• Journal of Korea Water Resources Association
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• v.48 no.1
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• pp.37-44
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• 2015

A Bayesian nonstationary probability rainfall estimation model using the Grid method is developed. A hierarchical Bayesian framework is consisted with prior and hyper-prior distributions associated with parameters of the Gumbel distribution which is selected for rainfall extreme data. In this study, the Grid method is adopted instead of the Matropolis Hastings algorithm for random number generation since it has advantage that it can provide a thorough sampling of parameter space. This method is good for situations where the best-fit parameter values are not easily inferred a priori, and where there is a high probability of false minima. The developed model was applied to estimated target year probability rainfall using hourly rainfall data of Seoul station from 1973 to 2012. Results demonstrated that the target year estimate using nonstationary assumption is about 5~8% larger than the estimate using stationary assumption.

• Journal of the Korean GEO-environmental Society
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• v.16 no.3
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• pp.49-55
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• 2015

The rainfall pattern, rainfall intensity as well as topographical conditions used for the analysis of debris flow affect, in general, the magnitude of debris flow and flow velocity, when debris flow occurs. The consideration of topographical conditions implies that the topography is equally divided into grids and the slope of inside the grid is computed as an average, leading to, in turn, obtain the closer results to the reality as the grid is smaller in the case of the severely bended topography. Although the size of grid should be as small as possible so as for more accurate analysis of debris flow, the analysis of debris flow has been so far conducted by using sparsely divided grids due to the limitation of analysis algorithm, computational ability and running time. So, it is necessary to suggest an appropriate grid size for the practical approaches. Therefore, this study presents the evaluation of the effect of the size of a grid on the debris flow besides the factors which referred to the previous studies such as accumulated rainfall, rainfall intensity and rainfall duration time. From this, it enables to suggest a rational and practical grid size for topography to be divided.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.5
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• pp.3-15
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• 2006

The purpose of the study is to determine grid cell of radar relationship, and to promote the radar data on hydrology field. The study region is the Chungjudam basin with a drainage area of $6,648km^{2}$ located within the 260 km circle under the DWSR-88C C-band umbrella(Kwanak Mt Radar). Grid cell was produced to extract radar reflectivity and rainfall data of the same time and point using Arc-view software package. The grid cell size is to estimate mean correlation coefficient for $1km{\times}1km,\;2km{\times}2km,\;3km{\times}3km$ grid. The result of mean correlation coefficient showed good result(0.57) for the $1km{\times}1km$ grid cell. The 32 rainfall stations Z-R relationship was estimated in Chungjudam basin.

• Journal of The Korean Society of Agricultural Engineers
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• v.65 no.3
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• pp.69-82
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• 2023

Representative meteorological data of the rural water district, which is the spatial unit of the study, was produced using the grid-based national standard RCP scenario rainfall data provided by the Korea Meteorological Administration. The retrospective reproducibility of the climate model scenario data was analyzed, and the change in climate characteristics in the water district unit for the future period was presented. Finally the data characteristics and differences of each meteorological element according to various spatial resolution conversion and post-processing methods were examined. As a main result, overall, the distribution of average precipitation and R95p of the grid data, has reasonable reproducibility compared to the ASOS observation, but the maximum daily rainfall tends to be distributed low nationwide. The number of rainfall days tends to be higher than the station-based observation, and this is because the grid data is generally calculated using the area average concept of representative rainfall data for each grid. In addition, in the case of coastal regions, there is a problem that administrative districts of islands and rural water districts do not match. and In the case of water districts that include mountainous areas, such as Jeju, there was a large difference in the results depending on whether or not high rainfall in the mountainous areas was reflected. The results of this study are expected to be used as foundation for selecting data processing methods when constructing future meteorological data for rural water districts for future agricutural water management plans and climate change vulnerability assessments.

