Abstract
This study developed a real-time rainfall forecasting system that can predict rainfall in a particular area a few hours before a typhoon’s arrival. The reflectivity of nine elevation angles obtained from the volume coverage pattern 21 Doppler radar scanning strategy and ground-weather data of a specific area were used for accurate rainfall prediction. During rainfall prediction and analysis, rainfall retrievals were first performed to select the optimal radar scanning elevation angle for rainfall prediction at the current time. Subsequently, forecasting models were established using a single reflectivity and all elevation angles (10 prediction submodels in total) to jointly predict real-time rainfall and determine the optimal predicted values. This study was conducted in southeastern Taiwan and included three onshore weather stations (Chenggong, Taitung, and Dawu) and one offshore weather station (Lanyu). Radar reflectivities were collected from Hualien weather surveillance radar. The data for a total of 14 typhoons that affected the study area in 2008–2017 were collected. The gated recurrent unit (GRU) neural network was used to establish the forecasting model, and extreme gradient boosting and multiple linear regression were used as the benchmarks. Typhoons Nepartak, Meranti, and Megi were selected for simulation. The results revealed that the input data set merged with weather-station data, and radar reflectivity at the optimal elevation angle yielded optimal results for short-term rainfall forecasting. Moreover, the GRU neural network can obtain accurate predictions 1, 3, and 6 h before typhoon occurrence.
Highlights
On the basis of the aforementioned problems, this study developed an hourly conceptual system for rainfall forecasting during typhoons based on radar reflectivity
This study developed a real-time rainfall forecasting system that can predict rainfall in an area a few hours before a typhoon arrives at Taiwan
To effectively predict rainfall data, this study used reflectivity data obtained from nine elevation angles in the Taiwan Doppler
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Taiwan is located in the intertropical convergence zone in the western Pacific Ocean with a geographical location of approximately 22◦ N–25◦ N and 120◦ E–122◦ E. Taiwan is frequently affected by typhoons during summer and autumn that result in heavy precipitation. Heavy precipitation causes disasters such as flooding, landslides, and debris flows, it is a main source of water [1,2]. When typhoons approach, government agencies must make various cautious decisions regarding future strong winds and heavy precipitation, e.g., reservoir discharges. This study developed a system that can forecast future rainfall time patterns and used them to enact timely typhoon-prevention measures
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