【作者】 何芬；

【导师】 马镜娴； 沈桐立；

【作者基本信息】 南京信息工程大学 ， 气象学， 2005， 硕士

【摘要】 四维伴随变分同化方法作为一种提高数值天气预报的有效方法受到了很多国内外专家的关注。本文详细地介绍了构造伴随模式的基本方法-伴随码技术以及伴随模式中权重、尺度因子、下降算法的选取,接着介绍了以变分法为基础,以伴随码技术为核心的MM5伴随模式同化系统。以2002年7月23日的天气过程为例,将常规资料和非常规云导风资料应用于MM5伴随模式同化系统,进行了修正模式地形参数的试验研究。通过对不同初始地形的修正试验表明, MM5伴随模式同化系统能够对地形误差进行修正,并得到与资料更为协调一致的地形。另外,利用非常规云导风资料能够比仅使用常规资料更有效地修正模式地形参数。风场敏感性试验表明,在进行数值模拟时,针对不同模拟区域的地貌,适当增加某层风场的权重,可以更有效地调整模式地形,使修正后的地形与资料更协调。最后,将修正后的地形场作为模式地形进行数值模拟,发现用修正后的地形特别是经云导风资料修正后的地形作为模式地形所得的预报结果比使用未经修正的地形作为模式地形有所改善。同时,将集合预报的思想用于地形调整,结果发现,将集合平均的地形作为模式地形,可以在预报中得到一个比较稳定的预报结果,避免单一个例预报的偶然性。这为伴随模式同化系统的更广泛应用提供了一种新的思路。更多还原

【Abstract】 As an efficient approach to improve the accuracy of numerical weather prediction (NWP), Four-dimensional Adjoint Variational Assimilation is focused on by many national meteorologists. In this paper the technique of adjoint codes which is a basic means of constructing adjoint model and the selection of weight, scaling and descend arithmetic are introduced amply. Then the MM5 Adjoint-model Assimilation System that is based on variational method with adjoint codes technique is introduced. Model terrain adjustment is carried out by means of the MM5 adjoint-model assimilation system (AMAS) using the conventional observation data and non-conventional data cloud-derived winds. Two different initially-estimated terrains (from stochastic intensification and weakening) are given and corrected by use of the AMAS, which indicates much the same assimilation for the terrains differing from each other. The modified terrains are more consistent with the observation data. For the terrain parameter of identical errors, the adjoint model with inclusion of non-conventional cloud-derived winds in will improve even more the AMAS modification to the terrain parameter. As shown in the subsequent sensitivity runs, an increase in the proportion of a certain level wind in different regions will adjust the terrains in effect. To verify effects of modified terrain on NWP, experiment is conducted on a large-scale rainstorm over the Changjiang-Huai basin on 23-24 July, 2002, indicating that the terrain modified by conventional data and especially the one adjusted by cloud-derived winds used as the MM5 surface feature will improve prediction than the unmodified terrain. At the same time, Ensemble Prediction technique is used in terrains modification. It was found that a stable prediction can be gotten and the chanciness of a single case can be avoided after the ensemble averaging terrain is used. A new feasible approach about the widely application of AMAS is offered in this paper.更多还原