ANALYZING THE UNCERTAINTY IN THE PMP ESTIMATION METHOD UNDER FUTURE CLIMATIC CONDITIONS

Abstract

 This study aims to evaluate the reasonability of future probable maximum precipitation (PMP) values estimated by the moisture-maximization method. This study utilized the d4PDF database, which is a large ensemble climate simulation output, to evaluate the estimated PMPs with sufficient extreme precipitation cases. Using the d4PDF, PMPs were estimated under historical and future climatic conditions in four target areas of Japan. The estimated PMPs in each climate condition were evaluated for their reliability with reference precipitation estimated from the annual maximum daily rainfall of d4PDF. The rate of change of PMPs between the two climate conditions was lower than that of precipitation in all areas. Compared to the reference values, historical PMPs were reasonably estimated while the future PMPs were underestimated. The future moisturemaximizing ratio (MMR) was estimated to be lower than the historical MMR as the event precipitable water (PW) had a higher change rate than the maximum PW in future climatic conditions. The lower future MMR led to a low change rate and underestimation of PMP in future climatic conditions compared to the historical ones. Consequently, the moisture-maximization method may have an uncertainty in underestimating the PMP under future climatic conditions. Therefore, it may be necessary to modify the moisture-maximization method for suitable PMP estimation under future climate conditions.