• Journal of Korean Society for Atmospheric Environment
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• v.15 no.E
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• pp.73-79
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• 1999

To Characterize the single raindrops as a function of their size we designed the sampling and handling apparatuses. Samplings of single and size- classified raindrops were performed at a height of 20m above the ground level of a Kyoto University building located in Uji, Japan in rain events from middle of July to the end of August, 1999. And PIXE method was applied to the analysis of single raindrops sampled as a function of their size. Diameter change of frozen raindrops by liquid nitrogen did nto affect the size segregation ability of our sampling apparatus. The number of raindrops increases with decreasing drop size. And it is found that the size distribution of raindrops verified depends on the rain events. Application of PIXE analysis to the measurement of single raindrops was very successful. Every element showed a continuous increase in concentration with decreasing raindrop diameter. It seems reasonable to say that our work should be helpful to obtain more detailed information on single raindrops and especially to study on the rainout and washout mechanisms.

• Proceedings of the Korea Water Resources Association Conference
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• 2005.05b
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• pp.1533-1537
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• 2005

The recent rainfall has happened to exceed the design rainfall after 1990 often, due to the characteristic of the rain to be changed. So, it is failing the ability safety of flood defense equipments to exist. This study analyzed the rainfall of Busan in 2003 since 1961 through the FARD2002(Frequency Analysis of Rainfall Duration). The result is equal to the thing which the design rainfall increased a little since 1991. The change of design rainfall created the result to be a flood discharge increase. This study investigated about the impact to influence on the river bank according to the change of flood discharge, the rainfall pattern change as well. This study used the program of HEC-RAS with HEC-HMS and calculated flood discharge with flood level of river. The result is equal to the thing which the computation became a flood level which exceed 50year(River design criteria-Korea water resources association 2002) criteria with 30year(River establishment criteria-Ministry of construction & transportation 1993), because of an area of impermeability increased of model basin.

• Journal of Korean Society for Geospatial Information Science
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• v.25 no.2
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• pp.49-56
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• 2017

In this study, flood analysis was conducted to prepare for damage caused by typhoons and heavy rain due to abnormal climate and climate change. Two - dimensional flooding analysis using the FLUMEN model, which is widely used for national and international flood risk mapping, was conducted for the Nam River Basin, which is the tributary of the Nakdong River. This study divides the topography into $5m{\times}5m$ DEM by ArcView, so that the accuracy of river repair and hydrological characterization and flood area identification can be maximized. As a result of simulation of water flooding, 163.3ha in section 1, 227.7ha in section 2 and 59.9ha in section 3 were simulated.

• Wind and Structures
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• v.23 no.6
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• pp.615-639
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• 2016

Although the underlying mechanism of rain-wind induced vibrations (RWIVs) of stay cables has not been fully understood, some countermeasures have been successfully applied to mitigating this kind of vibration. Among these, installing dampers near the bridge deck was widely adopted, and several field observations have shown its effectiveness. In this study, the effectiveness of dampers to RWIVs of stay cables is numerically investigated comprehensively by means of finite difference method (FDM). Based on the free vibration analysis of a taut string, it is found that the 3-points triangle scheme, which can be easily implemented in FDM, can offer an excellent approximation of the concentrated damping coefficient (expressed as a Dirac delta function) at the location where the damper is installed. Then, free vibration analysis of a 3-D continuous stay cable attached with two dampers is carried out to study the relationship of modal damping ratio and damping coefficient of the dampers. The effects of orientation of the dampers and cable sag on the modal damping ratio are investigated in detail. Finally, the RWIV response of a 3-D continuous stay cable attached with two dampers is examined. The results indicate that 0.5% of damping ratio is sufficient to reduce the RWIV vibration of the Cable A20 on the No.2 Nanjing Bridge over Yangtze River.

• Journal of Astronomy and Space Sciences
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• v.31 no.4
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• pp.325-333
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• 2014

We are motivated by both the accumulating evidence for the connection of solar variability to the chemistry of nitrogen oxide in the atmosphere and recent finding that the Galactic cosmic-ray (GCR) influx is associated with the solar north-south asymmetry. We have analyzed the measured pH in precipitation over the 109 stations distributed in the United States. We have found that data of pH in precipitation as a whole appear to be marginally anti-correlated with the solar asymmetry. That is, rain seems to become less acidic when the southern hemisphere of the Sun is more active. The acidity of rain is also found to be correlated with the atmospheric temperature, while not to be correlated with solar activity itself. We have carried on the analysis with two subsamples in which stations located in the east and in the west. We find that the pH data derived from the eastern stations which are possibly polluted by sulfur oxides and nitrogen oxides are not correlated with the solar asymmetry, but with the temperature. On the contrary, the pH data obtained from the western stations are found to be marginally anti-correlated with the solar asymmetry. In addition, the pH data obtained from the western stations are found to be correlated with the solar UV radiation. We conclude by briefly pointing out that a role of the solar asymmetry in the process of acidification of rain is to be further examined particularly when the level of pollution by sulfur oxides and nitrogen oxides is low.

