Three-dimensional precipitation nowcasting with rapid and dense phased array weather radar observations

The phased array weather radar (PAWR) is a cutting-edge weather radar that can make rapid and dense observations. In Japan, a PAWR that can observe the whole sky every 30 seconds within a 60-km range at about 100 elevation angles has been developed.

Taking advantage of the unique, rapid and dense observations by PAWR, we developed a short-term precipitation nowcasting system based on the 3-dimensional (3D) tracking algorithm. Experiments were performed at 1—10 km scales up to several minutes to capture a rapid development of local convective rainfall. Conventional nowcasting approaches are based on 2D five-minute-scan radar data and predict motions of precipitation areas at O(100)-km-scales up to 1—6 hours. In this study, a 3D precipitation extrapolation system is developed based on the COTREC algorithm and tested using both simulated and real PAWR data. The 3D extrapolation system successfully captured 3D motion of precipitation cores and outperformed 2D nowcasting. We will seek for further improvements of the 3D extrapolation algorithm by applying an idea of data assimilation and accumulating information from multiple time steps.