共查询到20条相似文献，搜索用时 31 毫秒
1.
南海及周边海域风浪流耦合同化精细化数值预报与信息服务系统简介 总被引：1，自引：0，他引：1
面向社会需求,建立覆盖南海及周边海域的高分辨率风-浪-流耦合同化数值预报与信息服务系统。系统包含耦合同化数值预报模式、海洋动力环境数据库与可视化平台两部分。其中,耦合同化数值预报模式由中尺度大气数值预报模式、海浪数值预报模式和区域海洋环流数值模式,在C-Coupler耦合器中进行耦合,引入集合调整Kalman滤波同化模块,在耦合预报前进行大气、海浪和海流的同化后报模拟,为耦合预报模式提供更为精确的初始场。预报结果经海洋动力环境数据库和可视化平台处理后,通过二维和三维可视化展示,向用户提供直观的南海及周边海域海洋环境预报产品。 相似文献
2.
In this article, we present the latest version of an ensemble forecasting system of the hydrodynamics of the Black Sea, based on the GHER model. The system includes the Weakly Constrained Ensembles algorithm to generate random, but physically balanced perturbations to initialize members of the ensemble. On top of initial conditions, the ensemble accounts also for uncertainty on the atmospheric forcing fields, and on some scalar parameters such as river flows or model diffusion coefficients. The forecasting system also includes the Ocean Assimilation Kit, a sequential data assimilation package implementing the SEEK and Ensemble Kalman filters. A novel aspect of the forecasting system is that not only our best estimate of the future ocean state is provided, but also the associated error estimated from the ensemble of models. The primary goal of this paper is to quantitatively show that the ensemble variability is a good estimation of the model error, regardless of the magnitude of the forecast errors themselves. In order for this estimation to be meaningful, the model itself should also be well validated. Therefore, we describe the model validation against general circulation patterns. Some particular aspects critical for the Black Sea circulation are validated as well: the mixed layer depth and the shelfopen sea exchanges. The model forecasts are also compared with observed sea surface temperature, and errors are compared to those of another operational model as well. 相似文献
3.
JIAN SHENG 《地球，A辑:动力气象学与海洋学》2002,54(4):317-329
Based on results from a simple three-level quasi-geostrophic model, Lin and Derome suggested that atmospheric predictability is influenced by the Pacific/North American (PNA) pattern. In the present study, predictability experiments are conducted with the Canadian Centre for Climate Modelling and Analysis general circulation model (CCCma GCM). A 47-yr integration of the GCM with specified sea surface temperature (SST) for the years 1948–94 is first performed. Forecasts are initiated whenever the PNA pattern is in a strong positive or strong negative phase during this simulation. For each forecast, an ensemble of six initial conditions is generated with small random perturbations. Forecasts initiated when the PNA is in its positive phase have smaller growth rates of ensemble standard deviation than forecasts initiated when the PNA is in its negative phase. Regional characteristics of the prediction spread are also examined. Similar experiments are conducted to determine the relationship between atmospheric predictability and SST anomalies in the tropical Pacific. Forecasts initiated when tropical SST anomalies are positive have smaller growth rates of ensemble standard deviation than forecasts initiated when tropical SST anomalies are negative. However, cases with positive tropical SST anomalies but without a strong PNA pattern show a similar prediction spread to cases with negative SST anomalies. The results suggest that, in comparison to the PNA pattern, the influence of tropical SST anomalies is only secondary. A set of three-layer diagnostic equations is used to analyze the GCM results. It is speculated that the transient eddies have a stronger influence on the circulation anomalies (and therefore reduce the atmospheric predictability more) in the negative PNA phase than in the positive PNA phase. 相似文献
4.