• Journal of the Korean Data and Information Science Society
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• v.28 no.3
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• pp.483-492
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• 2017

Precipitation is one of key components in hydrological modeling and water balance studies. A comprehensive, optimized and sustainable water balance monitoring requires the availability of accurate precipitation data. The amount of precipitation measured in a gauge is less than the actual precipitation reaching the ground. The objective of this study is to determine the wind-induced under-catch of solid precipitation and develop a continuous adjustment function for measurements of all types of winter precipitation (from rain to dry snow), which can be used for operational measurements based on data available at standard automatic weather stations. This study provides Bayesian analysis for the systematic structure of catch ratio in precipitation measurement.

• Journal of Environmental Science International
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• v.29 no.9
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• pp.871-883
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• 2020

Due to recent heavy rain events, there are increasing demands for adapting infrastructure design, including drainage facilities in urban basins. Therefore, a clear definition of urban rainfall must be provided; however, currently, such a definition is unavailable. In this study, urban rainfall is defined as a rainfall event that has the potential to cause water-related disasters such as floods and landslides in urban areas. Moreover, based on design rainfall, these disasters are defined as those that causes excess design flooding due to certain rainfall events. These heavy rain scenarios require that the design of various urban rainfall facilities consider design rainfall in the target years of their life cycle, for disaster prevention. The average frequency of heavy rain in each region, inland and coastal areas, was analyzed through a frequency analysis of the highest annual rainfall in the past year. The potential change in future rainfall intensity changes the service level of the infrastructure related to hand-to-hand construction; therefore, the target year and design rainfall considering the climate change premium were presented. Finally, the change in dimensional safety according to the RCP8.5 climate change scenario was predicted.

• Atmosphere
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• v.26 no.2
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• pp.321-336
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• 2016

Damages caused by torrential rain occur every year in Korea and summer time convection can cause strong thunderstorms to develop which bring dangerous weather such as torrential rain, gusts, and flash flooding. On 6 August 2013 a sudden torrential rain concentrated over the inland of Southern Korean Peninsula occurred. This was an event characterized as a mesoscale multicellular convection. The purpose of this study is to analyze the conditions of the multicellular convection and the synoptic and mesoscale nature of the system development. To this end, dynamical and thermodynamic analyses of surface and upper-level weather charts, satellite images, soundings, reanalysis data and WRF model simulations are performed. At the beginning stage there was a cool, dry air intrusion in the upper-level of the Korean Peninsula, and a warm humid air flow from the southwest in the lower-level creating atmospheric instability. This produced a single cell cumulonimbus cloud in the vicinity of Baengnyeongdo, and due to baroclinic instability, shear and cyclonic vorticity the cloud further developed into a multicellular convection. The cloud system moved southeast towards Seoul metropolitan area accompanied by lightning, heavy precipitation and strong wind gusts. In addition, atmospheric instability due to daytime insolation caused new convective cells to develop in the upstream part of the Sobaek Mountain which merged with existing multicellular convection creating a larger system. This case was unusual because the system was affected little by the upper-level jet stream which is typical in Korea. The development and propagation of the multicellular convection showed strong mesoscale characteristics and was not governed by large synoptic-scale dynamics. In particular, the system moved southeast crossing the Peninsula diagonally from northwest to southeast and did not follow the upper-level westerly pattern. The analysis result shows that the movement of the system can be determined by the vertical wind shear.

• Journal of the Korean Institute of Intelligent Systems
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• v.18 no.3
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• pp.297-305
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• 2008

Recently, kernel methods have attracted great interests in the areas of pattern classification, function approximation, and anomaly detection. The role of the kernel is particularly important in the methods such as SVM(support vector machine) and KPCA(kernel principal component analysis), for it can generalize the conventional linear machines to be capable of efficiently handling nonlinearities. This paper considers the problem of combining radar and rain gauge observations utilizing the regression approach based on the kernel-based gaussian process and support vector learning. The data-assimilation results of the considered methods are reported for the radar and rain gauge observations collected over the region covering parts of Gangwon, Kyungbuk, and Chungbuk provinces of Korea, along with performance comparison.

• Journal of the Society of Disaster Information
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• v.14 no.4
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• pp.421-429
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• 2018

Purpose: This study conducted a slope stability study considering changes in the ground water level due to rain phenomena and the duration of rainfall, that is for the purpose of analyzing the stability of the slope surface of the cut section, seepage numerical analysis is performed by height of slope and rainfall accident, and the characteristics of rainfall was applied reasonably in order to determine the slope change during rain by analyzing rainfall and rainfall pattern due to climate change. Results: As a result of numerical analysis of stability for slope composed of the granite weathered soils according to the characteristics of rainfall(Uniform Rainfall, US Army Corps., Huff's method - 1/4, 4/4), Conclusion: The higher the slope, the smaller the safety factor of the slope, the smaller the elevation of the ground water level as the rainwater seepage does not reach the underground water level. In addition, the ground water level was assessed to be rose significantly in condition of case 3 Huff's method - 1/4, rain pattern with the largest initial rainfall duration, and the safety factor was analyzed to be small.