Improvement of the semi-Lagrangian advection scheme in the GRAPES model: Theoretical analysis and idealized tests   总被引：2，自引：0，他引：2  

HUANG Bo  CHEN Dehui  LI Xingliang  LI Chao 《大气科学进展》2014,31(3):693-704

ABSTRACT The Global/Regional Assimilation and PrEdiction System （GRAPES） is the newgeneration numerical weather predic- tion （NWP） system developed by the China Meteorological Administration. It is a fully compressible non-hydrostatical global/regional unified model that uses a traditional semi-Lagrangian advection scheme with cubic Lagrangian interpola tion （referred to as the SL_CL scheme）. The SL_CL scheme has been used in many operational NWP models, but there are still some deficiencies, such as the damping effects due to the interpolation and the relatively low accuracy. Based on Reich＇s semi-Lagrangian advection scheme （referred to as the R2007 scheme）, the Re_R2007 scheme that uses the low- and high-order B-spline function for interpolation at the departure point, is developed in this paper. One- and two-dimensional idealized tests in the rectangular coordinate system with uniform grid cells were conducted to compare the Re..R2007 scheme and the SL_CL scheme. The numerical results showed that： （1） the damping effects were remarkably reduced with the Re_R2007 scheme; and （2） the normalized errors of the Re_R2007 scheme were about 7.5 and 3 times smaller than those of the SL_CL scheme in one- and two-dimensional tests, respectively, indicating the higher accuracy of the Re..R2007 scheme. Furthermore, two solid-body rotation tests were conducted in the latitude-longitude spherical coordinate system with non uniform grid cells, which also verified the Re_R2007 scheme＇s advantages. Finally, in comparison with other global advection schemes, the Re_R2007 scheme was competitive in terms of accuracy and flow independence. An encouraging possibility for the application of the Re_R2007 scheme to the GRAPES model is provided.  相似文献   

冬季黄海暖流西偏机理数值探讨   总被引：1，自引：0，他引：1  

邢传玺  黄大吉 《海洋学报》2010,32(6):1-10

利用海洋数值模式(MITgcm)模拟了冬季黄海流场并对冬季黄海暖流西偏的机理进行了探讨。冬季黄海流场模拟试验表明,黄海暖流由济州岛以西约32.5°N,125°E附近进入黄海,然后沿着黄海深槽西侧70 m等深线附近向北偏西运动;海面高度调整对黄海暖流路径具有重要影响,沿着黄海暖流路径的海面高度梯度比周围海区大,由海面高度梯度产生的地转流引起的北向体积输运占总的北向体积输运的78%。狭长海湾地形控制试验表明,单纯的黄海地形分布不足以引起黄海暖流西偏。黄海典型断面试验与渤海、黄海、东海地形控制试验说明,黄海暖流进入黄海的地理位置对流场分布有重要影响,黄海暖流进入黄海的位置恰好位于深槽西侧地形坡度较大区域,在位涡守恒的约束下黄海暖流受地形捕获沿70 m等深线附近向北偏西运动;试验还表明,黄海暖流进入黄海的位置与东海北部环流和地形分布有关,在冬季风的作用下东海北部环流的一部分沿着地形陡坡进入黄海形成黄海暖流。由此认为,黄海、东海环流在其特殊地形的约束下对冬季风的响应和调整,是引起黄海暖流西偏的主要原因。  相似文献   

Calibration and use of continuous heat-type automated seepage meters for submarine groundwater discharge measurements     

B.M. Mwashote  W.C. Burnett  J. Chanton  I.R. Santos  N. Dimova  P.W. Swarzenski 《Estuarine, Coastal and Shelf Science》2010

