The Experts below are selected from a list of 475107 Experts worldwide ranked by ideXlab platform
Minha Choi - One of the best experts on this subject based on the ideXlab platform.
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constructing Rainfall depth frequency curves considering a linear trend in Rainfall observations
Stochastic Environmental Research and Risk Assessment, 2012Co-Authors: Minha Choi, Hyunhan KwonAbstract:Comprehensive flood prevention plans are established in large basins to cope with recent abnormal floods in South Korea. In order to make economically effective plans, appropriate design Rainfalls are critically determined from the Rainfall depth-frequency curves which take the occurrence of abnormal floods into consideration. Conventional approaches to construct the Rainfall depth-frequency curves are based on the stationarity assumption. However, this assumption has a critical weak aspect in that it cannot reflect non-stationarities in Rainfall observations. As an alternative, this study suggests the non-stationary Gumbel model (NSGM) which incorporates a linear trend of Rainfall observations into Rainfall frequency analysis to construct the Rainfall depth-frequency curves. A comparison of various schemes employed in the model found that the proposed NSGM permits the estimation of the distribution parameters even when shifted in the future by using linear relationships between Rainfall statistics and distribution parameters, and produces more acceptable estimates of design Rainfalls in the future than the conventional model. The NSGM was applied at several stations in South Korea and then expected the design Rainfalls to increase by up to 15–30% in 2050.
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application of bivariate frequency analysis to the derivation of Rainfall frequency curves
Stochastic Environmental Research and Risk Assessment, 2010Co-Authors: Gunhui Chung, Minha ChoiAbstract:Bivariate distributions have been recently employed in hydrologic frequency analysis to analyze the joint probabilistic characteristics of multivariate storm events. This study aims to derive practical solutions of application for the bivariate distribution to estimate design Rainfalls corresponding to the desired return periods. Using the Gumbel mixed model, this study constructed Rainfall–frequency curves at sample stations in Korea which provide joint relationships between amount, duration, and frequency of storm events. Based on comparisons and analyses of the Rainfall–frequency curves derived from univariate and bivariate storm frequency analyses, this study found that conditional frequency analysis provides more appropriate estimates of design Rainfalls as it more accurately represents the natural relationship between storm properties than the conventional univariate storm frequency analysis.
Hyunhan Kwon - One of the best experts on this subject based on the ideXlab platform.
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stochastic extreme downscaling model for an assessment of changes in Rainfall intensity duration frequency curves over south korea using multiple regional climate models
Journal of Hydrology, 2017Co-Authors: Jinyoung Kim, Hyunhan Kwon, Carlos H R LimaAbstract:Abstract A conditional copula function based downscaling model in a fully Bayesian framework is developed in this study to evaluate future changes in intensity–duration frequency (IDF) curves in South Korea. The model incorporates a quantile mapping approach for bias correction while integrated Bayesian inference allows accounting for parameter uncertainties. The proposed approach is used to temporally downscale expected changes in daily Rainfall, inferred from multiple CORDEX-RCMs based on Representative Concentration Pathways (RCPs) 4.5 and 8.5 scenarios, into sub-daily temporal scales. Among the CORDEX-RCMs, a noticeable increase in Rainfall intensity is observed in the HadGem3-RA (9%), RegCM (28%), and SNU_WRF (13%) on average, whereas no noticeable changes are observed in the GRIMs (−2%) for the period 2020–2050. More specifically, a 5–30% increase in Rainfall intensity is expected in all of the CORDEX-RCMs for 50-year return values under the RCP 8.5 scenario. Uncertainty in simulated Rainfall intensity gradually decreases toward the longer durations, which is largely associated with the enhanced strength of the relationship with the 24-h annual maximum Rainfalls (AMRs). A primary advantage of the proposed model is that projected changes in future Rainfall intensities are well preserved.
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constructing Rainfall depth frequency curves considering a linear trend in Rainfall observations
Stochastic Environmental Research and Risk Assessment, 2012Co-Authors: Minha Choi, Hyunhan KwonAbstract:Comprehensive flood prevention plans are established in large basins to cope with recent abnormal floods in South Korea. In order to make economically effective plans, appropriate design Rainfalls are critically determined from the Rainfall depth-frequency curves which take the occurrence of abnormal floods into consideration. Conventional approaches to construct the Rainfall depth-frequency curves are based on the stationarity assumption. However, this assumption has a critical weak aspect in that it cannot reflect non-stationarities in Rainfall observations. As an alternative, this study suggests the non-stationary Gumbel model (NSGM) which incorporates a linear trend of Rainfall observations into Rainfall frequency analysis to construct the Rainfall depth-frequency curves. A comparison of various schemes employed in the model found that the proposed NSGM permits the estimation of the distribution parameters even when shifted in the future by using linear relationships between Rainfall statistics and distribution parameters, and produces more acceptable estimates of design Rainfalls in the future than the conventional model. The NSGM was applied at several stations in South Korea and then expected the design Rainfalls to increase by up to 15–30% in 2050.
Yeoukoung Tung - One of the best experts on this subject based on the ideXlab platform.
