ANALYSIS CHARACTERISTICS OF SUB-DAILY EXTREME PRECIPITATION ALONG THE UPPER CITARUM RIVER BASIN Iyya Juwita Pangesti (a), Edi Riawan(b)(c), Yogi Sahat Maruli Simanjuntak(d)
a.Department of Meteorology, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Indonesia
b.Atmospheric Science Research Group, Faculty of Earth Sciences and Technology, Bandung Institute of Technology, Indonesia
c.Center for Water Resource Development, Bandung Institute of Technology, Indonesia
d.Department of Civil Engineering (Hidraulic Laboratory), Hiroshima University, Japan
Abstract
The Upper Citarum River Basin area always experiences flooding every year, the majority of which are triggered by extreme precipitation. On the other hand, extreme precipitation characteristics with daily scale data cannot reflect the more detailed intensity and frequency of precipitation. BBWS Citarum has installed Automatic Weather Station (AWS) since 2017 with 1 hour temporal resolution. Based on the following considerations, it is necessary to analyze the sub-daily extreme precipitation characteristics in the Upper Citarum River Basin to increase flood preparedness.
This study uses the threshold of extreme rainfall by choosing the 95th percentile of all historical hourly precipitation. Then We adopted the diurnal percentage (DP) and variation of EPA/EPF/EPI. In addition, the Quality Control (QC) method is used in order to check the validity of the data.
Based on the hourly observation precipitation in 7 stations during 2017-2021, the characteristics of extreme precipitation (EP) diurnal cycle along the Upper Citarum River Basin (UCRB) and their regional and monthly differences during all season have been indicated and revealed in this study. Results show that the EP amount (EPA) over most of UCRB exhibits one diurnal peak in late afternoon. The late afternoon EPA diurnal peaks mainly resulted from the short duration EP events. However, both the short and long duration EP events lead to the nocturnal diurnal peaks. The EP events with short duration over UCRB frequently start, peak and end in late afternoon (15:00) Jakarta Time, and EP events with long duration over south of UCRB (Kertasari) frequently start in the afternoon and typically end at around 14:00 and 18:00-19:00 Jakarta time. Meanwhile, the EP frequency (EPF) diurnal cycles over most of UCRB exhibit obvious monthly differences in all season, which show a dominant peak in February. These results are very important to improve the accuracy of flood modeling and flood prediction.
Keywords: Sub-daily- Extreme rainfall- Upper Citarum River Basin (UCRB)
