Can CINRAD Radar With VCP-21 Mode Capture the Accumulated Rainfall Pattern and Intensity of Fast-Moving Storms?

China New Generation Weather Radar (CINRAD) operated in volume coverage pattern 21 (VCP21) mode may miss important information about precipitation for storms that evolve rapidly and move fast due to its volume scanning interval (about 6 min). However, despite the rapid changes and fast movement of storms, according to the continuity equation, the pattern and location of storms are continuous in temporal and spatial. An attempt is made in this research to use interpolation to supplement the missing information about storm evolution and improve the radar quantitative precipitation estimation (QPE) quality. Three interpolation methods are used to supplement storm evolution information between scan intervals for two fast-moving storm events. In these events, weather radar using VCP-21 mode cannot capture storm evolution well. The results show that all of the three interpolation methods do enhance the accuracy of the radar QPE. However, the linear interpolation method only describes the linear variation of storms, and the optical flow method can consider the movement of the storm and has a significant improvement in capturing the rainfall area, yet it cannot delineate the variation in rainfall shape and intensity. The Bi-directional optical flow (BIO) can describe not only the storm movement, but also the change of intensity and pattern of storms. BIO can greatly enhance the accuracy of radar QPE among the three methods. This study suggests that the interpolation of fast-moving storms between two neighboring radar volume scans needs to take into account both intensity variation and precipitation movement. The application of the BIO method can significantly improve the accuracy of radar QPE, namely the rainfall intensity and pattern.