Addressing Climate Internal Variability on Future Intensity-Duration-Frequency Curves at Fine Scales across South Korea

Manh Van Doi,Jongho Kim

doi:10.3390/w13202828

Abstract

Designing water infrastructure requires information about the magnitude and frequency of upcoming rainfall. A limited range of data offers just one of many realizations that occurred in the past or will occur in the future; thus, it cannot sufficiently explain climate internal variability (CIV). In this study, future relationships among rainfall intensity (RI), duration, and frequency (called the IDF curve) are established by addressing the CIV and tail characteristics with respect to frequency. Specifically, 100 ensembles of 30-year time series data were created to quantify that uncertainty. Then, the tail characteristics of future extreme rainfall events were investigated to determine whether they will remain similar to those in the present. From the RIs computed for control and future periods under two emission scenarios, following are the key results. Firstly, future RI will increase significantly for most locations, especially near the end of this century. Secondly, the spatial distributions and patterns indicate higher RI in coastal areas and lower RI for the central inland areas of South Korea, and those distributions are similar to those of the climatological mean (CM) and CIV. Thirdly, a straightforward way to reveal whether the tail characteristics of future extreme rainfall events are the same as those in the present is to inspect the slope value for the factor of change (FOC), mFOC. Fourthly, regionalizing with nearby values is very risky when investigating future changes in precipitation frequency estimates. Fifthly, the magnitude of uncertainty is large when the data length is short and gradually decreases as the data length increases for all return periods, but the uncertainty range becomes much greater as the return period becomes large. Lastly, inferring future changes in RI from the CM is feasible only for small return periods and at locations where mFOC is close to zero.

Highlights

Designing water infrastructure to ensure its safety and longevity while attaining its intended purpose requires information about the magnitude and frequency of upcoming rainfall and floods
We focus on: (1) estimating future changes in precipitation frequency estimates for each location; (2) comparing the tail characteristics of precipitation extremes in future periods with those in the control period in terms of the return period; (3) investigating how climate internal variability (CIV)
The generalized extreme value (GEV) and Gumbel distributions were selected because they had been suggested by previous studies in South Korea [7,51]

Summary

Introduction

Designing water infrastructure to ensure its safety and longevity while attaining its intended purpose requires information about the magnitude and frequency of upcoming rainfall and floods. IDF curves at smaller scales are derived indirectly by searching for scaling factors in the relationships of IDF curves at larger and smaller scales and assuming that they will not change in the future [7,8,9]. Another option is to calculate the IDF curve directly after creating a small-scale time series using methods, such as random multiplication cascades [10], the fragment method [11,12], and

Results

Discussion

Conclusion