Spatial frequency analysis of annual extreme daily precipitation across Japan

Abstract

Study region: Japan. Study focus: In this study, we analyzed the spatial frequency of annual extreme daily precipitation (AEDP) across Japan once every 100 years. A large ensemble analysis was conducted using the database for policy decision making for future climate changes (d4PDF) for precipitation data. A non-parametric method was used to calculate the AEDP amounts for each 20-km cell across Japan. New hydrological insights for the region: The results indicated that AEDP of RP100-year occurs once approximately every 1.18 years in the historical simulation across Japan. Furthermore, according to the Representative Concentration Pathway delivering 8.5 W/m2 globally (RCP 8.5), the frequency of AEDP of RP100-year increases once every 1.00 years in the +4-K future simulation. The mean of AEDP of RP100-year occurrence area with a return period of 100 years is ~10.38 cells (~4150 km2), with a median of six cells (~2400 km2). With future changes in the mean area of AEDP occurrence with a return period of 100 years predicted in RCP 8.5, there could be a massive increase in the area over which AEDP occurs (by ~2.1 times when mean values are used and with a median predicted increase of ~5.0 times the area). Additionally, we examined extreme precipitation values for various return periods using d4PDF data to consider the relationship between the scale of extreme precipitation and its probability.

Keywords

• D4PDF
• Return period
• Return area
• Median
• Global warming