• Proceedings of the Korean Society of Crop Science Conference
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• 2000.11a
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• pp.3-11
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• 2000

The Asian summer monsoon has a profound social and economic impact in East Asia and its surrounding countries. The monsoon is basically a response of the atmosphere to the differential heating between the land mass of the Asian continent and the adjacent oceans. The atmospheric response, however, is quite complicated due to the interactions between the atmospheric heat sources, land-sea contrast, and topography, The occurrence of extreme summertime floods in Korea, Japan, and China in 1998 and 1999 has highlighted the range of variability of the East Asian summertime monsoon circulation and spurred interest in investigating the cause of such extreme variability. While ENSO is often considered a prime mechanism responsible for the unusual hydrological disasters in East Asia, understanding of the connection between ENSO and the East Asian monsoon is hampered by their dynamic complexities. Along with a recent phenomenon of weather abnormalities observed in many parts of the globe, Korea has seen its share of increased weather abnormalities such as the record-breaking heavy rainfalls due to a series of flash floods in the summers of 1998 and 1999, following devastating Yangtze river floods in China. A clear regime shift is found in the tropospheric mean temperature in the northern hemisphere middle latitudes and the surface temperature over the Asian continent during the summer with a sudden warming since 1977. Either decadal climate variation or climate regime shift in the Asian continent is evident and may have altered the characteristics of the East Asian summer monsoon. Considering the summertime rainfall amount in Korea is overall increased lately, the 1998/99 heavy rainfalls may not be isolated episodes related only to ENSO, but could be a part of long-term climate variation. The record-breaking heavy summer rainfalls in Korea may not be direct impact of ENSO. Instead, the effects of decadal climate variation and ENSO may be coupled to each other and also to the East Asian summer monsoon system, while their individual impacts are difficult to separate.

• Journal of Environmental Health Sciences
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• v.24 no.1
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• pp.62-69
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• 1998

It has been studied that the measurement of odor component emission at confectionery manufacture. The objects of this study were to investigate reduction of offensive odor. The survey effects of odorous materials are presented as follows. The countermeasure of operating process is to minimize sludge sediment in each unit facility. Especially, in summer, we have to clean the sludge frequently, because anaerobic decomposing is likely to occur easily. The sludge or scum from sedimentation tank pond, and floating tank should be treated quickly. We should avoid overloading operation. In the case of overloading, dissolved oxygen should be increased, the quality of wastewater input should be decreased. When dried cakes from condense tank or floating tank are left in treatment plant, we should cover, to prevent diffusion of smell with masking materials. The seasonal condition of operating should be fixed and the kind of coagulants should be changed because the wastewater in each season have different loading rates and organic materials. Odorous materials are very sensitive to the seasonal temperature variation. Especially, when the amount of rainfall is small and the high temperature of maintenance in long periods, air diffusion rate is large, so odorous materials can make great effect on surroundings comparision with other periods. To reduce odorous gas, as short term method, we had better take ceramic addition method. Especially, in summer we should take ceramic addition method. Also, as long term method, the size of wastewater treatment facility is the most important in the normal operating of wastewater treatment facility. But wastewater treatment facilities in this factory are too old, treatment process is old fashion, and the size is too small. So, large wastewater quantity to treat in summer. As results, the expansion of wastewater treatment facility and the process of improvement are required. Restriction level of odor was exceed. As it is overloaded in summer, the basis cause of odor is that the size of wastewater treatment facility is small. The prediction of air quality equilibrium density variation show that the odorous materials from working place are Amine materials whose smell strength is about 2.5(a little strong degree). We can suppose that in summer is sensitive to temperature variation, smell strength is larger as to reduce the origin of odor. We must expand wastewater treatment facility and improve the process A.S.A.P.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.38 no.2
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• pp.249-259
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• 2018

