• Journal of Korea Water Resources Association
• /
• v.48 no.6
• /
• pp.451-461
• /
• 2015

This study aimed to estimate the future design rainfall through a non-stationary frequency analysis using the rainfall separation technique. First, we classified rainfall in the Korean Peninsula into local downpour and TC-induced rainfall through rainfall separation technique based on the path and size of a typhoon. Furthermore, we performed the analysis of regional rainfall characteristics and trends. In addition, we estimated the future design rainfall through a non-stationary frequency analysis using Gumbel distribution and carried out its quantitative comparison and evaluation. The results of the analysis suggest that the increase and decrease rate of rainfall in the Korean Peninsula were different and the increasing and decreasing tendencies were mutually contradictory at some points. In addition, a non-stationary frequency analysis was carried out by using the rainfall separation technique. The outcome of this analysis suggests that a relatively reasonable future design rainfall can be estimated. Comparing total rainfall with the future design rainfall, differences were found in the southern and eastern regions of the Korean peninsula. This means that climate change may have a different effect on the typhoon and local downpour. Thus, in the future, individual assessment of climate change impacts needs to be done through moisture separation. The results presented here are applicable in future hydraulic structures design, flood control measures related to climate change, and policy establishment.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2005.05b
• /
• pp.593-598
• /
• 2005

At-site analysis is not appropriate if the record length is shorter than target return period T. If the record length is longer than 27 years, then at-site analysis may be sufficient(Institute of Hydrology, 1999). However, in such a case, regional frequency analysis is recommended for purpose of comparison. Record lengths of annual maximum rainfall data in Korea are usually shorter than 50 years. It is therefore essential to apply regional frequency analysis for estimating rainfall quantiles of more than 100 years return period. In this research, regional rainfall frequency analysis is performed for hourly rainfall data of South Korea. Homogeneous regions are idntified by clusgter analysis which is a standard method of statistical multivariate analysis for dividing a data set into groups. An appropriate distribution is chosen by goodness-of-fit test. GLO is found to be an appropriate distribution as a result of goodness-of-fit measure (Hosking & Wallis, 1997). Simulation experiments are performed to check the performance of frequency analysis techniques. The effects of discordant sites on quantiles are considered.

• Journal of Korea Water Resources Association
• /
• v.43 no.2
• /
• pp.187-199
• /
• 2010

This study evaluated applicability and confidence of probability rainfalls estimated by the non-stationary rainfall frequency analysis which was recently developed. Using rainfall data at 4 sites which have an obvious increasing trend in observations, we estimated 3 type probability rainfalls; probability rainfalls from stationary rainfall frequency analysis using data from 1973-1997, probability rainfalls from stationary rainfall frequency analysis using data from 1973-2006, probability rainfalls from non-stationary rainfall frequency analysis assuming that the current year is 1997 and the target year is 2006. Based on the comparison of residuals from 3 probability rainfalls, the non-stationary rainfall frequency analysis provided more effective and well-directed estimates of probability rainfalls in the target year. Using Bootstrap resampling, this study also evaluated the parameter estimation methods for the non-stationary rainfall frequency analysis based on confidence intervals. The confidence interval length estimated by the maximum likelihood estimation (MLE) is narrower than the probability weighted moments (PWM). The results indicated that MLE provides more proper confidence than PWM for non-stationary probability rainfalls.

• Proceedings of the Korea Water Resources Association Conference
• /
• 2007.05a
• /
• pp.1619-1624
• /
• 2007

The rainfall frequency estimations are critical in the design of hydraulic structures (such as bridges and culverts) to ensure that they are built economically and safely. In other words, they are not over designed or under designed. However one of the main assumptions in the creation of these analysis is that the rainfall data for a site is stationary. That is, climatic trends and variability in a region have negligible effects on the curves. But as has been proved in recent history, climatic variability and trends do exist and their effects on precipitation have not been negligible. Increasing occurrences of the El Nino phenomenon have lead to droughts and floods around the world, and long term trends in rainfall, both increases and decreases, have been seen in all regions across Korea. The purpose of this paper is to investigate and evaluate impacts of ENSO on rainfall characteries and rainfall frequency estimations in Korea. In this paper, The available rainfall data were categorized into Warm(EL Nino), Cold(La Nina), Normal episodes based on the Cold & Warm Episodes by Season then 50 years of daily rainfall data were generated for each episodic events(EL Nino, La Nina)

• Magazine of the Korean Society of Agricultural Engineers
• /
• v.45 no.5
• /
• pp.97-109
• /
• 2003

