MM5模式中不同对流参数化方案的比较试验   总被引：58，自引：2，他引：58  

王建捷  胡欣等 《应用气象学报》2001,12(1):41-53

应用MM5中尺度模式, 在60、20和10 km模式分辨率下, 分别选用4种不同对流参数化方案 (KUO方案、GRELL方案、KAIN-FRITSCH方案和BETTS-MILLER方案, 以下简称KU、GR、KF和BM方案) 对1996年8月3~4日石家庄暴雨过程进行数值模拟试验.模拟结果的对比分析及其与观测的比较表明:主要雨带位置对参数化方案并不是十分敏感, 但随分辨率提高, 雨带分布特征的模拟更接近实况; 当分辨率提高到10 km时, 虚假的降水中心也明显增加; 模拟的暴雨中心强度随分辨率的提高而增强并随参数化方案的不同有所变化, 但均比实况偏弱.分析还发现, MM5模式的GR、KF及BM方案的次网格降水对总降水的贡献率随分辨率的提高而减小, 而KU方案的情况则呈现出不合理的缓慢增加态势.虽然4种方案下模拟的水平环流特征有较好的一致性, 但模拟的云物理特征和垂直运动特征还是存在一定差别的, 这种差别对定点、定量降水和天空状况、地面气温、湿度等要素的准确预报都会产生影响.因此, 在预报和模拟中应考虑预报和研究对象的特点来选择对流参数化方案.  相似文献   

A Simple And General Subgrid Model Suitable Both For Surface Layer And Free-Stream Turbulence   总被引：1，自引：1，他引：1  

J. L. Redelsperger  F. Mahé  P. Carlotti 《Boundary-Layer Meteorology》2001,101(3):375-408

A new and general approach is presented to allow standard subgrid schemes to besuitable both for surface layer and free-stream turbulence. Simple modificationsto subgrid schemes are proposed and derived for any vertical stabilityconditions. They are simple to implement in models and are suitable for morecomplicated simulations such as large-eddy simulation with inhomogeneoussurface conditions or complex topography. They are also applicable to mesoscaleand large-scale models. These modifications are physically justified by recentmeasurements of spectra close to the ground. The spectral analysis presentedshows how the energy deficit of blocked turbulence for a given dissipation(`anomalous dissipation') dramatically affects the coefficients to be used insubgrid schemes. As shown for neutral and convective cases with wind shear,these changes allow us to substantially improve the prediction of profiles for themean quantities in the surface layer. Agreement with similarity laws in the unstablecase is found up to about 0.2z_i, for simulated shear, stabilityprofiles and dissipation rates of turbulent kinetic energy.  相似文献   

中国宏观经济的国际评价   总被引：2，自引：0，他引：2  

吴殿廷  武聪颖 《世界地理研究》2001,10(1):104-112,83

本文以世界平均水平为参照系，对中国的宏观经济特征进行概括和评价，中国在经济规模上是发展很快的大国，在经济水平上是不断提高的究国，在经济结构上具有相对完整的国民经济体系和工业经济体系，中国宏观经济的主要问题是第三产业和城镇化严重滞后，经济效益相对低下，行为开支比例太高，而科技教育投入明显不足。  相似文献   

工程岩体断裂构造发育程度的定量评价研究IAEG信息(会讯)   总被引：2，自引：2，他引：2  

陈昌彦  王思敬 《工程地质学报》2001,9(2):145-151

岩体断裂构造发育程度及其均匀性是影响岩体结构类型、岩体质量优劣及岩体稳定性分析以及工程岩体综合分区利用的重要因素, 因此岩体断裂构造发育程度的定量评价具有重要的工程意义。本文以三峡工程永久船闸边坡工程为例, 系统地讨论了工程岩体断裂构造发育程度的评价方法、定量评价指标的确定原则、断裂构造发育程度的分级标准等。研究表明, 根据岩体断裂构造发育特点, 综合运用多层次模糊综合评判法和人工神经网络技术是评价工程岩体断裂构造发育程度的有效方法。  相似文献   

岩土力学数值模拟中力学参数的确定方法   总被引：4，自引：0，他引：4  

兰恒星  伍法权 《世界地质》2001,20(1):66-71

力学参数的选取是进行岩土力学数值模拟的关键，它直接决定了模拟结果的合理性。不同的力学模型需要选取不同的计算参数，经验值在参数的确定过程中具有一定程度的参考价值，几种变形参数和强度参数的现场尺度转化方法解决了室内土工实验参数的现场应用问题，提出了进行力学参数和计算模型合理确定的推断模型的概念，并对推断模型实现的思想和步骤进行了较为详细的讨论。  相似文献   

Distorted Froude‐scaled flume analysis of large woody debris     

Nicholas P. Wallerstein  Carlos V. Alonso  Sean J. Bennett  Colin R. Thorne 《地球表面变化过程与地形》2001,26(12):1265-1283