More than half of annual rainfall occurs in summer season in Korea due to its climate condition and geographical location. A frequency analysis is mostly adopted for designing hydraulic structure under the such concentrated rainfall condition. Among the various distributions, univariate Gumbel distribution has been routinely used for rainfall frequency analysis in Korea. However, the distributional changes in extreme rainfall have been globally observed including Korea. More specifically, the univariate Gumbel distribution based rainfall frequency analysis is often fail to describe multimodal behaviors which are mainly influenced by distinct climate conditions during the wet season. In this context, we purposed a Gumbel mixture distribution based rainfall frequency analysis with a Bayesian framework, and further the results were compared to that of the univariate. It was found that the proposed model showed better performance in describing underlying distributions, leading to the lower Bayesian information criterion (BIC) values. The mixed Gumbel distribution was more robust for describing the upper tail of the distribution which playes a crucial role in estimating more reliable estimates of design rainfall uncertainty occurred by peak of upper tail than single Gumbel distribution. Therefore, it can be concluded that the mixed Gumbel distribution is more compatible for extreme frequency analysis rainfall data with two or more peaks on its distribution.

• Korean Journal of Ecology and Environment
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• v.35 no.3 s.99
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• pp.160-171
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• 2002

The impact of summer monsoon on water quality of the lower Nakdong River was evaluated during the summer (June-August) in 1997. Several limnological variables were measured in the interval of $1{\sim}3$ day using an automatic monitoring system (Hydrolab $Recorder^{TM}$) to detect water quality changes caused by rainfall on onehour basis. During the monsoon period (from late June to mid July), 5 times of major rainfall events of >50 mm were recorded in the river basin. Dynamic changes of water quality were observed during the monsoon, and the first rainfall event (June$25{\sim}27$) had a significant influence on the water quality at the lower part of the river. All Parameters were largely changed due to the first rain event, and the changed level was maintained until the end of monsoon period. Nutrient concentrations and turbidity increased and values of the other parameters were declined as a result of water dilution. This rainfall event, Changma, is a meteorological phenomenon caused by the East-Asian monsoon climate. The magnitude and frequency of the rainfall during the early monsoon play an important role in change of water quality and ecosystem characteristics of large river systems.

• Journal of the Korean Institute of Intelligent Systems
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• v.26 no.1
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• pp.1-8
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• 2016

The Korea Meteorological Administration has operated the Automatic Weather Stations, of the average 13 km horizontal resolution, to observe rainfall. However, an additional RADAR network also has been operated in all-weather conditions, because AWS network could not observed rainfall over the sea. In general, the rain rate is obtained by estimating the relationship between the radar reflectivity (Z) and the rainfall (R). But this empirical relationship needs to be optimized on the rainfall over the Korean peninsula. This study was carried out to optimize the Z-R relationship in the summer of 2014 using a parallel Micro Genetic Algorithm. The optimized Z-R relationship, $Z=120R^{1.56}$, using a micro genetic algorithm was different from the various Z-R relationships that have been previously used. However, the landscape of the fitness function found in this study looked like a flat plateau. So there was a limit to the fine estimation including the complex development and decay processes of precipitation between the ground and an altitude of 1.5km.

• Journal of Korea Water Resources Association
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• v.30 no.2
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• pp.165-175
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• 1997

This is to study the characteristics of available water resources (AWR) of the eastern coastal area in Korea. A rating curve was suggested at Yangyang water level station of the Yangyangnamdai river. Annual mean precipitation of this area is 1365.8mm. Annual mean precipitation in central and northern area of eastern coastal area is more than that of southern area because of orographic precipitation occurred by the north-easterly air flow from the East sea. By the correlation analysis of monthly rainfall depths between rainfall gauging stations it is presented that the rainfall gauging stations located in coastal region have the regional representativity, but the rainfall gauging stations located in the westward of mountains have a strong locality. AWR of eastern coastal area by the application of runoff coefficient 0.665 is 1134.5X106m3 and 28.6 percentage for total water resources. In each watershed AWR is 193.7X106m3 in the Yangyangnamdai river, 109X106m3 in the Kangnungnamdai river, and 146.0X106m3 in the Samcheokosip river. The seasonal changes of 30/3% in summer and 19.1% in water, and those of the AWR to total water resources are 86.3% in winter, 60.1% in spring, 50.1% in autumn, and 25.7% in summer. The results of this study may be used to establish the water resources planning of eastern coastal area.