• Atmosphere
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• v.21 no.4
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• pp.391-404
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• 2011

This study investigates the impact of cumulus parameterization scheme (CPS) with different horizontal grid sizes on the simulation of the local heavy rainfall case over the Korean Peninsula. The Weather Research and Forecasting (WRF)-based real-time forecast system of the Joint Center for High-impact Weather and Climate Research (JHWC) is used. Three CPSs are used for sensitivity experiments: the BMJ (Betts-Miller-Janjic), GD (Grell-Devenyi ensemble), and KF (Kain-Fritsch) CPSs. The heavy rainfall case selected in this study is characterized by low-level jet and low-level transport of warm and moist air. In 27-km simulations (DM1), simulated precipitation is overestimated in the experiment with BMJ scheme, and it is underestimated with GD scheme. The experiment with KF scheme shows well-developed precipitation cells in the southern and the central region of the Korean Peninsula, which are similar to the observations. All schemes show wet bias and cold bias in the lower troposphere. The simulated rainfall in 27-km horizontal resolution has influence on rainfall forecast in 9-km horizontal resolution, so the statements on 27-km horizontal resolution can be applied to 9-km horizontal resolution. In the sensitivity experiments of CPS for DM3 (3-km resolution), the experiment with BMJ scheme shows better heavy rainfall forecast than the other experiments. The experiments with CPS in 3-km horizontal resolution improve rainfall forecasts compared to the experiments without CPS, especially in rainfall distribution. The experiments with CPS show lower LCL(Lifted Condensation Level) than those without CPS at the maximum rainfall point, and weaker vertical velocity is simulated in the experiments with CPS compared to the experiments without CPS. It means that CPS suppresses convective instability and influences mainly convective rainfall. Consequently, heavy rainfall simulation with BMJ CPS is better than the other CPSs, and even in 3-km horizontal resolution, CPS should be applied to control convective instability. This conclusion can be generalized by conducting more experiments for a variety of cases over the Korean Peninsula.

• Journal of Wetlands Research
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• v.13 no.1
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• pp.105-116
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• 2011

Changes in climate have largely increased concentrated heavy rainfall, which in turn is causing enormous damages to humans and properties. Therefore, the exact relationship and the spatial variability analysis of hydrometeorological elements and characteristic factors is critical elements to reduce the uncertainty in rainfall -runoff model. In this study, radar rainfall grid resolution and grid resolution depending on the topographic factor in rainfall - runoff models were how to respond. In this study, semi-distribution of rainfall-runoff model using the model ModClark of Inje, Gangwon Naerin watershed was used as Gwangdeok RADAR data. The completed ModClark model was calibrated for use DEM of cell size of 30m, 150m, 250m, 350m was chosen for the application, and runoff simulated by the RADAR rainfall data of 500m, 1km, 2km, 5km, 10km from 14 to 17 on July, 2006. According to the resolution of each grid, in order to compare simulation results, the runoff hydrograph has been made and the runoff has also been simulated. As a result, it was highly runoff simulation if the cell size is DEM 30m~150m, RADAR rainfall 500m~2km for peak flow and runoff volume. In the statistical analysis results, if every DEM cell size are 500m and if RADAR rainfall cell size is 30m, relevance of model was higher. Result of sensitivity assessment, high index DEM give effect to result of distributed model. Recently, rainfall -runoff analysis is used lumped model to distributed model. So, this study is expected to make use of the efficiently decision criteria for configurated models.

• Journal of Korea Water Resources Association
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• v.37 no.3
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• pp.233-240
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• 2004

Most of hydrological analyses in the field of water resources are launched by gathering and analyzing rainfall data. Several methods have been developed to estimate areal rainfall from point rainfall data and to fill missing or ungaged data. Thiessen and Reciprocal Distance Squared(RDS) methods whose parameters are only dependent on inter-station distance are classical work in hydrology, but these techniques do not provide a continuous representation of the hydrologic process involved. In this study, kriging technique was applied to rainfall analysis in Nakdong river basin in order to complement the defects of these classical methods and to reflect spatial characteristics of regional rainfall. After spatial correlation and semi-variogram analyses were performed to perceive regional rainfall property, kriging analysis was performed to interpolate rainfall data for each grid Thus, these procedures were enable to estimate average rainfall of subbasins. In addition, poor region of rainfall observation was analyzed by spatial interpolation error for each grid and mean error for each subbasin.

