Journal of Meteorological Research

, Volume 31, Issue 4, pp 747–766 | Cite as

Improving the extreme rainfall forecast of Typhoon Morakot (2009) by assimilating radar data from Taiwan Island and mainland China

  • Xuwei Bao
  • Dan Wu
  • Xiaotu Lei
  • Leiming Ma
  • Dongliang Wang
  • Kun Zhao
  • Ben Jong-Dao Jou


This study examined the impact of an improved initial field through assimilating ground-based radar data from mainland China and Taiwan Island to simulate the long-lasting and extreme rainfall caused by Morakot (2009). The vortex location and the subsequent track analyzed through the radial velocity data assimilation (VDA) are generally consistent with the best track. The initial humidity within the radar detecting region and Morakot’s northward translation speed can be significantly improved by the radar reflectivity data assimilation (ZDA). As a result, the heavy rainfall on both sides of Taiwan Strait can be reproduced with the joint application of VDA and ZDA. Based on sensitivity experiments, it was found that, without ZDA, the simulated storm underwent an unrealistic inward contraction after 12-h integration, due to underestimation of humidity in the global reanalysis, leading to underestimation of rainfall amount and coverage. Without the vortex relocation via VDA, the moister (drier) initial field with (without) ZDA will produce a more southward (northward) track, so that the rainfall location on both sides of Taiwan Strait will be affected. It was further found that the improvement in the humidity field of Morakot is mainly due to assimilation of high-value reflectivity (strong convection) observed by the radars in Taiwan Island, especially at Kenting station. By analysis of parcel trajectories and calculation of water vapor flux divergence, it was also found that the improved typhoon circulation through assimilating radar data can draw more water vapor from the environment during the subsequent simulation, eventually contributing to the extreme rainfall on both sides of Taiwan Strait.

Key words

Morakot radar assimilation rainfall simulation 


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The authors are grateful to Dr. Fuqing Zhang and the two anonymous reviewers for providing valuable comments and suggestions that improved our original manuscript.


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Copyright information

© The Chinese Meteorological Society and Springer-Verlag GmbH Germany 2017

Authors and Affiliations

  • Xuwei Bao
    • 1
  • Dan Wu
    • 1
  • Xiaotu Lei
    • 1
  • Leiming Ma
    • 1
  • Dongliang Wang
    • 1
  • Kun Zhao
    • 2
  • Ben Jong-Dao Jou
    • 3
  1. 1.Shanghai Typhoon InstituteChina Meteorological AdministrationShanghaiChina
  2. 2.Key Laboratory of Mesoscale Severe Weather/Ministry of Education, and School of Atmospheric SciencesNanjing UniversityNanjingChina
  3. 3.Department of Atmospheric SciencesNational Taiwan UniversityTaipeiChina

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