基于气温的浮冰侧向融化速率参数化方案实验研究   总被引：3，自引：3，他引：0  

艾润冰  谢涛  刘彬贤  赵立  方贺 《海洋学报》2020,42(5):150-158

为定量探究影响冰层侧向融化的主导因素，并简化冰层侧向融化速率参数化方案，在实验室模拟了无风、静水、无辐射、纯热力学条件下纯水冰的融化过程，测量了冰层的侧向融化量，并记录了融化期间实验室气温、冰面皮温、水温及冰温等要素。观测结果表明，无辐射纯热力学条件下冰层侧向融化整体较均匀，侧向上层和下层融化速率相对中间层较快；相关性分析结果表明，气温与水温、冰温、冰面皮温之间都有很好的线性相关；信息流结果表明，气温是影响冰层侧向融化的最主要因素；最后通过拟合建立了用气温表征冰层侧向融化速率的参数化方案，并与前人的方案进行了比较，结果显示本文参数化方案模拟效果较好，所得标准偏差最小，为0.08 mm/h，达到了简化参数的目的。  相似文献   

Accelerating shear velocity in gravel-bed channels     

HOSSEIN AFZALIMEHR  FRANÇOIS ANCTIL 《水文科学杂志》2013,58(1):113-124

Abstract

The behaviour of the shear velocity along a gravel-bed channel is investigated experimentally in the presence of a negative pressure gradient (accelerating flow). Different methods of estimation of the shear velocity, derived from vertical profiles of the mean longitudinal point velocity, are examined and a new method is proposed. Results show that the proposed method of estimation is comparable to the St Venant and Clauser's methods. At a specific cross section, for constant bottom slope and relative roughness, shear velocity increases with discharge.  相似文献   

不同物理过程参数化方案对贵州降水预报的敏感性试验   总被引：8，自引：1，他引：8  

伍红雨  陈德辉  徐国强 《气象》2007,33(4):23-28

利用我国新一代数值预报模式GRAPES，采用6个不同的参数化方案组合：即选择Kessler、NCEP3_class simple ice和simple ice（developed by LiuQijun，CAMS）微物理过程参数化方案和Kain-Fritseh（new Eta）、Betts-Miller-Janjie积云参数化方案形成6个组合，对2004年贵州汛期的降水过程进行48小时的预报试验，对预报结果进行对比分析并与实况资料进行比较、检验。结果表明：GRAPES模式适合对贵州的降水预报；积云参数化方案对降水的影响比微物理过程参数化方案对降水的影响大。simpleice方案与Betts-Miller-Janjie方案组合对贵州降水的预报较好，这些结果对提高GRAPES模式对贵州降水的预报能力有一定的参考意义。  相似文献   

用于声波方程数值模拟的时间-空间域有限差分系数确定新方法   总被引：4，自引：4，他引：0       下载免费PDF全文

梁文全  杨长春  王彦飞  刘红伟 《地球物理学报》2013,56(10):3497-3506

声波方程数值模拟已广泛应用于理论地震计算,同时构成了地震逆时偏移成像技术的基础.对于有限差分法而言,在满足一定的稳定性条件时,普遍存在着因网格化而形成的数值频散效应.如何有效地缓解或压制数值频散是有限差分方法研究的关键所在.为精确求解空间偏导数,相继发展了高阶差分格式优化方法和伪谱方法.近期,为更好地缓解数值频散,提出了时间-空间域有限差分方法,该方法采用了泰勒展开近似方法来确定有限差分格式系数,因而只能保证在一定的小范围内很好的拟合波场传播规律.为进一步压制数值频散效应,本文引入了时间-空间域特定波数点满足频散关系的方法,根据震源、波速和网格间距确定波数范围,同时考虑了多个传播角度,然后建立方程确定了相应的有限差分格式系数,使得差分系数能在更大范围符合波场传播规律.通过频散分析和正演模拟,验证了本文方法的有效性.  相似文献   

最优化辛格式广义离散奇异核褶积微分算子地震波场模拟   总被引：2，自引：2，他引：0       下载免费PDF全文

刘少林  李小凡  汪文帅  鲁明文  张美根 《地球物理学报》2013,56(7):2452-2462

将波动方程变换至Hamilton体系,构造了一种新的保结构算法,即最优化辛格式广义褶积微分算子(OSGCD). 在时间离散上,首先引入了Lie算子设计二级二阶辛格式,基于最小误差原理得到了优化的辛格式. 在空间离散上,引入广义离散奇异核褶积微分算子计算空间微分,提出了一种有效方法优化GCD并得到了稳定的算子系数. 针对本文发展的新方法,给出了OSGCD稳定性条件. 在数值实验中,将OSGCD与多种方法比较,从精度和计算效率两方面分析了OSGCD的计算优势,计算结果也表明OSGCD长时程以及非均匀介质中地震波模拟亦具有较强能力.  相似文献   

Simulation of dam-break waves on movable beds using a multi-stage centered scheme     

Stefania EVANGELISTA  Mustafa S.ALTINAKAR  Cristiana DI CRISTO  Angelo LEOPARDI 《国际泥沙研究》2013,28(3):269-284

