Projection of Future PMPs in Korea Using a Copula-Based Moisture Maximization Ratio

Abstract

Despite the rapid intensification of extreme rainfall due to recent climate change, the Probable Maximum Precipitations (PMPs), key design standards for hydraulic structures in Korea, have not been updated for a long period. This lack of updates raises concerns that the current standards fail to reflect actual climate risks. To address this, this study proposes a future PMPs estimation procedure tailored to Korean conditions based on the WMO (2009) hydro-meteorological method. The procedure was applied to the SSP2-4.5 and SSP5-8.5 scenarios of the EC-Earth3-Veg and HadGEM3-RA models to project future ensemble-based PMPs. In particular, conventional methods calculate the moisture maximization ratio by fixing the representative precipitable water to historical observed values. This approach tends to over-reflect the increase in future maximum precipitable water, leading to an overestimation of PMPs. To overcome this limitation, this study estimated future annual representative precipitable water based on a Copula model. By applying this to the moisture maximization ratio calculation, the issue of PMPs overestimation was effectively mitigated. However, since this study relies on the results of two climate models, inherent uncertainties exist. Therefore, future research needs to project future PMPs using a multi-model ensemble with a broader range of models to enhance reliability.

Acknowledgment

This work was supported by Korea Environment Industry & Technology Institute(KEITI) through Research and Development on the Technology for Securing the Water Resources Stability in Response to Future Change Project, funded by Korea Ministry of Climate, Energy, Environment(MCEE)(RS-2024-00332300) and by the National Research Foundation of Korea(NRF) grant funded by the Korea government(MSIT)(RS-2025-00563294).