QUANTIFICATION AND PROJECTION OF SHORT-TERM RAINFALL CHARACTERISTICS IN PHNOM PENH CITY

Abstract

 Frequent flooding has been occurring in the central Phnom Penh City area, chronically affecting daily life, health and various socio-economical activities. Among them, the characteristics of the rainfall, especially for the shorter time scale ranging from hourly to daily, are poorly understood because of the limited measurement data of rainfall, thus it is still challenging to find a comprehensive and quantitative view of current and future rainfall characteristics in this region. The analysis indicated that the heavy rainfalls are frequent in recent years and they have more acute temporal variations than ever recognized by the intensity-duration curves. With the statistical bias correction and downscaling of GCM outputs, hourly rainfall intensity is projected to increase by 20 % to 80 % than current design rainfall, depending on GCM used for the analysis. The spatial variations are found to be very large, but no significant difference was found for the monthly totals. Because of the lack of reliable long-term hourly or sub-daily rainfall records, we evaluated the 3-hourly rainfall extremes from the MSWEP, and it was concluded it was difficult to use it for quantification of the rainfall for a short time.