• Journal of Korean Society for Atmospheric Environment
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• v.34 no.1
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• pp.177-186
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• 2018

It is a well-known fact that precipitation plays an important role in capturing ambient particles, however, the details of particle scavenging properties have not been fully proved. To clarify the particle scavenging properties, a complementary study was carried out with the bulk and semi-bulk rain samples collected in an urban city of Japan. pH showed a continued downturn for a little bit at the beginning rainfall and then a turn-up in the following rainfall. The recorded pH values of rainwater (ranged from 3.5-4.6) demonstrated that the strong acid rain was observed during our field measurements. Compared to the subsequent rainfall, electrical conductivity in the beginning rainfall had about 1.3 times higher level. Sulfur showed an overwhelmingly high concentration compared to other elements in both ambient total suspended particles (TSP) and rain samples. On the contrary to ambient TSP, every element including Ca and Zn in rain showed a continued rise in concentration accompanied by increasing of rainfall amount. During the first period of the rainfall there was no meaningful change in elemental carbon concentration, however, it was largely increased (up to $0.2mg\;L^{-1}$) in the sequential rainfall (4.0-4.5 mm rainfall amount). The theoretically calculated number concentration of particles scavenged by raindrops showed a strong decrease of with the increasing droplet diameter regardless of particle type.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.1
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• pp.63-72
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• 1994

The objective of the study is to develop weather generators for daily rainfall and small pan evaporation and to test the applicability with recorded data. Daily rainfall forecasting model(DRFM) was developed that uses a first order Markov chain to describe rainfall seque- nces and applies an incomplete Gamma function to predict the amount of precipitation. Daily evaporation forecasting model(DEFM) that adopts a normal distribution function to generate the evaporation for dry and wet days was also formulated. DRFM and DEFM were tested with twenty year weather data from eleven stations using Chi-square and Kolmogorov and Smirnov goodness of fit tests. The test results showed that the generated sequences of rainfall occurrence, amount of rainfall, and pan evaporation were statistically fit to recorded data from eleven, seven, and seven stations at the 5% level of significance. Generated rainfall data from DRFM were very close in frequency distri- bution patterns to records for stations all over the country. Pan evaporation for rainy days generated were less accurate than that for dry days. And the proposed models may be used as tools to provide many mathematical models with long-term daily rainfall and small pan evaporation data. An example is an irrigation scheduling model, which will be further detailed in the paper.

• Korean Journal of Soil Science and Fertilizer
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• v.44 no.6
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• pp.1004-1009
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• 2011

Soil erosion in North Korea has been continued to accelerate by deterioration of topographical conditions. However, few studies have been conducted to predict the amount of soil loss in North Korea due to limited data so far. Rainfall erosivity is an important factor to predict the amount of long-term annual soil loss by USLE (universal soil loss equation). The purpose of this study is to investigate rainfall erosivity, which presented the potential risk of soil erosion by water, in North Korea. Annual rainfall erosivities for 27 stations in North Korea for 1983~2010 were calculated using regression models based on modified Institute of Agricultural Sciences (IAS) index in this study. The result showed that annual average rainfall erosivity in North Korea ranged from 2,249 to 7,526 and averaged value was $4,947MJmm\;ha^{-1}\;hr^{-1}\;yr^{-1}$, which corresponded to about 70% of annual average rainfall erosivity in South Korea. The finding was that the potential risk of soil erosion in North Korea has been accelerated by the increase of rainfall erosivity since the late 1990s.

• Proceedings of the KSR Conference
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• 2003.10b
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• pp.397-402
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• 2003

Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the rainfall and stability of railway embankment are defined to analyze the stability of embankment by rainfall. An experimental study for defining of infiltration rate of rainfall into slope is conducted in the lab. The results of Rainfall infiltration show that rainfall infiltration is not equal to infiltration as like reservoir because rate of rainfall infiltration is controlled by slope angle. Based on these results, boundary condition of rainfall is altered and various numerical analysis are performed. The variation of shear strength, the degree of saturation and pore-water pressure for railway slope during rainfall can be predicted and the safety factor of railway slope can be expressed as the function of rainfall amount, namely rainfall index. Therefore, it is judged that this rainfall index can be a good tool for the rail-transport operation control.

• Proceedings of the Korean Association of Geographic Inforamtion Studies Conference
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• 2009.04a
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• pp.269-270
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• 2009

This study builds a sediment rating curve using the measured sediment yield and the simulated soil erosion by a GIS-embedded empirical model. Then the structured sediment rating curve is used to determine the SDR on a basin scale in southern Korea. The whole data(year of 2002-2008) are divided into two groups and the first group(year of 2002-2005) is used for calibration, while the other is used for validation. Two cases(rainfall amount and rainfall intensity) are analyzed to consider the rainfall runoff erosivity factor in simulating soil erosion. The results show the derived SDR provides reasonable accuracy and rainfall intensity gives better performance in calculating soil erosion than rainfall amount.