Submarine groundwater discharge (SGD) assessments were conducted both in the laboratory and at a field site in the northeastern Gulf of Mexico, using a continuous heat-type automated seepage meter (seepmeter). The functioning of the seepmeter is based on measurements of a temperature gradient in the water between downstream and upstream positions in its flow pipe. The device has the potential of providing long-term, high-resolution measurements of SGD. Using a simple inexpensive laboratory set-up, we have shown that connecting an extension cable to the seepmeter has a negligible effect on its measuring capability. Similarly, the observed influence of very low temperature (≤3 °C) on seepmeter measurements can be accounted for by conducting calibrations at such temperatures prior to field deployments. Compared to manual volumetric measurements, calibration experiments showed that at higher water flow rates (>28 cm day⁻¹ or cm³ cm⁻² day⁻¹) an analog flowmeter overestimated flow rates by ≥7%. This was apparently due to flow resistance, turbulence and formation of air bubbles in the seepmeter water flow tubes. Salinity had no significant effect on the performance of the seepmeter. Calibration results from fresh water and sea water showed close agreement at a 95% confidence level significance between the data sets from the two media (R² = 0.98). Comparatively, the seepmeter SGD measurements provided data that are comparable to manually-operated seepage meters, the radon geochemical tracer approach, and an electromagnetic (EM) seepage meter.  相似文献   

Peat porewater chloride concentration profiles in the Everglades during wet/dry cycles from January 1996 to June 1998: field measurements and theoretical analysis     

Michael M. Reddy  Micaela B. Reddy  Kenneth L. Kipp  Aaron Burman  Paul Schuster  Peter S. Rawlik Jr. 《水文研究》2008,22(11):1713-1724

Water quality is a key aspect of the Everglades Restoration Project, the largest water reclamation and ecosystem management project proposed in the United States. Movement of nutrients and contaminants to and from Everglades peat porewater could have important consequences for Everglades water quality and ecosystem restoration activities. In a study of Everglades porewater, we observed complex, seasonally variable peat porewater chloride concentration profiles at several locations. Analyses and interpretation of these changing peat porewater chloride concentration profiles identifies processes controlling conservative solute movement at the peat–surface water interface, that is, solutes whose transport is minimally affected by chemical and biological reactions. We examine, with an advection–diffusion model, how alternating wet and dry climatic conditions in the Florida Everglades mediate movement of chloride between peat porewater and marsh surface water. Changing surface water–chloride concentrations alter gradients at the interface between peat and overlying water and hence alter chloride flux across that interface. Surface water chloride concentrations at two frequently monitored sites vary with marsh water depth, and a transfer function was developed to describe daily marsh surface water chloride concentration as a function of marsh water depth. Model results demonstrate that porewater chloride concentrations are driven by changing surface water chloride concentrations, and a sensitivity analysis suggests that inclusion of advective transport in the model improves the agreement between the calculated and the observed chloride concentration profiles. Published in 2007 by John Wiley & Sons, Ltd.  相似文献   

东昆仑造山带东段哈图沟–清水泉–沟里韧性剪切带塑性变形及动力学条件研究   总被引：1，自引：0，他引：1  

李小兵  裴先治  陈有炘  刘成军  李佐臣  李瑞保  陈国超  魏博 《大地构造与成矿学》2015,(2)

东昆仑造山带东段哈图沟–清水泉–沟里韧性剪切带记录了多个旋回的造山作用,本文通过对韧性剪切带中石英c轴组构和显微构造特征测试分析,探讨东昆仑造山带东段陆块间俯冲拼合及地壳伸展减薄的形成机制。结果显示,韧性剪切带变形温度介于380~650℃之间,形成环境为中–高绿片岩相到低角闪岩相,剪切带内差异应力值介于173~509 MPa之间,应变速率介于6.93×10–14~1.43×10–8 s–1之间,主体为10–11~10–10 s–1,显示韧性剪切带变形是快速俯冲作用下的产物,越靠近东昆仑造山带东段东昆中断裂带其变形温度、差异应力值及相应的应变速率值越大,表明东昆仑造山带东段韧性剪切变形中心为东昆中断裂带。利用不同方法所计算出的韧性剪切带运动学涡度值,显示韧性剪切带早期瞬时运动学涡度(0.56~1)对应于东昆仑造山带东段东昆南与东昆仑造山带东段东昆北陆块间俯冲的初始阶段,中后期运动学涡度(0.25~0.91)应当对应于东昆南与东昆北陆块间的俯冲碰撞阶段,最晚期的C′瞬时运动学涡度(0.19~0.51)则对应于后造山的伸展阶段。通过石英c轴组构结合其宏微观构造特征,认为东昆中构造带至少经历了3个期次的构造运动,分别为加里东晚期的逆冲兼左行走滑剪切作用、晚海西–印支期的逆冲兼右行走滑剪切作用和燕山早期及之后的脆韧性–脆性的左行走滑剪切作用。  相似文献   

