排序方式: 共有16条查询结果,搜索用时 31 毫秒
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经典四维变分同化(four dimensional variational data assimilation,简称4dvar)中认为模式是完美的, 而实际数值模式中存在的模式误差将对变分同化效果产生直接影响, 弱约束4dvar的提出为4dvar中考虑模式误差的影响提供了一种可行途径. 研究了基于模式误差控制变量的弱约束4dvar基本理论, 并在一维浅水方程组中对其同化效果及估计模式误差的有效性进行相关数值实验研究. 结果表明,在模式误差不可忽略的情况下,模式误差弱约束4dvar在整个区间 (包括同化区间和预报区间)上预报误差均比传统4dvar小, 在模式误差相对较大时改进效果更明显,具有明显优越性; 并且,模式误差弱约束4dvar能有效估计模式误差大小及分布形式. 相似文献
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Application of Tikhonov regularization method to wind retrieval from scatterometer data Ⅱ: cyclone wind retrieval with consideration of rain 下载免费PDF全文
According to the conclusion of the simulation experiments in paper I, the Tikhonov regularization method is applied to cyclone wind retrieval with a rain-effect-considering geophysical model function (called GMF+Rain). The GMF+Rain model which is based on the NASA scatterometer-2 (NSCAT2) GMF is presented to compensate for the effects of rain on cyclone wind retrieval. With the multiple solution scheme (MSS), the noise of wind retrieval is effectively suppressed, but the influence of the background increases. It will cause a large wind direction error in ambiguity removal when the background error is large. However, this can be mitigated by the new ambiguity removal method of Tikhonov regularization as proved in the simulation experiments. A case study on an extratropical cyclone of hurricane observed with SeaWinds at 25-km resolution shows that the retrieved wind speed for areas with rain is in better agreement with that derived from the best track analysis for the GMF+Rain model, but the wind direction obtained with the two-dimensional variational (2DVAR) ambiguity removal is incorrect. The new method of Tikhonov regularization effectively improves the performance of wind direction ambiguity removal through choosing appropriate regularization parameters and the retrieved wind speed is almost the same as that obtained from the 2DVAR. 相似文献
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文章首先利用QuikSCAT散射计获取的海面风场资料,利用华盛顿大学行星边界层(UWPBL)模式对台风海平面气压场进行反演(称为直接反演),并对其强度进行了分析;然后对获取的海面风场,采用变分方法对风场进行分解,分解出无旋和有旋风场,对分解出的有旋风场,再利用UWPBL模式对魔羯台风的海平面气压场进行了反演,对所得结果与通常直接反演、NCEP海平面气压场及台风报文资料进行一一对比,结果表明:新的反演定位的方法对台风海平面气压场中心气压的定位精度有了进一步的提高,此种定位的方法为散射计资料在台风中的实际应用开辟了一条新的思路.
关键词:
散射计风场
变分方法
台风
海平面气压场 相似文献
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The generalized variational data assimilation for non-differential dynamical systems is studied. There is no tangent linear model for non-differential systems and thus the general adjoint model can not be derived in the traditional way. The weak form of the original system was introduced, and then the generalized adjoint model was derived. The generalized variational data assimilation methods were developed for non-differential low dimensional system and non-differential high dimensional system with global and local observations. Furthermore, ideas in inverse problems are introduced to 4DVAR ( Fourdimensional variational ) of non-differential partial differential system with local observations. 相似文献
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通过引入信息容量的概念,并借助Bayesian估计理论,给出了星载探测资料中所包含的如温度,湿度,O3,SO2,CH4等大气参数的信息容量的计算方案,该方法充分考虑了仪器各通道对反演参数的敏感性、各通道的观测误差特性以及背景场的误差特性;然后利用该方法对HIRS,AMSU,AIRS,IAIS四种仪器以及三种组合所包含的大气温度、湿度的信息容量进行了计算,得到十分有价值的结果,该方法预期在星载大气探测仪器的设计、各仪器的评估与比较、探测资料的
关键词:
大气探测资料
信息容量
权函数矩阵 相似文献
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集合变分数据同化方法的同化效果对集合样本容量具有很强的依赖性,研究发现此问题的出现是因为其计算过程中分析增量被表示为集合扰动向量或其展开正交基向量的线性组合.这样的处理方法虽然避免了计算梯度而引入伴随模式,但是因为物理控制变量个数远大于集合样本容量,就会导致物理量的同化分析值对集合样本容量很敏感.根据此原因,提出了区域逐步分析方法,减小了同化分析区域内物理变量个数与集合样本容量数之间的比值,使问题得到解决.利用浅水方程模式进行资料同化数值试验表明,基于区域逐步分析的集合变分资料同化方法可以得到较好的结果,能明显提高同化的精度. 相似文献