• Atmosphere
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• v.16 no.4
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• pp.319-332
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• 2006

This study examines the capability of the WRF (Weather Research and Forecasting) model in reproducing heavy rainfall that developed over the Korean peninsula on 26-27 June 2005. The model is configured with a triple nesting with the highest horizontal resolution at a 3-km grid, centered at Yang-dong, Gyeonggi-province, which recorded the rainfall amount of 376 mm. In addition to the control experiment employing realistic orography over Korea, two consequent sensitivity experiments with 1) no orography, and 2) no land over Korea were designed to investigate orographic effects on the development of heavy rainfall. The model was integrated for 48 hr, starting at 1200 UTC 25 June 2005. The overall features of the large-scale patterns including a cyclone associated with the heavy rainfall are reasonably reproduced by the control run. The spatial distribution of the simulated rainfall over Korea agreed fairly well with the observed. The amount of predicted maximum rainfall at the 3-km grid is 377 mm, which located about 50 km southeast from the observed point, Yang-Dong, indicating that the WRF model is capable of predicting heavy rainfall over Korea at the cloud resolving resolutions. Further, it was found that the complex orography over the Korean peninsula plays a role in enhancing the rainfall intensity by about 10%. The land-sea contrast over the peninsula was fund to be responsible for additional 10% increase of rainfall amount.

• Journal of Korea Water Resources Association
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• v.41 no.11
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• pp.1123-1133
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• 2008

It needs to conceptualize watershed with triangular or rectangular elements and to analyze the changes in hydrological components of each element for distributed modeling of rainfall-runoff process. This study is the network analysis of watershed grid for flow routing occurred in each element when analyzing rainfall-runoff process by one-dimensional kinematic wave equation. Single flow direction from D8-method(deterministic eight-neighbors method) is used, and the information of flow direction and flow accumulation are used to determine the computation order of each element. The application theory of finite volume method is suggested for each flow direction pattern between elements, and it is applied it to calculate the flow of each grid. Network analysis method from this study is applied to GRM(Grid based Rainfall-runoff Model) which is physically based distributed rainfall-runoff model, and the results from simplified hypothetical watersheds are compared with $Vflo^{TM}$ to examine the reasonability of the method. It is applied to Jungrangcheon watershed in Han river for verification, and examination of the applicability to real site. The results from Jungrangcheon watershed show good agreement with measured hydrographs, and the application of the network analysis method to real site is proper.

• Journal of Korea Water Resources Association
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• v.41 no.9
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• pp.895-905
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• 2008

To analyze hydrologic processes in a watershed requires both various geographical data and hydrological time series data. Recently, not only geographical data such as DEM(Digital Elevation Model) and hydrologic thematic map but also hydrological time series from numerical weather prediction and rainfall radar have been provided as grid data, and there are studies on hydrologic analysis using these grid data. In this study, GRM(Grid based Rainfall-runoff Model) which is physically-based distributed rainfall-runoff model has been developed to simulate short term rainfall-runoff process effectively using these grid data. Kinematic wave equation is used to simulate overland flow and channel flow, and Green-Ampt model is used to simulate infiltration process. Governing equation is discretized by finite volume method. TDMA(TriDiagonal Matrix Algorithm) is applied to solve systems of linear equations, and Newton-Raphson iteration method is applied to solve non-linear term. Developed model was applied to simplified hypothetical watersheds to examine model reasonability with the results from $Vflo^{TM}$. It was applied to Wicheon watershed for verification, and the applicability to real site was examined, and simulation results showed good agreement with measured hydrographs.