Geostrophic Adjustment Problems in a Polar Basin     

Maria V. Luneva  Andrew J. Willmott  Miguel Angel Morales Maqueda 《大气与海洋》2013,51(2):134-155

The geostrophic adjustment of a homogeneous fluid in a circular basin with idealized topography is addressed using a numerical ocean circulation model and analytical process models. When the basin is rotating uniformly, the adjustment takes place via excitation of boundary propagating waves and when topography is present, via topographic Rossby waves. In the numerically derived solution, the waves are damped because of bottom friction, and a quasi-steady geostrophically balanced state emerges that subsequently spins-down on a long time scale. On the f-plane, numerical quasi-steady state solutions are attained well before the system's mechanical energy is entirely dissipated by friction. It is demonstrated that the adjusted states emerging in a circular basin with a step escarpment or a top hat ridge, centred on a line of symmetry, are equivalent to that in a uniform depth semicircular basin, for a given initial condition. These quasi-steady solutions agree well with linear analytical solutions for the latter case in the inviscid limit.

On the polar plane, the high latitude equivalent to the β-plane, no quasi-steady adjusted state emerges from the adjustment process. At intermediate time scales, after the fast Poincaré and Kelvin waves are damped by friction, the solutions take the form of steady-state adjusted solutions on the f-plane. At longer time scales, planetary waves control the flow evolution. An interesting property of planetary waves on a polar plane is a nearly zero eastward group velocity for the waves with a radial mode higher than two and the resulting formation of eddy-like small-scale barotropic structures that remain trapped near the western side of topographic features.

RÉSUMÉ?Traduit par la rédaction] Nous étudions l'ajustement géostrophique d'un fluide homogène dans un bassin circulaire ayant une topographie idéalisée à l'aide d'un modèle numérique de circulation océanique et de modèles analytiques de processus. Quand le bassin est en rotation uniforme, l'ajustement se fait par l'excitation d'ondes de propagation aux limites, et en présence de topographie, par des ondes de Rossby topographiques. Dans la solution numériquement dérivée, les ondes sont amorties à cause frottement contre le fond, et un état quasi-stable géostrophiquement équilibré s’établit pour ensuite décélérer sur une longue période de temps. Sur le plan f, les solutions numériques d’états quasi-stables sont atteintes bien avant que l’énergie du système mécanique soit entièrement dissipée par le frottement. Nous démontrons que les états ajustés apparaissant dans un bassin circulaire avec un accore en forme de marche ou une crête en forme de merlon, centrés sur une ligne de symétrie, sont équivalents à ceux d'un bassin semi-circulaire de profondeur uniforme pour une condition initiale donnée. Les solutions quasi-stables s'accordent bien avec les solutions analytiques linéaires pour le dernier cas dans la limite de la non-viscosité.

Sur le plan polaire, la haute latitude équivalente au plan β, le processus d'ajustement n'aboutit à aucun état ajusté quasi-stable. Aux échelles de temps intermédiaires, après l'amortissement des ondes rapides de Poincaré et Kelvin par le frottement, les solutions prennent la forme de solutions ajustées d’états stables sur le plan f. Aux échelles de temps plus longues, les ondes planétaires déterminent l’évolution de l’écoulement. Une propriété intéressante des ondes planétaires sur un plan polaire est une vitesse de groupe presque nulle vers l'est pour les ondes ayant un mode radial plus grand que deux et la formation résultante de structures barotropiques de petite échelle de type remous qui demeurent emprisonnées près du bord ouest des caractéristiques topographiques.  相似文献   