为了改进温带气旋数值预报的精度,基于WRF(Weather Research and Forecasting)模式,利用GSI(Gridpoint Statistical Interpolation)-EnKF(Ensemble Kalman Filter)系统,设计了一套温带气旋集合预报方法,其具有的2种选择方案通过滤掉质量较差的集合成员从而将集合成员数目控制在10以内,达到了大幅降低集合预报计算量的目的。针对2020年7月一次影响黄海的温带气旋个例,开展了一系列决定性预报与集合预报的数值对比试验。分析结果如下:1)不采取任何择优方案的集合预报效果就已经明显优于决定性预报,而采取择优方案使得预报效果进一步得到提升;2)预报初始时刻择优(直接择优方案)的集合预报效果远不如短时积分3 h后才进行择优(积分择优方案)的预报效果; 3)积分择优方案优于直接择优方案的原因是,初始场集合体中的成员经过短时积分后其误差得以放大而使得择优更加准确。多个例的应用结果进一步表明,本文提出的积分择优方案温带气旋集合预报方法具有较好的业务预报应用前景。 相似文献
5.
中等海况下,星载合成孔径雷达(Synthetic Aperture Radar,SAR)已经广泛应用于海洋动力环境要素的监测(风场、波浪、流场)。近年来,SAR高海况遥感,尤其是探测台风海面风场、巨浪、流场已经成为国内外研究热点,并突破了一些关键技术。利用SAR多极化成像模式对海观测和新发展的地球物理模式函数,可以提取高海况下的海面风速、风向、有效波高、流速和流向等海洋表面关键物理参数。这些环境要素可以用于海洋灾害监测预警;为海洋和大气数值模式提供准确的初始场和同化源,改进模式预报精度;为研究全球气候变化提供有力的观测依据。 相似文献
6.
针对有效波高资料提出一种海浪谱分解与重构的资料同化方案:利用历史时段内的有效波高观测资料和模式计算波高场,采用最优插值方法得到分析波高场;在WAVEWATCH-Ⅲ模式的波浪能量密度谱和有效波高分析值之间引入一个变异系数矩阵,描述模式的误差,以此为状态向量构建卡尔曼滤波系统,对分解过的海浪谱进行修正和重构,得到同化后的海浪谱初始场。利用美国阿拉斯加湾北部海域的7个浮标站进行同化和72 h预报试验,对连续1个月的预报结果进行统计表明:采用该同化方案后24 h预报结果的有效波高均方根误差比未同化的结果降低了0.13 m;同化方案对预报效果的影响可持续36 h左右,随着预报时效延长,同化的效果减弱。 相似文献
7.
Sea surface temperature (SST) prediction based on the multi-model seasonal forecast with numerous ensemble members have more useful skills to estimate the possibility of climate events than individual models. Hence, we assessed SST predictability in the North Pacific (NP) from multi-model seasonal forecasts. We used 23 years of hindcast data from three seasonal forecasting systems in the Copernicus Climate Change Service to estimate the prediction skill based on temporal correlation. We evaluated the predictability of the SST from the ensemble members' width spread, and co-variability between the ensemble mean and observation. Our analysis revealed that areas with low prediction skills were related to either the large spread of ensemble members or the ensemble members not capturing the observation within their spread. The large spread of ensemble members reflected the high forecast uncertainty, as exemplified in the Kuroshio–Oyashio Extension region in July. The ensemble members not capturing the observation indicates the model bias; thus, there is room for improvements in model prediction. On the other hand, the high prediction skills of the multi-model were related to the small spread of ensemble members that captures the observation, as in the central NP in January. Such high predictability is linked to El Niño Southern Oscillation (ENSO) via teleconnection.
相似文献8.
For more and more applications in coastal and offshore engineering, numerical simulations of waves and surges are required. An important input parameter for such simulations are wind fields. They represent one of the major sources for uncertainties in wave and surge simulations. Wind fields for such simulations are frequently obtained from numerical hindcasts with regional atmospheric models (RAMs). The skill of these atmospheric hindcasts depends, among others, on the quality of the forcing at the boundaries. Furthermore, results may vary due to uncertainties in the initial conditions. By comparing different existing approaches for forcing a regional atmospheric model, it is shown that the models' sensitivity to uncertainties in the initial conditions may be reduced when a more sophisticated approach is used that has been suggested recently. For a specific, although somewhat brief test period, it is demonstrated that an improved hindcast skill for near surface wind fields is obtained when this approach is adopted. Consequences of the reduced uncertainty in wield fields for the hindcast skill of subsequent wave modelling studies are demonstrated. Recently, this new approach has been used together with a regional atmosphere model to produce a 40-year wind hindcast for the Northeast Atlantic, the North Sea and the Baltic Sea. The hindcast is presently extended to other areas and the wind fields are used to produce 40-year high-resolution hindcasts of waves and surges for various European coastal areas. 相似文献
9.
