Impact of Instantaneous Parameter Sensitivity on Ensemble-Based Parameter Estimation: Simulation with an Intermediate Coupled Model

On ensemble-based coupled data assimilation, cross-component parameter estimation, has not been as extensively developed and applied as weakly coupled state and parameter estimation along with cross-component state estimation. This discrepancy is partially attributed to the lack of emphasis on the instantaneous response of coupled model states with respect to parameters across different components. We define so-called response as the instantaneous parameter sensitivity (IPS). Under the framework of sequential assimilation, the prior information heavily relies on the IPS of coupled states with different time scales. Based on the IPS analysis for an intermediate coupled model, a series of twin experiments of state and parameter estimation are conducted.针对基于集合的耦合数据同化（ensemble-based coupled data assimilation）中的跨分量参数估计（cross-component parameter estimation），其发展与应用的广泛程度远不及弱耦合状态与参数估计（weakly coupled state and parameter estimation）以及跨分量状态估计（cross-component state estimation）。该差异部分源于学界对不同分量间耦合模式状态相对于参数的瞬时响应（instantaneous response）缺乏足够重视。我们将该瞬时响应定义为瞬时参数敏感性（Instantaneous Parameter Sensitivity, IPS）。在顺序同化（sequential assimilation）框架下，先验信息（prior information）在很大程度上依赖于不同时间尺度下耦合状态的瞬时参数敏感性。基于对某一中间耦合模式（intermediate coupled model）的瞬时参数敏感性分析，我们开展了一系列状态与参数估计的孪生试验（twin experiments）。