This paper presents the application of the multi-stage first-order centered scheme GMUSTA to solve a two-phase flow model with four equations for simulating dam-break floods without and with sediment transport.Computation of generalized Riemann invariants can be particularly complex and costly in simulating dam-break floods with sediment transport.GMUSTA numerical scheme,which does not require complete knowledge of the eigenstructure of the hyperbolic mathematical model,offers a suitable and attractive option.The quality of the dam-break flood simulations with GMUSTA scheme is verified by comparing the results against laboratory tests and some experimental data available in the literature,on fixed and mobile bed conditions,with different bed materials and flush or stepped bottoms.The numerical results reproduce quite well the experimental evidence,proving that the model is capable of predicting the temporal evolution of the free-surface and the bed.The GMUSTA scheme,which is not only simple to implement but also both accurate and computationally efficient,is proposed as an appropriate tool for integrating non-equilibrium sediment-transport models.  相似文献   

A hillslope-based hydrological model using catchment area and width functions     

DAWEN YANG  SRIKANTHA HERATH  KATUMI MUSIAKE 《水文科学杂志》2013,58(1):49-65

Abstract

A flow-interval hillslope discretization scheme is proposed for catchment hydrological modelling. By this scheme, a two-dimensional catchment is simplified into a one-dimensional cascade of flow intervals linked by the main stream. Each flow interval comprises a set of parallel hillslopes. The hillslope is the fundamental computational unit in the hydrological model providing lateral inflow to the main stream. The size of hillslope is determined by the catchment area and width functions. Catchment runoff is the total of hillslope responses through the river routing. Tests in four Japanese catchments showed that the model performed well on simulating the overall water balance, general flow pattern, and daily and hourly hydrographs of a whole catchment, as well as simultaneous simulation in different subcatchments. Characteristics of catchment hydrological responses and model applicability are discussed.  相似文献   

A perception-based color recommendation algorithm for hierarchical regions     

Shipeng Sun 《制图学和地理信息科学》2013,40(3):259-270

The visualization of hierarchical and nested spatial regions remains a challenge to cartographers. Despite progress in computer algorithms for visualizing general hierarchical data, mapping spatial hierarchical regions, especially with static, noninteractive means, still requires considerable manual efforts. This paper proposes a two-step algorithm that can automatically recommend perception-based colors and help reveal the hierarchical structure embedded in nested regions. It first systematically sorts regions according to their contiguity and containment relations at multiple hierarchical levels. Then, perception-based colors are generated using the order of regions with the goal of maximizing differentiability between top-level regions while retaining the perceived uniformity of the bottom-level regions. With the coloring scheme recommended by this algorithm, the metric color differences among regions mathematically reflect their hierarchical positions and spatial relations. The resultant colors, therefore, can potentially help map-readers perceive the spatially constrained hierarchy structure built in nested regions.  相似文献   

两种陆面方案对陆雾与海雾模拟效果的对比研究          下载免费PDF全文

姜昊宇  高山红 《海洋气象学报》2021,41(1):30-44

利用WRF(Weather Research and Forecasting)模式,针对1次陆雾与1次同时包含近海雾区与开阔海域雾区的海雾个例,开展了2种陆面方案——SLAB(five-layer thermal diffusion scheme)方案与Noah(Noah land surface scheme)方案——的模拟效果对比研究。研究结果表明:1)SLAB方案与Noah方案在开阔海域雾区模拟中的表现基本一致,但只有前者成功再现了陆雾与近海雾区。2)对于陆雾,与SLAB方案相比,Noah方案在白天偏高的地表温度造成偏强的地面垂直热量通量,加之偏弱的垂直水汽通量共同使得地面相对湿度偏低20%,导致模拟失败。3)对于海雾,两种方案模拟的地表温度与地面垂直水汽通量之间的差异,直接导致了地面2 m气温与水汽混合比的差异,进而影响了渤海的地面低压天气系统的强弱与水汽平流的大小,从而使得它们对渤海近海雾区的模拟表现迥异。本次个例中,应用广泛且陆面过程完善的Noah方案对陆雾模拟的表现反而不如过程简单的SLAB方案,本文对此给出了初步的解释,但仍需进一步探究其原因。  相似文献   

基于自主体的全球碳交易模拟     

朱潜挺  吴静  王铮 《地理研究》2012,31(9):1547-1558

碳交易是未来全球应对气候变化的重要组成部分之一。基于Agent建模技术,开发了一个包含中国、美国、日本、欧盟、前苏联地区以及世界其他地区的全球碳交易模拟系统,并且根据人均累积排放权均等和减排目标控制原则,设置了"丁标准"情景和"2℃目标"情景,对全球碳交易行为展开了模拟研究。研究发现:(1)随着碳排放权的逐年减少,未来碳交易价格将呈上升趋势;(2)碳交易将有助于资金从发达国家向发展中国家转移;(3)由于碳交易允许配额缺口区域向配额盈余区域购买碳排放权,未来发达国家的人均碳排放量仍将高于发展中国家;(4)虽然碳交易能提高全球累计拉姆齐效用,但无论从中国在未来碳市场中的收支情况,还是全球福利水平的改善程度来看,"2℃目标"情景均将优于"丁标准"情景。  相似文献