MASNUM-WAM海浪模式集合Kalman滤波同化研究-I.风场扰动对海浪模拟影响 总被引：1，自引：1，他引：0
模式集合样本的代表性和观测信息的可靠性是制约数据同化效果的重要因素,而前者对海浪模式同化的影响尤为显著。由于海浪模式对初始场的敏感性较弱,来自大气的风输入源函数是海浪的重要能量输入,如何合理地对风输入进行扰动,构造海浪的集合模式运行,是实现和改进海浪模式集合Kalman滤波同化的关键问题。为了实现海浪模式集合运行,本文提出了风场的三种集合扰动方案,分别为：纯随机数、随机场和时间滞后的风场扰动方法。本研究利用2014年1月ECMWF全球风场,基于这三种风场扰动方法开展了集合海浪模式的集合运行实验,并统计分析了海浪特征要素（有效波高）和二维波数谱对风场扰动的响应。结果表明,随机场集合扰动方案所构造的风场集合效果最佳,所得海浪模拟结果的集合样本发散度适中,能够较为合理地反映背景误差的统计特征,可用于进一步的集合Kalman滤波海浪数据同化实验。 相似文献
10.
为准确模拟台风路径和强度,采用WRF模式比较不同微物理过程和积云对流过程参数化方案对台风路径和强度模拟的影响,并基于集合预报方法考虑对台风预报系统误差进行优化。选用4种微物理过程方案和3种积云对流参数化方案,针对1213号台风“启德”进行模拟,结果表明不同的参数化方案对台风路径和强度的预报结果有明显影响,积云对流过程参数化方案相对于微物理过程参数化方案更加敏感。基于不同参数化方案扰动成员的集合平均预报方法,对于台风路径和强度的模拟误差均有明显改善,台风路径误差随时间增幅较小,其结果优于全部12个单方案试验的模拟结果;从台风强度方面来看,基于集合预报方法模拟得到的台风强度变化趋势与实况结果一致,且误差较小,优于大多数试验方案。结果表明:采用不同微物理过程和积云对流过程参数化方案的组合构建的集合预报模型,对于台风路径和强度的模拟均有一定程度改善,减小了采用不同参数化方案产生的路径不确定性,使其在台风“启德”的路径模拟上与实况更为接近,可为提升台风预报能力提供科学参考。 相似文献
11.
Estimation of near-field characteristics of tsunami generation by submarine landslide 总被引：3，自引：0，他引：3
Underwater landslide can trigger impulsive waves with high amplitude and run-up, which may cause substantial damage. In this work, the experimental investigations are performed to study the impulsive wave characteristics caused by underwater landslides. The effects of landslide geometry and kinematics on wave characteristics are studied by performing 84 laboratory experiments. The influences of thickness, volume and shape of failure mass on the characteristics of initial wave are discussed. The impacts of water body conditions such as the slope of sliding bed and the initial submergence of underwater landslide are also examined. The present experimental data as well as the available data in the literature are used to provide an applied method for prediction of the initial wave amplitude. The present prediction method is properly verified by several experimental, numerical and real case data. 相似文献
12.
A method of incorporating pressure forcing into a nonlinear potential flow wave model is presented. A semi-analytical pseudo-spectral method is used to calculate dynamic response of a water body exposed to evolving local pressure distribution. Surface slope coherent and slope proportional pressure functions are directly applied through a pressure term appearing in the dynamic free-surface boundary condition of a formulated initial boundary-value problem. First, a monochromatic pressure distribution is used to generate steady regular waves of permanent form. The pressure-induced wave motion exhibits stable harmonic structure for deepwater, transitional water and shallow water waves. In the next step, a more complex pressure system is used to initiate multi-component wave propagation. It is demonstrated that the proposed method provides well-posed initial conditions for studying various water wave scenarios within a framework of nonlinear potential flow solutions. 相似文献
13.