This paper presents the results of a movable‐boundary, distorted, Froude‐scaled hydraulic model based on Abiaca Creek, a sand‐bedded channel in northern Mississippi. The model was used to examine the geomorphic and hydraulic impact of simplified large woody debris (LWD) elements. The theory of physical scale models is discussed and the method used to construct the LWD test channel is developed. The channel model had bed and banks moulded from 0·8 mm sand, and flow conditions were just below the threshold of motion so that any sediment transport and channel adjustment were the result of the debris element. Dimensions and positions of LWD elements were determined using a debris jam classification model. Elements were attached to a dynamometer to measure element drag forces, and channel adjustment was determined through detailed topographic surveys. The fluid drag force on the elements decreased asymptotically over time as the channel boundary eroded around the elements due to locally increased boundary shear stress. Total time for geomorphic adjustment computed for the prototype channel at the Q₂ discharge (discharge occurring once every two years on average) was as short as 45 hours. The size, depth and position of scour holes, bank erosion and bars created by flow acceleration past the elements were found to be related to element length and position within the channel cross‐section. Morphologies created by each debris element in the model channel were comparable with similar jams observed in the prototype channel. Published in 2001 John Wiley & Sons, Ltd.  相似文献   

一次干冷锋过程的边界层风场结构和尺度分析     

徐玉貌  张少宝  雷霆 《气象科学》1996,(4)

本文利用南京北郊164米气象塔实测资料对一次非降水弱冷锋过程的边界层风场结构一三维风速、横锋向水平散度、湍流通量和能量的时空分布，以及多尺度时空分布进行了计算分析。结果表明，在冷暖空气的过渡区（锋区）风场各参量具有明显的梯度，锋区前线的强上升气流与强冷锋相近，但锋区宽度较强冷锋宽得多，其时间尺度为30分钟，水平距离为35公里。锋面过境对风温场的影响时段为24小时，在这期间，出现阵风浪涌和多种中、小尺度（时间尺度为3－4小时、1－20分钟）的湍涡活动。  相似文献   

ENSO循环的数值模拟(Ⅱ)──变化性及时间尺度选择机制     

杨修群  谢倩 《气象学报》1996,54(6):719-721

利用热带太平洋海气耦合异常模式的３０ａ模拟结果，对模式ＥＮＳＯ的变化性及多重时间尺度过程进行了细致分析，建立了一ＥＮＳＯ循环多重时间尺度过程相互作用的非线性相似（Ａｎａｌｏｇ）模型，并提出了ＥＮＳＯ循环主周期形成的一种可能机制。指出：和观测事实类似，模式ＥＮＳＯ过程确实涉及到三种时间尺度，即３—４ａ主周期振荡（ＬＦ）、准两年振荡（ＱＢ）和年循环（ＡＣ）；其中，ＱＢ过程是线性海气耦合系统的本征模态，年循环（ＡＣ）对其形成没有本质的影响；３—４ａ主周期振荡（ＬＦ）是一非线性系统的自激振荡现象，其形成是线性系统的本征模即ＱＢ过程通过非线性机制尤其是通过大气辐合反馈加热的“单向性”过程在ＱＢ的暖态产生的减频增幅所致；平均年循环（ＡＣ）虽然不能对ＥＮＳＯ循环形成有本质影响，但它可明显影响ＥＮＳＯ循环的具体振幅和位相，使得ＥＮＳＯ循环具有明显的不规则性并对季节循环具有明显的“锁相”特征；ＥＮＳＯ变化性确是ＬＦ、ＱＢ以及ＡＣ多重时间尺度相互作用形成的。本文提出的ＥＮＳＯ循环时间尺度选择机制不仅解释了主周期振荡的形成过程，而且也较好地解释了ＥＮＳＯ变化的谱，因此，这一机制更接近于观测事实。  相似文献   

THE FOUNDATION AND MOVEMENT OF TROPICAL SEMI-GEOSTROPHIC ADAPTATION   总被引：4，自引：0，他引：4       下载免费PDF全文

Chao Jiping  Lin Yonghui 《Acta Meteorologica Sinica》1996,10(2):129-141

The breakdown and foundation of geostrophic balance is one of the important movements inthe mid-and high-latitude atmosphere and oceans.In the tropical area,the value of Coriolis pa-rameter is so small that it is difficult to satisfy the bi-geostrophic equilibrium between the pressureand velocity fields.However,in the tropical area,the zonal velocity of some motions in the atmo-sphere and oceans is large,so the Coriolis force is not small,geostrophic balance can exist in zonaldirection,i.e.semi-geostrophic balance.Furthermore,in the dominant area of Hadley circulationin the atmosphere or the area near the ocean meridional boundary,the meridional velocity is large,so geostrophic balance can also exist in meridional direction.In this paper,the process of the dis-persion of inertial gravity wave and the foundation of semi-geostrophic balance are first discussed.Second,the adjustment process between the velocity and pressure fields after adaptation is alsoviewed,and the scale criterion of the semi-geostrophic adaptation is discussed,i.e.for the motionwith meridional scale greater than the equatorial Rossby radius of deformation,the velocity andpressure fields after adaptation change to fit the initial pressure field;on the contrary,the fieldschange to fit the initial zonal velocity field,and the strength of the fields after adaptation dependson the zonal scale.  相似文献   

农田尺度土壤水分的监测   总被引：7，自引：1，他引：7       下载免费PDF全文

杨诗秀  雷志栋 《水科学进展》1996,7(1):14-19

根据田间试验实测资料分析了田间土壤水分的空间变化特征和时间动态变化,探索了监测农田水分变化时如何确定其合理的取样数目,讨论了农田尺度的土壤水分应如何监测,为节水灌溉,提高田间用水管理水平提供科学依据。  相似文献