合预报质量,尤其是对高度场和温度场效果更为显著,但对风场的集合预报性能影响略小。     

An Implementation of Full Cycle Strategy Using Dynamic Blending for Rapid Refresh Short-range Weather Forecasting in China

The partial cycle(PC) strategy has been used in many rapid refresh cycle systems(RRC) for regional short-range weather forecasting. Since the strategy periodically reinitializes the regional model(RM) from the global model(GM)forecasts to correct the large-scale drift, it has replaced the traditional full cycle(FC) strategy in many RRC systems.However, the extra spin-up in the PC strategy increases the computer burden on RRC and generates discontinuous smallscale systems among cycles. This study returns to the FC strategy but with initial fields generated by dynamic blending(DB) and data assimilation(DA). The DB ingests the time-varied large-scale information from the GM to the RM to generate less-biased background fields. Then the DA is performed. We applied the new FC strategy in a series of 7-day batch forecasts with the 3-hour cycle in July 2018, and February, April, and October 2019 over China using a Weather Research and Forecast(WRF) model-based RRC. A comparison shows that the new FC strategy results in less model bias than the PC strategy in most state variables and improves the forecast skills for moderate and light precipitation. The new FC strategy also allows the model to reach a balanced state earlier and gives favorable forecast continuity between adjacent cycles. Hence, this new FC strategy has potential to be applied in RRC forecast systems to replace the currently used PC strategy.     

雷达资料和数值模式产品融合技术研究

以雷达外推为基础,配合中尺度数值模式产品作为环境场,提出两种新的雷达资料和数值模式融合技术:动态权重融合法和趋势演变叠加法。且在动态权重融合法中提出用正弦权重、双曲正切权重以及实时滚动权重三种方法计算权重。使用上海及周边地区2009年6月21日的一次对流过程进行个例分析及误差检验,结果表明:利用这两种方法进行融合后的预报结果与雷达外推和数值模式预报结果相比均有所改进,特别是动态权重融合法中的正弦权重和双曲正切权重对于预报结果的改进尤为明显,融合后的结果更接近实况,表明动态权重融合法和趋势演变叠加法这两种方法是有效可行的,对短时临近预报技术研究有较高的参考价值。     

陕北高挥发分烟煤煤质特征与应用研究

通过煤质分析、煤岩分析与葛-金干馏试验等对比实验，研究了陕北横山、神府矿区等地侏罗纪不粘-弱粘煤及其配煤的煤炭特性、低温干馏特性以及单种煤与配煤低温干馏性能差异和变化规律。结果表明，陕北侏罗纪煤具有较高的焦油产率，配煤在降低煤中含硫量的同时，有利于低温干馏过程的进行和产品质量的提高；此外，在掌握原煤显微组成和低温干馏特性的情况下，可以预测配煤低温干馏产品的相关参数。     

基于OpenGL城市大规模管网三维建模

城市管网是城市建设的重要组成部分。本文讨论了基于OpenGL的大规模城市管网三维建模技术,从介绍世界坐标系和局部坐标系的转换关系出发,重点介绍了管网的直线部分建模和管网衔接处的建模,提出了一种基于顶点混合技术来绘制管网衔接处的新算法,该算法方便高效,能产生逼真的效果,并给出了加快三维显示速度的方法,实现了城市管网的大规模实时建模。     

Study on multi-scale blending initial condition perturbations for a regional ensemble prediction system

An initial conditions (ICs) perturbation method was developed with the aim to improve an operational regional ensemble prediction system (REPS). Three issues were identified and investigated: (2) the impacts of perturbation scale on the ensemble spread and forecast skill of the REPS; (3) the scale characteristic of the IC perturbations of the REPS; and (4) whether the REPS's skill could be improved by adding large-scale information to the IC perturbations. Numerical experiments were conducted to reveal the impact of perturbation scale on the ensemble spread and forecast skill. The scales of IC perturbations from the REPS and an operational global ensemble prediction system (GEPS) were analyzed. A "multi-scale blending" (MSB) IC perturbation scheme was developed, and the main findings can be summarized as follows: The growth rates of the ensemble spread of the REPS are sensitive to the scale of the IC perturbations; the ensemble forecast skills can benefit from large-scale perturbations; the global ensemble IC perturbations exhibit more power at larger scales, while the regional ensemble IC perturbations contain more power at smaller scales; the MSB method can generate IC perturbations by combining the small-scale component from the REPS and the large-scale component from the GEPS; the energy norm growth of the MSB-generated perturbations can be appropriate at all forecast lead times; and the MSB-based REPS shows higher skill than the original system, as determined by ensemble forecast verification.     

降水临近预报及其在水文预报中的应用研究进展

随着全球气候变化、自然变迁及陆表生境改变,极端天气频发且呈现出多尺度时空变异特征,对其进行预报和预警一直是气象水文领域关注的焦点。临近预报可较准确地预报未来短时间天气显著变化,是当前预报强降水等极端事件的主要手段。从基于天气雷达0～3 h外推临近预报、融合数值模式0～6 h临近预报的发展历程梳理了临近预报的研究进展,阐述了雷达外推算法的发展进程、雷达外推预报与数值模式预报融合技术进展,指出"取长补短"的0～6 h融合预报在提高降水预报精度、延长降水预见期等多方面有较大的发展潜力,进一步探寻及提升融合技术是未来融合预报发展的核心。将临近预报以气象水文耦合的方式引入水文预报是从源头提高水文预报精度、保障水文预报效果的主要途径,总结了现阶段主流耦合方式、空间尺度匹配技术、水文模型不确定等陆气耦合中的关键问题,阐述了外推临近预报、融合临近预报作为水文预报输入的研究进展,明确了融合临近预报在延长洪水预见期、提高洪水预报精度中存在优势,并讨论了未来的研究重点及发展方向。