利用一个两层半的热带海洋模式,采用数值实验的方法研究了热带海洋对于初始海洋混合层深度异常和大气季节内时间尺度热力强迫激发产生的Ｒｏｓｓｂｙ波和Ｋｅｌｖｉｎ波。研究表明,初始海洋混合层深度异常和大气热力强迫,可以在两层半热带海洋模式中激发产生东向传播具有Ｋｅｌｖｉｎ波性质的波动和具有Ｒｏｓｓｂｙ波性质的波动。热力强迫激发产生海洋Ｒｏｓｓｂｙ波和Ｋｅｌｖｉｎ波所需时间长于初始海洋混合层深度异常和大气季节内动力强迫激发产生两波所需时间,与大气季节内动力强迫激发的Ｒｏｓｓｂｙ波相比,初始深度异常与大气热力强迫激发产生Ｒｏｓｓｂｙ波具有不同的热力性质。 相似文献
14.
传统的四维变分数据同化方法在同化观测资料的同时可以对数值模式参数进行优化,然而传统的四维变分方法需要针对不同的数值模式编写特有的伴随模式,因此算法的可移植性差,同时计算时耗费大量资源。本文提出了一种新的基于解析四维集合变分的参数优化方法,该方法以迭代搜索得到的模式参数为基准展开扰动并构建样本集合,由此显式地计算协方差矩阵,并得到代价函数极小值的解析解,从而避免了伴随模式的使用。基于Lorenz-63模型对该方法进行单参数和多参数数值试验和优化效果检验,并在不同的同化时间窗口长度和观测采样间隔情况下,采用传统四维变分方法与之进行对比,结果显示,新方法表现出与传统四维变分相同的优化性能,都能有效收敛到真值,而新方法不需要计算伴随模式,可移植性好。本文还测试了不同的集合成员个数和模式参数真值的情况下新方法的同化效果,结果表明,新方法对集合样本个数及模型参数真值不敏感,采用较少的集合样本即可完成数据同化。 相似文献
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利用全球中期预报模式T63L9,选取2004年6月4日至13日10d作为试验个例进行了集合预报试验,分析了不同集合成员个数对于预报结果的影响。结果表明,集合预报的技巧都明显高于单个控制预报。在集合成员较少时,随集合成员教的增加,集合预报的技巧提高明显,当集合成员数多于11个时,集合预报的效果提高缓慢。在中期预报时段内。集合成员数11为集合预报效果随集合成员教趋于饱和的临界值,如果继续增加成员数.预报效果提高较少,但计算量却大大的增加。本文只是单个试验个例的分析结果。为验证结论的普适性,还需要进行更多的试验。 相似文献
17.
选取2014年4月发生的一次黄海近岸海雾个例,利用WRF(Weather Research and Forecasting)模式开展了集合预报试验研究。依据每个集合成员初始场中海平面气压、2 m温度、2 m水汽混合比与2 m相对湿度(relative humidity, RH)4个变量的均方根误差(root mean square error, RMSE)与RMSE集合平均值的相对大小,以剔除高于者而保留低于者的原则,设计了4种不同的初始场集合体择优方案,实施了一系列数值预报试验,比较了不同择优方案的集合预报效果。研究结果表明:(1)蒙特卡罗方法所生成的集合体中存在不少海雾预报效果较差的成员,这会降低集合预报效果,因此初始场择优十分必要;(2)以RH作为择优变量的择优方案(记为RH-RMSE方案),集合预报效果明显优于其他3种方案;(3)对比不择优集合预报,采用RH-RMSE方案的择优集合预报效果不仅节省了50%左右的计算时间,并且公正预兆评分(equitable threat score,ETS)改进率高达36%左右。本研究提出的RH-RMSE方案具有业务化应用前景。 相似文献
18.
