Possible Sources of Forecast Errors Generated by the Global/Regional Assimilation and Prediction System for Landfalling Tropical Cyclones. Part II: Model Uncertainty
Possible Sources of Forecast Errors Generated by the Global/Regional Assimilation and Prediction System for Landfalling Tropical Cyclones. Part II: Model Uncertainty
复制标题
DOI：
10.1007/s00376-018-7095-9
复制
发表时间：
2018-08
影响因子：
5.8
通讯作者：
Feifan Zhou;W. Duan;He Zhang;M. Yamaguchi
中科院分区：
文献类型：
--
作者：
Feifan Zhou;W. Duan;He Zhang;M. Yamaguchi
本文分析了全球/区域同化预报系统（GRAPES）对热带气旋路径预报的误差来源。在第一部分中，它表明，模式误差的GRAPES可能是登陆TC的预报差的主要原因。因此，对模型误差的进一步研究是第二部分的重点。将模型误差视为一种强迫，模型误差可以用好的预测和坏的预测的组合来表示。结果表明，存在系统模型误差。位势高度分量的模式误差具有周期性特征，周期为24 h，在60°S ~ 60°N范围内，自西向东呈2波数的全球型。这种周期性模式误差与大气半日潮的特征相似，反映了热带非绝热加热的信号，表明与热带非绝热加热有关的参数误差可能是周期性模式误差的来源。从预报方程中减去上述模型误差，就可以作出一系列新的预报。修正后的GRAPES模型的平均预报能力比单纯改进GRAPES模型的初始条件得到了提高。这证实了周期性模式误差对登陆TC路径预报的强烈影响。此外，若用以校正模型的模型误差是从额外的TC的检验中获得，则相应的校正模型的预测能力将得到改善。
This paper investigates the possible sources of errors associated with tropical cyclone (TC) tracks forecasted using the Global/Regional Assimilation and Prediction System (GRAPES). In Part I, it is shown that the model error of GRAPES may be the main cause of poor forecasts of landfalling TCs. Thus, a further examination of the model error is the focus of Part II. Considering model error as a type of forcing, the model error can be represented by the combination of good forecasts and bad forecasts. Results show that there are systematic model errors. The model error of the geopotential height component has periodic features, with a period of 24 h and a global pattern of wavenumber 2 from west to east located between 60°S and 60°N. This periodic model error presents similar features as the atmospheric semidiurnal tide, which reflect signals from tropical diabatic heating, indicating that the parameter errors related to the tropical diabatic heating may be the source of the periodic model error. The above model errors are subtracted from the forecast equation and a series of new forecasts are made. The average forecasting capability using the rectified model is improved compared to simply improving the initial conditions of the original GRAPES model. This confirms the strong impact of the periodic model error on landfalling TC track forecasts. Besides, if the model error used to rectify the model is obtained from an examination of additional TCs, the forecasting capabilities of the corresponding rectified model will be improved.