• Journal of Korea Water Resources Association
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• v.35 no.1
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• pp.25-36
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• 2002

Window Probability Matching Method(WPMM) is achieved by matching identical probability density of rain intensities and radar reflectivities taken only from small window centered about the gage. The equation of $Z_{e}-R$ relationship is obtained and compared with data between a DWSR-88C radar and high density rain gage networks within 150km from radar site in summer season, 1998. The probability density of radar effective reflectivity is distributed with high frequency near 15dBZ. The frequency distribution of rain intensities shows that rain intensity is lower than 10mm/hr in most part of radar coverage area. As the result of $Z_{e}-R$ relationship using WPMM, curved line has shown to the log scale spatially and it can be explained more flexible than any straight-line power laws at the transformation to the rainfall amount from $Z_e$ value. During 3 months, total radar cumulative rainfall amount estimated by $Z=200R^{1.6}$ and WPMM relationships are 44 and 80 percentages of total raingage amount, respectively. Therefore, $Z_{e}-R$ relationships by WPMM may be widely needed a statistical method for the computation of accumulated precipitation.

• Journal of Korean Society on Water Environment
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• v.32 no.1
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• pp.30-35
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• 2016

Urban areas generate large amounts of stormwater and non-point source (NPS) pollutants during rainfall events. These are caused by various land use runoffs, vehicular and human activities and increased impervious cover. The increased runoff and NPS pollutants cause water quality deterioration in the receiving waters and adversely affect the aqua-ecosystem. These environmental impacts could be reduced through the application of low impact development (LID) techniques. In Korea, more than 80% of the total rainfall occurs in summer and most of these were 10 mm or less. Therefore, if the LIDs developed were able to cope with rainfall of 10 mm and below, NPS management could be efficiently conducted. This research was performed to determine the effect of varying amounts of rainfall on the performance capability of an established infiltration and filtration facility (IF facility) that can be applied to Korea's common rainfall ranges. The IF facility area was 1.75% of the catchment area, however the facility treated more than 40% and 60% runoff volume and pollutant reduction respectively for a 10 mm rainfall. Lastly, higher volume and pollutant reduction could be attained when the LID area was at least 2% of the entire catchment.

• Journal of Korea Water Resources Association
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• v.49 no.4
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• pp.327-333
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• 2016

Due to climate changes accelerated by global warming, South Korea has experienced regional climate variations as well as increasing severities and frequencies of extreme weather. The precipitation in South Korea during the summer season in 2013 was concentrated mainly in the central region; the maximum number of rainy days were recorded in the central region while the southern region had the minimum number of rainy days. As a result, much attention has been paid to the importance of flood control due to damage caused by spatiotemporal intensive rainfalls. In this study, forecast rainfall data was used for rapid responses to prevent disasters during flood seasons. For this purpose, the applicability of numerical weather forecast data was analyzed using the ground observation rainfall and inflow rate. Correlation coefficient, maximum rainfall intensity percent error and total rainfall percent error were used for the quantitative comparison of ground observation rainfall data. In addition, correlation coefficient, Nash-Sutcliffe efficiency coefficient, and standardized RMSE were used for the quantitative comparison of inflow rate. As a result of the simulation, the correlation coefficient up to six hours was 0.7 or higher, indicating a high correlation. Furthermore, the Nash-Sutcliffe efficiency coefficient was positive until six hours, confirming the applicability of forecast rainfall.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.31 no.3B
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• pp.277-284
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• 2011

The limitations of existing Markov chain model for reproducing extreme rainfalls are a known problem, and the problems have increased the uncertainties in establishing water resources plans. Especially, it is very difficult to secure reliability of water resources structures because the design rainfall through the existing Markov chain model are significantly underestimated. In this regard, aims of this study were to develop a new daily rainfall simulation model which is able to reproduce both mean and high order moments such as variance and skewness using a piecewise Kernel-Pareto distribution. The proposed methods were applied to summer and fall season rainfall at three stations in Han river watershed in Korea. The proposed Kernel-Pareto distribution based Markov chain model has been shown to perform well at reproducing most of statistics such as mean, standard deviation and skewness while the existing Gamma distribution based Markov chain model generally fails to reproduce high order moments. It was also confirmed that the proposed model can more effectively reproduce low order moments such as mean and median as well as underlying distribution of daily rainfall series by modeling extreme rainfall separately.