This study is mainly conducted to derive the design drought rainfall by the consecutive duration using probability weighted moments with rainfall in the regional drought frequency analysis. It is anticipated to suggest optimal design drought rainfall of hydraulic structures for the water requirement and drought frequency of occurrence for the safety of water utilization through this study. Preferentially, this study was conducted to derive the optimal regionalization of the precipitation data that can be classified by the climatologically and geographically homogeneous regions all over the regions except Cheju and Ulreung islands in Korea. Five homogeneous regions in view of topographical and climatological aspects were accomplished by K-means clustering method. Using the L-moment ratio diagram and Kolmogorov-Smirnov test, generalized extreme value distribution was confirmed as the best fitting one among applied distributions. At-site and regional parameters of the generalized extreme value distribution were estimated by the method of L-moments. Design drought rainfalls using L-moments following the consecutive duration were derived by the at-site and regional analysis using the observed and simulated data resulted from Monte Carlo techniques. Relative root-mean-square error (RRMSE), relative bias (RBIAS) and relative reduction (RR) in RRMSE for the design drought rainfall derived by at-site and regional analysis in the observed an simulated data were computed and compared. In has shown that the regional frequency analysis procedure can substantially more reduce the RRMSE. RBIAS and RR in RRMSE than those of at-site analysis in the prediction of design drought rainfall. Consequently, optimal design drought rainfalls following the regions and consecutive durations were derived by the regional frequency analysis.

• 한국방재학회:학술대회논문집
• /
• 2007.02a
• /
• pp.575-578
• /
• 2007

The objective of this study is to analyze the regionalization of point rainfall by statistical methods for regional frequency analysis of the rainfall. The rainfall data used in this study are annual maximum rainfall at 57 stations during the period of more than 30 years for 12 durations(10min, 1, 2, 3, 4, 5, 6, 8, 10, 12, 18, 24hr) in Korea. The Mann-Whitney U test, Kruskal-Wallis one-way analysis of variance of nonparametric test the principal component and the cluster analysis have been performed to analyze the regionalization of rainfall. The results of this study are as follows; (1) The region which hydrological homogeneous is accepted does not exist for whole duration in Korea. (2) The result of nonpametric test shows that hydrological homogeneous regions of point rainfall are divided by 5 regions. (3) In case of cluster analysis hydrological homogeneous regions of point rainfall are divided by 6 regions and 4 other areas.

• Journal of Wetlands Research
• /
• v.2 no.1
• /
• pp.49-58
• /
• 2000

The frequency analysis of annual maximum rainfall data and the derivation of probable rainfall intensity formula at Masan station are performed in this study. Based on the eight different rainfall duration data from 10 minutes to 24 hours, eight types of probability distribution (Gamma, Lognormal, Log-Pearson type III, GEV, Gumbel, Log-Gumbel, Weibull, and Wakeby distributions), three types of parameter estimation scheme (moment, maximum likelihood and probability weighted methods) and three types of goodness-of-fit test (${\chi}^2$, Kolmogorov-Smirnov and Cramer von Mises tests) were considered to find an appropriate probability distribution at Masan station. The Lognormal-2 distribution was selected and the probable rainfall intensity formula was derived by regression analysis. The derived formula can be used for estimating rainfall quantiles of the Masan vicinity areas with convenience and reliability in practice.

• Journal of the Korea Institute of Military Science and Technology
• /
• v.13 no.2
• /
• pp.227-234
• /
• 2010

When a weapon system is developed, climate elements such as temperature, rainfall, and so on have an effect on development costs and a developing period. Therefore, effects of environment and climate must be examined throughly before the design of weapon systems and be applied to their developments. And so, operational and storage requirements for weapon systems are determined and are applied to related tests through analyzing not only environmental factors such as vibration, shock, and so on, but also climate factors. In this paper, the distribution and the frequency of occurrence of rainfall were analyzed and were suggested as a good guide to determine standards of tests for weapon systems when it's raining.

• Journal of Korea Water Resources Association
• /
• v.37 no.5
• /
• pp.425-435
• /
• 2004

Mainly, observed maximum rainfall has been evaluated by point rainfall, but actually it should be considered by means of average areal rainfall. Average areal rainfall is an estimated value computed through DAD(rainfall Depth-Area-Duration) analysis. By using this value, an average and maximum areal rainfall according to area-duration relationship could be computed. In this study, we assume that the whole Korea region is hydrologically homogeneous, and then analyze using the storm-centered DAD(moving-area DAD) method for the past century data. From this analysis, we evaluate the yearly variation of observed maximum areal rainfall through area-duration relationship. And we also construct an IDF(rainfall Intensity-Duration-Frequency) curve by using the annual time series data which is composed of maximum areal rainfall. The characteristics of IDF and observed maximum areal rainfall is also evaluated.

• Proceedings of the Korean Society of Agricultural Engineers Conference
• /
• 2002.10a
• /
• pp.237-240
• /
• 2002

Design rainfall using LH-moments following the consecutive duration were derived by the regional and at-site analysis using the observed and simulated data resulted from Monte Carlo techniques. RRMSE, RBIAS and RR in RRMSE for the design rainfall were computed and compared in the regional and at-site frequency analysis. Consequently, it was shown that the regional analysis can substantially more reduce the RRMSE, RBIAS and RR in RRMSE than at-site analysis in the prediction of design rainfall. RE for an optimal order of L-moments was also computed by the methods of L, L1, L2, L3 and L4-moments for GEV distribution. It was found that the method of L-moments is more effective than the others for getting optimal design rainfall according to the regions and consecutive durations in the regional frequency analysis. Diagrams for the design rainfall derived by the regional frequency analysis using L-moments were drawn according to the regions and consecutive durations by GIS techniques.