Assimilating AMSU-a radiance data with the WRF hybrid En3DVAR system for track predictions of Typhoon Megi (2010)
Assimilating AMSU-a radiance data with the WRF hybrid En3DVAR system for track predictions of Typhoon Megi (2010)
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DOI：
10.1007/s00376-014-4239-4
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发表时间：
2015-07
影响因子：
5.8
通讯作者：
Feifei Shen;J. Min
中科院分区：
文献类型：
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作者：
Feifei Shen;J. Min
利用天气研究与预报（WRF）模式和混合集合三维变分（En 3DVAR）资料同化（DA）系统，研究了AMSU-A同化辐射对台风“鲇鱼”（2010）路径预报的影响。研究了调整与静态背景误差协方差（BEC）相关的长度尺度因子和方差尺度因子对台风路径预报的影响。结果表明，在台风辐亮度资料同化中，适当的尺度因子可以提高台风路径的预报效果。AMSU-A辐射同化使用3DVAR轨道预报有轻微的积极影响，即使静态BEC仔细调整，以优化其性能。当混合DA被采用时，路径预报显着改善，特别是对穿越菲律宾后的急剧北转，与流量相关的集合协方差。与气流相关的BEC可以通过混合DA来估计，并且能够系统地调整台风的位置。通过比较分析增量和混合DA和3DVAR生成的预报，揭示了集合预报中台风特有的BEC的影响。此外，对于24小时的预测，混合DA实验与使用全流量依赖的背景误差大大优于3DVAR的水平风和温度在低层和对流层中，并在所有级别的水分。
The impact of assimilating radiances from the Advanced Microwave Sounding Unit-A (AMSU-A) on the track prediction of Typhoon Megi (2010) was studied using the Weather Research and Forecasting (WRF) model and a hybrid ensemble three-dimensional variational (En3DVAR) data assimilation (DA) system. The influences of tuning the length scale and variance scale factors related to the static background error covariance (BEC) on the track forecast of the typhoon were studied. The results show that, in typhoon radiance data assimilation, a moderate length scale factor improves the prediction of the typhoon track. The assimilation of AMSU-A radiances using 3DVAR had a slight positive impact on track forecasts, even when the static BEC was carefully tuned to optimize its performance. When the hybrid DA was employed, the track forecast was significantly improved, especially for the sharp northward turn after crossing the Philippines, with the flow-dependent ensemble covariance. The flow-dependent BEC can be estimated by the hybrid DA and was capable of adjusting the position of the typhoon systematically. The impacts of the typhoon-specific BEC derived from ensemble forecasts were revealed by comparing the analysis increments and forecasts generated by the hybrid DA and 3DVAR. Additionally, for 24 h forecasts, the hybrid DA experiment with use of the full flow-dependent background error substantially outperformed 3DVAR in terms of the horizontal winds and temperature in the lower and mid-troposphere and for moisture at all levels.