Study on Diurnal Variation of Rainfall Observed by X-band Polarimetric Radar in Peatlands Over Bengkalis Island, Eastern Sumatra, Indonesia

Understanding the precipitation systems over tropical peatlands is essential for flood and forest fire risk management. The diurnal variation of rainfall over the Indonesian maritime continent has been analyzed previously by satellite, and more recently, by analyzing data from rain gauge network across Sumatra. In the complicated topography of Bengkalis Island located between Sumatra Island and the Malay Peninsula, the ground observation network is unevenly distributed. Consequently, analyzing the regional characteristics of diurnal variations of rainfall over the region is difficult. This paper presents preliminary results from observations for five rain gauges over Bengkalis Island and high spatiotemporal resolution compact X-band polarimetric radar whose data were collected from February 2020 to June 2021. The average hourly rainfall estimates by radar was compared with rain gauge data. The average hourly rainfall mentioned above during the observation period were re-averaged for each time zone. Rainfall occurred over both sea and land areas along the coast from 20:00 to 06:00 local time (LT), and heavy rain (≥50 mm/h) occurred across Bengkalis Island from west to east after midnight from 00:00 to 03:00 LT. On the other hand, rainfall was distributed over land areas in the daytime from 10:00 to 16:00 LT. These findings showed that sea-land breeze circulation is the dominant wind system in this area.