Operational Application of Optical Flow Techniques to Radar-Based Rainfall Nowcasting

Hong Kong Observatory has been operating an in-house developed rainfall nowcasting system called “Short-range Warning of Intense Rainstorms in Localized Systems (SWIRLS)” to support rainstorm warning and rainfall nowcasting services. A crucial step in rainfall nowcasting is the tracking of radar ech...

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Bibliographic Details
Published in:Atmosphere 2017, Vol.8 (3), p.48
Main Authors: Woo, Wang-chun, Wong, Wai-kin
Format: Article
Language:English
Subjects:
Algorithms
Computation
Computer terminals
Echoes
Genetic transformation
Mathematical models
Methods
motion tracking
nowcast
Nowcasting
optical flow
Optical flow (image analysis)
Pedestrians
Radar
Radar clutter
Radar echoes
Radar tracking
Rain
Rainfall
Rainfall applications in nowcasting
Rainstorms
Reflectance
Storm warning services
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Summary:Hong Kong Observatory has been operating an in-house developed rainfall nowcasting system called “Short-range Warning of Intense Rainstorms in Localized Systems (SWIRLS)” to support rainstorm warning and rainfall nowcasting services. A crucial step in rainfall nowcasting is the tracking of radar echoes to generate motion fields for extrapolation of rainfall areas in the following few hours. SWIRLS adopted a correlation-based method in its first operational version in 1999, which was subsequently replaced by optical flow algorithm in 2010 and further enhanced in 2013. The latest optical flow algorithm employs a transformation function to enhance a selected range of reflectivity for feature tracking. It also adopts variational optical flow computation that takes advantage of the Horn–Schunck approach and the Lucas–Kanade method. This paper details the three radar echo tracking algorithms, examines their performances in several significant rainstorm cases and summaries verification results of multi-year performances. The limitations of the current approach are discussed. Developments underway along with future research areas are also presented.
ISSN:2073-4433
2073-4433
DOI:10.3390/atmos8030048