| dc.description.abstract | Severe weather system accompanies with heavy rainfall is a common event which often occurs in summer time over Taiwan area. It affects people security, life safety, and the economy. Therefore, how to predict such kind of events and prevent the disasters is an major issue for the operational unit. In this study, the Storm Cell Identification and Tracking (SCIT) algorithm in the System for Convection Analysis and Nowcasting (SCAN), which is applied in the forecast center of Central Weather Bureau (CWB), is used to survey the occurrence of convective cells, identify their locations and track the movements for the nowcasting. To examine the convective cells statistically, a set of historical data between March and August from 2015 to 2018 are selected for this study. In addition, the RCWF (Wu-Fan San) radar data is collected to represent northern Taiwan area, and the RCCG (Chi-Gu) radar data is selected to represent southern Taiwan area.
Results of the analysis show that, most of convective cells have about 1-hour life time. In addition, the distribution of cells shows more convection events over the ocean area in northern Taiwan compared with southern Taiwan, but the cell density over land area is higher than ocean area in both location.
To improve the nowcasting quantitatively, the tracking error of the convective cells are estimated in statistics. Based on the moving speed of the cells, the Potential Track Area algorithm is applied in 4 categories to define the affected radius of convective cells in the period of 0-1h nowcasting. By examining the performance of storm tracking in 2019, result shows that the hit rate is about 60~70%. When further providing additional information of environment flow, the performance of nowcasting can be further improved in some cases. | en_US |