Coupling Ensemble Kalman Filter with Four-dimensional Variational Data Assimilation   总被引：2，自引：1，他引：1  

Fuqing ZHANG  Meng ZHANG  James A. HANSEN 《大气科学进展》2009,26(1):1-8

This study examines the performance of coupling the deterministic four-dimensional variational assimilation system (4DVAR) with an ensemble Kalman filter (EnKF) to produce a superior hybrid approach for data assimilation. The coupled assimilation scheme (E4DVAR) benefits from using the state-dependent uncertainty provided by EnKF while taking advantage of 4DVAR in preventing filter divergence: the 4DVAR analysis produces posterior maximum likelihood solutions through minimization of a cost function about which the ensemble perturbations are transformed, and the resulting ensemble analysis can be propagated forward both for the next assimilation cycle and as a basis for ensemble forecasting. The feasibility and effectiveness of this coupled approach are demonstrated in an idealized model with simulated observations. It is found that the E4DVAR is capable of outperforming both 4DVAR and the EnKF under both perfect- and imperfect-model scenarios. The performance of the coupled scheme is also less sensitive to either the ensemble size or the assimilation window length than those for standard EnKF or 4DVAR implementations.  相似文献   

基于卷积反投影CT重建的一种新型实用滤波函数   总被引：2，自引：0，他引：2  

杨民  路宏年  傅健 《CT理论与应用研究》2000,9(Z1):29-32

在实际的CT重建中,由于受散射、射束硬化等低频干扰因素的影响,使得重建图像产生"杯状”伪像以及图像模糊降质.针对在ICT工程实践中投影数据存在诸如此类的低频污染问题,本文提出了一新型实用滤波函数取代传统的滤波函数,得到了较为满意的重建效果.  相似文献   

An explicit four-dimensional variational data assimilation method   总被引：2，自引：0，他引：2  

Qiu ChongJian  Zhang Lei  Shao AiMei 《中国科学D辑(英文版)》2007,50(8):1232-1240

A new data assimilation method called the explicit four-dimensional variational (4DVAR) method is proposed. In this method, the singular value decomposition (SVD) is used to construct the orthogonal basis vectors from a forecast ensemble in a 4D space. The basis vectors represent not only the spatial structure of the analysis variables but also the temporal evolution. After the analysis variables are ex-pressed by a truncated expansion of the basis vectors in the 4D space, the control variables in the cost function appear explicitly, so that the adjoint model, which is used to derive the gradient of cost func-tion with respect to the control variables, is no longer needed. The new technique significantly simpli-fies the data assimilation process. The advantage of the proposed method is demonstrated by several experiments using a shallow water numerical model and the results are compared with those of the conventional 4DVAR. It is shown that when the observation points are very dense, the conventional 4DVAR is better than the proposed method. However, when the observation points are sparse, the proposed method performs better. The sensitivity of the proposed method with respect to errors in the observations and the numerical model is lower than that of the conventional method.  相似文献   

几种台风初始化方法及其对比实验     

王益柏  费建芳  张根生 《气象》2006,32(2):3-8

利用中尺度MM5V3模式及其伴随系统，运用四维变分同化方法，将Bogus台风作为观测资料进而优化台风初始场，对0422号台风个例进行了数值模拟和试验，并与传统Bogus方法和Nudging方法进行比较。结果表明，经过BDA方案优化的台风初始场更加接近实际台风的结构，有效地提高了台风路径和强度预报的准确率。  相似文献   

“8.19”西北东部大到暴雨诊断分析和数值模拟   总被引：8，自引：1，他引：8  

李晓霞  寿绍文  张铁军  奚立宗  张新荣 《气象》2006,32(2):81-86

利用MICAPS系统T213资料、NCEP再分析资料及实况观测资料，对2004年8月19日发生在西北地区东部的暴雨天气过程的大尺度环流背景和物理量场进行分析发现：这次暴雨天气过程中西太平洋副热带高压有一次明显的西伸，是一次较典型的副高西北侧西南气流型暴雨。降水水汽主要来自南海和孟加拉湾，中低层的水汽输送十分充沛，并在甘肃河东和宁夏形成辐合。运用三重嵌套的中尺度数值预报模式MM5，对这次暴雨过程进行了两种方案的高分辨率数值模拟，结果表明，运用四维资料同化后的方案在形势和降水预报方面优于未进行资料同化的方案。  相似文献   

一种地面气温的空间插值方法及其误差分析   总被引：18，自引：0，他引：18  

刘宇  陈泮勤  张稳  胡非 《大气科学》2006,30(1):146-152

根据最近邻域法和反向距离法的基本原理,利用空间卷积算法,采用结合中国大陆气象站点位置的截断高斯滤波算子作为距离权重方程,给出一种适合中国陆地区域的地面气温插值方法,并以300多个地面站记录的气温为例,使用交叉验证法分析了给定插值方法的误差分布,结果表明该插值方法比其他插值方法所得误差较小,能够很好地用于气象站点气象观测记录缺失的插补及其空间尺度的扩大化.  相似文献   

可控震源平板—大地振动模型及参数研究     

徐爱军  康丽生 《中国煤田地质》2001,13(3):62-64

本文对可控震源平板－大地系统建立了质量－弹簧－阻尼器振动数学模型，并给出了各模型参数与大地粘弹性，惯性指标。通过给定不同的相对阻尼比值及系统谐振频率，相应进行了理论计算，得出了其对平板大地系统振动影响的结论。文中得出的一些结论，对实际生产具有参考意义。  相似文献   

含透射衰减的地震反射信号褶积模型在波阻抗反演中的应用     

苑春方  余钦范  王彦春  杨瑞召 《物探与化探》2002,26(6):454-456,460

研究了地震波在层状地质模型内透射衰减对地震反射信号振幅的影响,给出了含透射衰减的褶积模型,为基于模型的波阻抗反演提供了一种新的正演方法。采用含透射衰减的褶积模型做正演运算,能够校正地层透射对波阻抗反演结果的影响,尤其能够消除地层的屏蔽现象。实际的资料处理表明含透射衰减的褶积模型有较好的应用价值。  相似文献   

一类曲线图象重建卷积反投影算法     

吴一刚  邱佩璋 《CT理论与应用研究》1992,(4)

本文给出了一类平面曲线 s=4(x,y)·coxθ+B(x,y)·sinθ上的 Radon 变换卷积反投影算法,并进行了数值模拟,其重建结果与真实数据相吻合,其中 A(x,y)和 B(x,y)满足一定条件.  相似文献   

FOUR-DIMENSIONAL DATA QUALITY CONTROL THROUGH THE ADJOINT APPROACH^*     

Zhu Jiang 《Acta Meteorologica Sinica》1996,10(1):73-80

Using the variational four-dimensional (4-D) data assimilation technique (the adjoint method), we defined the error/mean-error ratios (EMER) of observational data. The plausibility of marking the gross error using the EMER is investigated theoretically under some assumptions.Idealized numerical experiments are carried out using the simple Lorenz model to test the quality control scheme.  相似文献