Spatiotemporal characteristics and hydrological implications of downscaled hourly precipitation climate scenarios for South Korea

Abstract

The assessment of hydrometeorological variables using climate scenario data derived from global climate models (GCMs) is essential for adapting and mitigating climate-induced changes. However, GCM outputs are too coarse to apply at the basin scale. Therefore, spatial downscaling of GCM outputs has been widely used to assess hydrological changes on the basin scale. Temporal downscaling is also required to obtain hourly precipitation data for small or medium basin analysis because only several hours of data are required to determine peak flows after rainfall. This study presents the spatiotemporal distribution of downscaled hourly precipitation over South Korea for two representative concentration pathway scenarios (RCP4.5 and RCP8.5), as well as its implications over hydrological responses. Under the RCP8.5 scenario, the mean hourly precipitation significantly increases over the southern part of South Korea, especially during the morning, with a smaller increase at later times of the day. However, this increase is not propagated to the mainland because of mountainous areas in the southern part of the country. Furthermore, the hydrological responses determined by a distributed rainfall-runoff model reveal a significant increase in the peak flow under the RCP8.5 scenario but a slight decrease under the RCP4.5 scenario. In addition, the observed relation between extreme precipitation and temperature is compared with that under RCP8.5. The results indicate that the downscaled hourly precipitation data adequately reproduce the observed relationship. We conclude that the temporal downscaling method used in this study is suitable for obtaining hourly precipitation data from daily GCM scenarios. In addition, rainfall-runoff simulations using downscaled hourly precipitation data are useful for investigating hydrological response variability related to future climate scenarios.