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bivariate frequency analysis of Rainfall intensity and duration for urban stormwater infrastructure design
Journal of Hydrology, 2017Co-Authors: Changhyun Jun, Yeoukoung Tung, Xiaosheng Qin, Thian Yew Gan, Carlo De MicheleAbstract:Abstract This study presents a storm-event based bivariate frequency analysis approach to determine design Rainfalls in which, the number, intensity and duration of actual rainstorm events were considered. To derive more realistic design storms, the occurrence probability of an individual rainstorm event was determined from the joint distribution of storm intensity and duration through a copula model. Hourly Rainfall data were used at three climate stations respectively located in Singapore, South Korea and Canada. It was found that the proposed approach could give a more realistic description of Rainfall characteristics of rainstorm events and design Rainfalls. As results, the design Rainfall quantities from actual rainstorm events at the three studied sites are consistently lower than those obtained from the conventional Rainfall depth-duration-frequency (DDF) method, especially for short-duration storms (such as 1-h). It results from occurrence probabilities of each rainstorm event and a different angle for Rainfall frequency analysis, and could offer an alternative way of describing extreme Rainfall properties and potentially help improve the hydrologic design of stormwater management facilities in urban areas.
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establishing Rainfall depth duration frequency relationships at daily raingauge stations in hong kong
Journal of Hydrology, 2013Co-Authors: Peishi Jiang, Yeoukoung TungAbstract:Summary Rainfall intensity (depth)–duration–frequency (IDF/DDF) relationships provide information essential for urban stormwater drainage system design and other hydrosystem infrastructures. For catchments where drainage areas are small, Rainfall DDF relationships with short duration can be established based on Rainfall records from automatic raingauges. Due to the progression of technology development, wide spread installation of automatic raingauges does not happen until 2–3 decades ago. Therefore, record lengths at majority of automatic raingauges are relatively short and the derived Rainfall DDF relationships on the basis of at-site frequency analysis are potentially subject to significant sampling error. On the other hand, many conventional raingauges exist long before automatic raingauges were deployed. However, daily Rainfall data with long records at conventional raingauges are of limited use to establish Rainfall DDF relationships in areas with small catchment size like Hong Kong where design storm duration significantly shorter than 24-h are needed. This study presents a practical methodological framework to derive Rainfall DDF relationships with short duration at conventional raingauge locations. The core components of the framework include the scaling model of Rainfalls of different durations, the establishment of relationship between annual maximum daily Rainfall and rolling-time 1440 min Rainfall, the quantification of statistical features of estimated annual maximum 1440 min Rainfalls, and the assessment of uncertainty of derived Rainfall DDF relationships at conventional raingauges.
Carlo De Michele - One of the best experts on this subject based on the ideXlab platform.
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bivariate frequency analysis of Rainfall intensity and duration for urban stormwater infrastructure design
Journal of Hydrology, 2017Co-Authors: Changhyun Jun, Yeoukoung Tung, Xiaosheng Qin, Thian Yew Gan, Carlo De MicheleAbstract:Abstract This study presents a storm-event based bivariate frequency analysis approach to determine design Rainfalls in which, the number, intensity and duration of actual rainstorm events were considered. To derive more realistic design storms, the occurrence probability of an individual rainstorm event was determined from the joint distribution of storm intensity and duration through a copula model. Hourly Rainfall data were used at three climate stations respectively located in Singapore, South Korea and Canada. It was found that the proposed approach could give a more realistic description of Rainfall characteristics of rainstorm events and design Rainfalls. As results, the design Rainfall quantities from actual rainstorm events at the three studied sites are consistently lower than those obtained from the conventional Rainfall depth-duration-frequency (DDF) method, especially for short-duration storms (such as 1-h). It results from occurrence probabilities of each rainstorm event and a different angle for Rainfall frequency analysis, and could offer an alternative way of describing extreme Rainfall properties and potentially help improve the hydrologic design of stormwater management facilities in urban areas.
Carlos H R Lima - One of the best experts on this subject based on the ideXlab platform.
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stochastic extreme downscaling model for an assessment of changes in Rainfall intensity duration frequency curves over south korea using multiple regional climate models
Journal of Hydrology, 2017Co-Authors: Jinyoung Kim, Hyunhan Kwon, Carlos H R LimaAbstract:Abstract A conditional copula function based downscaling model in a fully Bayesian framework is developed in this study to evaluate future changes in intensity–duration frequency (IDF) curves in South Korea. The model incorporates a quantile mapping approach for bias correction while integrated Bayesian inference allows accounting for parameter uncertainties. The proposed approach is used to temporally downscale expected changes in daily Rainfall, inferred from multiple CORDEX-RCMs based on Representative Concentration Pathways (RCPs) 4.5 and 8.5 scenarios, into sub-daily temporal scales. Among the CORDEX-RCMs, a noticeable increase in Rainfall intensity is observed in the HadGem3-RA (9%), RegCM (28%), and SNU_WRF (13%) on average, whereas no noticeable changes are observed in the GRIMs (−2%) for the period 2020–2050. More specifically, a 5–30% increase in Rainfall intensity is expected in all of the CORDEX-RCMs for 50-year return values under the RCP 8.5 scenario. Uncertainty in simulated Rainfall intensity gradually decreases toward the longer durations, which is largely associated with the enhanced strength of the relationship with the 24-h annual maximum Rainfalls (AMRs). A primary advantage of the proposed model is that projected changes in future Rainfall intensities are well preserved.