• Atmosphere
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• v.26 no.1
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• pp.141-158
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• 2016

The objective of this study is to examine the impact of urban canopy and the horizontal resolution on simulated meteorological variables such as 10-m wind speed, 2-m temperature and precipitation using WRF model for a local, convective rainfall case. We performed four sensitivity tests by varying the use of urban canopy model (UCM) and the horizontal resolution, then compared the model results with observations of AWS network. The focus of our study is over the Seoul metropolitan area for a convective rainfall that occurred on 16 August 16 2015. The analysis shows that mean diurnal variation of temperature is better simulated by the model runs with UCM before the convective rainfall. However, after rainfall, model shows significant difference in air temperature among sensitivity tests depending on the simulated rainfall amount. The rainfall amount is significantly underestimated in 0.5 km resolution model run compared to 1.5 km resolution, particularly over the urban areas. This is due to earlier occurrence of light rainfall in 0.5 km resolution model. Earlier light rainfall in the afternoon eliminates convective instability significantly, which prevents occurrence of rainfall later in the evening. The use of UCM results in a higher maximum rainfall in the domain, which is due to higher temperature in model runs with urban canopy. Earlier occurrence of rainfall in 0.5 km resolution model is related to rapid growth of PBL. Enhanced mixing and higher temperature result in rapid growth of PBL, which provides more favorable conditions for convection in the 0.5 km resolution run with urban canopy. All sensitivity tests show dry bias, which also contributes to the occurrence of light precipitation throughout the simulation period.

• Journal of Wetlands Research
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• v.15 no.2
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• pp.233-250
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• 2013

Gradually or radically change how the characteristics of the climate characteristic using change point analysis for the precipitation indicators were investigated. Significantly the amount, extreme and frequency were separated by precipitation indicators, each indicator RIA(Rainfall Index for Amount), RIE(Rainfall Index for Extremes) and RIF(Rainfall Index for Frequency) was defined. Bayesian Change Point was applied to investigate changing over time of precipitation indicators calculated. As the result of analysis, precipitation indicators in South Korea was found to recently increase all indicators except for the annual precipitation days and 200-yr precipitation. RIA revealed that there was a very clear point of significance for the change in Ulleungdo, Relatively significant results for RIE were identified in Gumi, Jecheon and Seogwipo. Also, since the 1990s, an increase in the number of variation points, and the horizontal width of the fluctuation point was being relatively wider. Based on these results, rethink the precipitation on the assumption of stationarity was judged necessary.

• Proceedings of the KSR Conference
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• 2002.10a
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• pp.601-607
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• 2002

Infiltration of rainfall causes railway embankment to be unstable and may result in failure. Basic relationship between the stability of railway embankment and rainfall introducing the partial saturation concept of ground are defined to analyze the stability of embankment by rainfall. A pressure plate test is also peformed to obtain soil-water characteristic curve of unsaturated soils. Based on this curve, the variables in the shear strength function and permeability function are also defined. These functions are used fur the numerical model for evaluation of railway embankments under rainfall. As comparing the model and case studies, the variation of shear strength, the degree of saturation and pore-water pressure for railway embankment during rainfall can be predicted and the safety factor of railway embankment can be expressed as the function of rainfall amount namely rainfall index. Therefore, the research on safety factor on railway embankment considering train speed and rainfall infiltration with the variation of rainfall intensity and rainfall duration was carried out in this paper.

• Journal of Korea Water Resources Association
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• v.51 no.9
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• pp.783-793
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• 2018

The purpose of this study to present updated regional annual mean rainfall erosivity data in the Republic of Korea. In 2012, Ministry of Environment in Korea published the notice about investigation and survey procedure for the amount of topsoil erosion and adopted USLE (Universal Soil Loss Equation) model to predict the amount of national-scale soil erosion in Korea. In the notice, regional rainfall erosivity values for 158 sites, which is essential to apply the USLE, were included, however, these values came from the data made before 1997 and need to be updated. This study collected, classified and combined annual mean rainfall erosivity data from the literature review to analyze the data. We presented that new iso-erodent map, interpolated by IDW (Inverse Distance Weighted) method and extracted updated regional annual mean rainfall erosivity data at 167 regions for 1961~2015. These values will be used as updated rainfall erosivity data to predict the amount of topsoil erosion in Korea.

• Journal of Environmental Science International
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• v.8 no.4
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• pp.419-422
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• 1999

A new method is developed to measure rainfall with high accuracy and resolution. The principle of new method is to detect a weight change of a buoyant weight according to a change in water level of raingage measured by the use of a strain-gage load cell. Field test of the method was carried out on 30 September 1998, when there was heavy rainfall with total amount of 189.60mm. The results are as follows; 1) In spite of heavy rainfall, this new method showed the total error of only 1.5% against the total amount of 189.60mm. 2) This new mechanism accomplished high accuracy and resolution at filed test in heavy rainy day. 3) The present study provided a possibility to develop a new raingage with an 0.01mm in rainfall measurement.