分析约束的集合预报初始扰动构造方案的研究

集合预报初始扰动准确描述大气运动的不确定性是集合预报研究的核心问题，合理的扰动结构及振幅应能更好地反映大气运动状态的预报误差特征。随着集合扰动和资料同化的深入研究和理解，集合初始扰动方案与集合同化紧密结合协同发展。本文基于中国气象局数值预报中心自主研发的GRAPES-REPS集合预报系统，针对其初始扰动的结构和振幅与预报误差一致性较差的不合理问题，结合不同空间尺度天气系统预报误差特征，将表征预报不确定性的集合扰动与表达观测和预报不确定性的资料同化分析增量有效结合，研究提出了一种改善集合初始扰动质量的分析约束方案，以实现对集合初始扰动质量进一步改善。分析约束方案充分考虑资料同化分析增量的空间结构和量值特征，分别构造了单一定常和具有一定适应能力的两种分析约束函数，实现对初始扰动中不合理信息的识别和约束调整。试验结果表明，具有适应能力的分析约束方案对集合初始扰动具有良好的调整能力，约束后集合扰动的结构和振幅与中小尺度天气系统的预报误差更为吻合，其集合离散度和扰动能量的空间结构与演变特征更加趋于合理。分析约束方案可有效改善集合初始扰动质量及其预报性能。

Analysis Constraints Scheme of Initial Perturbation of Ensemble Prediction

The fundamental issue of ensemble forecasting research is whether initial perturbation can accurately describe the uncertainty of atmospheric motion. A reasonable structure and amplitude of ensemble perturbation should reflect the characteristics of forecast error about the state of atmospheric motion. For solving the problems of insufficient spread, recognizability, and reliability of perturbation in GRAPES regional ensemble forecast, this paper designs and develops different schemes to constrain the initial ensemble perturbation with analysis increments extracted from data assimilation system using the relationship of structure and evolution characteristics between the ensemble perturbation and forecast errors of weather systems at different scales. Further, this study analyzes the spatial, physical structure and spatiotemporal evolution characteristics of the ensemble perturbation, spread, and perturbation energy to comprehensively assess the quality and performance of the analysis constraints schemes. Results show that the schemes can partly identify and adjust the false perturbation in the original forecast. After constraining, the structure and evolution of the perturbation are in better agreement with the development of weather systems at different scales, with higher accuracy to describe the forecasting uncertainty. The structures of spreads and perturbation energy are more reasonable,and their growth characteristics over time are also more significant, particularly in the early period.