不同环境风场条件下两次华南西部低涡暴雨个例对比分析   总被引：1，自引：0，他引：1  

高安宁  赖珍权  张瑞波  陈见  陈伟斌 《气象》2013,39(1):11-19

利用常规观测资料、FY 2C卫星TBB资料、自动站降水量以及NCEP/NCAR再分析资料,对2009年7月3-4日(简称“09.7”)和2008年6月1 6 1 7日(简称“08.6”)两次发生在华南西部的低涡暴雨过程进行对比分析,结果表明:(1)低涡是两次暴雨过程的直接影响系统,“09.7”过程伴随西南低空急流,“08.6”过程无低空急流配合,中尺度辐合可能在两次强降水过程中有着直接的触发作用.(2)“09.7”过程的低层辐合强度及上升运动强度明显强于“08.6”过程.“09.7”过程较“08.6”过程,暖平流强度明显偏强,等温度平流线也较密集.(3)相比“08.6”过程,“09.7”过程水汽净流量更大,这是西南低空急流将充足水汽往暴雨区输送的结果.(4)“09.7”和“08.6”两次暴雨过程均与高空西风急流南侧的垂直环流圈密切相关,“09.7”过程由于低空有急流存在,上升运动维持时间长,降水强度大,历时长,“08.6”过程广西境内低空无急流,上升运动维持时间短,降水强度偏弱,历时短.  相似文献   

影响北京的一例沙尘天气过程的起沙沉降及输送路径分析   总被引：5，自引：1，他引：4  

张亚妮  张碧辉  宗志平  吴英 《气象》2013,39(7):911-922

本文选取2012年4月27-28日影响北京的一次沙尘天气过程进行分析,发现在本次过程中,沙源地区的沙尘暴主要发生在地面冷锋和500 hPa槽后,在近地层强烈的感热加热与中低层冷平流的共同作用下,形成了不稳定层结及深厚的混合层,最高可达600 hPa,是沙尘天气能够影响下游地区的重要条件。本文还通过分析等熵混合层厚度变化及其平流过程来追踪沙尘天气的输送路径和定位沉降地,发现本次过程有两种传输路径,一种是沿辽宁北部向东而后转向东北方向,主要沿等熵混合层平流向下游移动,之后随着等熵混合层的接地沉降到近地层,该路径影响高度较高;另一种是沿辽宁南部向东南方向移动,混合层平流较清楚,但沉降时与东北路径明显不同,在辽东半岛东部地面辐散气流及下沉运动的作用下发生沉降,并随冷锋后冷高压南侧的东风回流向西输送影响北京地区。另外,由于混合层之上的稳定层明显下压,使沙尘输送高度偏低。运用HYSPLIT模式模拟的前、后向轨迹证实了上述两种输送路径,表明北京的扬沙天气是由东风回流造成的。  相似文献   

雷达回波外推预报的误差分析   总被引：4，自引：0，他引：4  

王改利  赵翠光  刘黎平  王红艳 《高原气象》2013,32(3)

基于天气雷达资料的外推预报是灾害天气临近预报的基础,选取4次强降水过程分析了外推预报的误差.主要分析方法包括3个步骤:(1)采用多尺度回波跟踪方法确定雷达回波的运动场;(2)采用半拉格朗日平流方案对雷达回波进行外推;(3)预报结果和观测结果进行对比.利用去相关时间方法分析了雷达回波的可预报性,利用预报技巧评分和相对绝对误差对外推预报的误差进行了定量分析.此外,还分析了外推预报的误差与尺度之间的关系,以及外推预报中的不确定因素 回波强度变化和回波运动场变化在预报误差中的相对重要性.这4次强降水过程的误差分析表明,预报误差随预报时效的变化基本上是以指数规律递减的,大尺度的降水系统对应较长的持续性,对于发展演变较快、尺度较小的风暴,其持续性较短.  相似文献   

北疆暴雪过程的湿位涡诊断     

李如琦  唐冶  路光辉  赵克明  牟欢  陈斌 《沙漠与绿洲气象(新疆气象)》2013,7(5):1-6

利用NCEP1°×1°再分析资料,对2009年3月19—20日北疆沿天山一带一次暴雪天气过程进行诊断分析,着重探讨了湿位涡诊断在新疆暴雪预报中的应用。分析表明：暴雪的水汽输送有3个源地,低层负散度、向北倾斜的涡度“上负下正”分布、等θe线的陡立密集带、垂直速度负值区与暴雪落区均有较好的对应关系。暴雪主要发生在MPV1〉0、MPV2绝对值迅速增加且等值线密集分布的区域。MPV1下传增大,大气对流不稳定能量释放,低层MPV2绝对值增大,大气湿斜压性增强,下滑倾斜涡度增长是暴雪形成的重要原因。  相似文献