Abstract:

[Objective] Variations in precipitation are important references for reservoir storage and scheduling. This study aims to reveal the precipitation patterns in the catchment area of the Hedi Reservoir under typhoons with different track types (west-track, middle-track, east-track), establish related forecasting experience, and improve typhoon precipitation forecast services. [Methods] Using typhoon track data, daily precipitation observations from monitoring stations in the catchment area, and MICAPS data, statistical methods including linear trend analysis and Morlet wavelet analysis were used to investigate the variation characteristics of typhoon precipitation and the circulation pattern configurations of typhoon-induced rainstorms affecting the catchment area of Hedi Reservoir. [Results] The results showed that: (1) over the past 32 years, the number of typhoons affecting the catchment area showed an increasing trend of 0.33 events per decade, with a 7-year periodic oscillation. The peak typhoon season occurred from July to September, accounting for 77.2% of annual typhoon impact.(2) Typhoon tracks affecting the catchment area were classified into three types: west-track, middle-track, and east-track. Middle-track type was the most frequent, accounting for 46.8% of the total, followed by west-track type at 44.3%, while east-track type was the least frequent, accounting for 8.9%.(3) There were significant differences in precipitation characteristics among typhoons with different track types. West-track typhoons showed large variations in precipitation amount and intensity, with stronger precipitation in the southern catchment area and frequent localized rainstorms. Middle-track typhoons were characterized by large rainfall amounts, extensive areas of intense precipitation, and relatively prolonged duration, with rainstorms to heavy rainstorms dominating the entire catchment area. For east-track typhoons, rainfall amounts varied greatly across stations, and there was currently no reliable forecasting experience.(4) The typhoon-induced rainstorms in the upstream catchment area of Hedi Reservoir were mainly caused by the combined influence of the western Pacific subtropical high, the southwest monsoon, and cold air. Based on an analysis of historical typhoon circulation patterns, an empirical forecasting method for the circulation patterns of west-track and middle-track typhoon-induced rainstorms was preliminarily developed. [Conclusion] The results of this study indicate that the precipitation in the catchment area of the Hedi Reservoir is closely related to typhoon tracks. Forecasting of typhoon tracks and empirical prediction of their circulation patterns can serve as a reference for accurately forecasting reservoir precipitation. These findings provide important guidance for the rational operation of the Hedi Reservoir, coordinated water storage scheduling, meteorological disaster prevention and mitigation, and the full realization of maximum comprehensive benefits.

Key words: catchment area, precipitation change characteristics, circulation flow pattern, typhoon, precipitation observation data, Micaps data, Hedi Reservoir, reservoir storage and forecast