Assessment of the ENSO Impact on Rainfall Characteristics and Frequency Analysis in South Korea

摘要

Intensity-Duration-Frequency (IDF) curves are a form of frequency analysis usedby engineers and scientists to create flood frequency estimations (Pilgrim, 2001).These frequency analyses are very important in the design of hydraulic structures toensure that they are built economically and safely, that is, they are not over-designedor under-designed. IDF curves have traditionally been created by using historicaldata collected at a site and by assuming that this rainfall series is stationary andrepresentative of the future. But as it has been proved in recent observations, climaticvariability and trends do exist and their effects on rainfall have not been negligible.Increasing occurrences of the El Nino and La Nina phenomenon have lead todroughts and floods around the world, and long-term trends in rainfall have beenseen in all regions across Korea.The purpose of this paper is to evaluate impacts of ENSO on rainfall characteristicsand IDF curves in South Korea. In this paper, first, rainfall data in 60 climate stationswere categorized into Warm (EL Nino), Cold (La Nina), Normal episodes based onthe Cold & Warm Episodes by Season, then 100 years of daily rainfall data weregenerated for each episodic event(EL Nino, La Nina) using Markov chain MonteCarlo(MCMC) model. Finally, IDF curve analysis and comparison for each episodewere conducted. From the results, it shows that there are significant changes in therainfall characteristics and IDF curves among Warm (EL Nino), Cold (La Nina) andNormal episodes.