Flow-dependent versus flow-independent initial perturbations for ensemble prediction 总被引：1，自引：0，他引：1
Ensemble prediction relies on a faithful representation of initial uncertainties in a forecasting system. Early research on initial perturbation methods tested random perturbations by adding 'white noise' to the analysis. Here, an alternative kind of random perturbations is introduced by using the difference between two randomly chosen atmospheric states (i.e. analyses). It yields perturbations (random field, RF, perturbations) in approximate flow balance.
The RF method is compared with the operational singular vector based ensemble at European Centre for Medium Range Weather Forecasts (ECMWF) and the ensemble transform (ET) method. All three methods have been implemented on the ECMWF IFS-model with resolution T L 255L40. The properties of the different perturbation methods have been investigated both by comparing the dynamical properties and the quality of the ensembles in terms of different skill scores. The results show that the RF perturbations initially have the same dynamical properties as the natural variability of the atmosphere. After a day of integration, the perturbations from all three methods converge. The skill scores indicate a statistically significant advantage for the RF method for the first 2–3 d for the most of the evaluated parameters. For the medium range (3–8 d), the differences are very small. 相似文献
The RF method is compared with the operational singular vector based ensemble at European Centre for Medium Range Weather Forecasts (ECMWF) and the ensemble transform (ET) method. All three methods have been implemented on the ECMWF IFS-model with resolution T
19.
Using a mesoscale ensemble to predict forecast error and perform targeted observation 总被引：2，自引：0，他引：2
Using NCEP short range ensemble forecast（SREF） system,demonstrated two fundamental on-going evolutions in numerical weather prediction（NWP） are through ensemble methodology.One evolution is the shift from traditional single-value deterministic forecast to flow-dependent（not statistical） probabilistic forecast to address forecast uncertainty.Another is from a one-way observation-prediction system shifting to an interactive two-way observation-prediction system to increase predictability of a weather system.In the first part,how ensemble spread from NCEP SREF predicting ensemble-mean forecast error was evaluated over a period of about a month.The result shows that the current capability of predicting forecast error by the 21-member NCEP SREF has reached to a similar or even higher level than that of current state-of-the-art NWP models in predicting precipitation,e.g.,the spatial correlation between ensemble spread and absolute forecast error has reached 0.5 or higher at 87 h（3.5 d） lead time on average for some meteorological variables.This demonstrates that the current operational ensemble system has already had preliminary capability of predicting the forecast error with usable skill,which is a remarkable achievement as of today.Given the good spread-skill relation,the probability derived from the ensemble was also statistically reliable,which is the most important feature a useful probabilistic forecast should have.The second part of this research tested an ensemble-based interactive targeting（E-BIT） method.Unlike other mathematically-calculated objective approaches,this method is subjective or human interactive based on information from an ensemble of forecasts.A numerical simulation study was performed to eight real atmospheric cases with a 10-member,bred vector-based mesoscale ensemble using the NCEP regional spectral model（RSM,a sub-component of NCEP SREF） to prove the concept of this E-BIT method.The method seems to work most effective for basic atmospheric state variables,moderately effective for convective instabilities and least effective for precipitations.Precipitation is a complex result of many factors and,therefore,a more challenging field to be improved by targeted observation. 相似文献
20.
在黄海海雾的数值模拟中,EnKF（ensemble Kalman filter）是一种优于3DVAR（three-dimensional variational）的数据同化方法。研究发现,对EnKF初始场集合体采取常用的集合平均所产生的确定性预报初始场,会出现初始场中海雾在预报开始后就迅速消失以及接下来海雾难以生成的异常现象。通过详细的海雾个例研究,清晰地揭示并解释了此现象,指出这是集合平均造成初始场中云水与温度湿度之间存在不协调关系所导致的后果,并提出了一种择优加权平均方法来取代常用的集合平均。研究结果表明,海雾确定性预报采用择优加权平均所构建的初始场,可以消除上述异常现象,显著改进海雾模拟效果。 相似文献