• Atmosphere
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• v.26 no.1
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• pp.111-126
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• 2016

In the numerical weather model, surface properties can be defined by various parameters such as terrain height, landuse, surface albedo, soil moisture, surface emissivity, roughness length and so on. And these parameters need to be improved in the Seoul metropolitan area that established high-rise and complex buildings by urbanization at a recent time. The surface roughness length map is developed from digital elevation model (DEM) and it is implemented to the high-resolution numerical weather (WISE-WRF) model. Simulated results from WISE-WRF model are analyzed the relationship between meteorological variables to changes in the surface roughness length. Friction speed and wind speed are improved with various surface roughness in urban, these variables affected to temperature and relative humidity and hence the surface roughness length will affect to the precipitation and Planetary Boundary Layer (PBL) height. When surface variables by the WISE-WRF model are validated with Automatic Weather System (AWS) observations, NEW experiment is able to simulate more accurate than ORG experiment in temperature and wind speed. Especially, wind speed is overestimated over $2.5m\;s^{-1}$ on some AWS stations in Seoul and surrounding area but it improved with positive correlation and Root Mean Square Error (RMSE) below $2.5m\;s^{-1}$ in whole area. There are close relationship between surface roughness length and wind speed, and the change of surface variables lead to the change of location and duration of precipitation. As a result, the accuracy of WISE-WRF model is improved with the new surface roughness length retrieved from DEM, and its surface roughness length is important role in the high-resolution WISE-WRF model. By the way, the result in this study need various validation from retrieved the surface roughness length to numerical weather model simulations with observation data.

• Journal of Korean Society on Water Environment
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• v.26 no.4
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• pp.654-663
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• 2010

Attention has increasingly focused on the pollutant load discharged from rural area since the enforcement of total maximum daily loads (TMDLs) in korea. As one of the methods to control the inflow of pollutant load during wet weather events, local governments are attempting to apply non-point source control facility. To design those facilities appropriately, it is essential to understand the runoff characteristics of pollutants such as TSS, $BOD_5$, $COD_{Cr}$, TP and TN. In the paper, the quantitative analyses for pollutant runoff characteristics were examined in a small rural watershed with the area of about 53 hectares. For a dry weather day and wet weather events, variation patterns of dry weather flow and runoff characteristics of wet weather flows were monitored and investigated. The runoff model using XP-SWMM reflecting the landuse types of the watershed in detail was simulated to perform the sensitivity analyses for several factors influencing on their hydrograph and pollutographs. As a result, for the case of medium and small rainfall events (i. e. total rainfall of 35.8 and 17.5 mm), the impervious area including green house, roof and road which covers relatively low portion of total area (i. e. 16%) caused substantial first flush and the majority of total runoff load. Therefore, it has been concluded that the runoff characteristics of each pollutant and distribution of impervious area should be considered for the establishment of the control strategy of non-point pollutant runoff at a rural area.

• Journal of Environmental Science International
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• v.17 no.10
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• pp.1183-1193
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• 2008

Today, environmental pollution and destruction due to the industrialization of our modem society have been the global issues. Although now we can lead affluent lives through science technologies and economic development, these environmental problems have resulted in striking the harmonious balance between human beings and nature and threatened human lives with abnormal weather caused by the global warming, destruction of the ozone layer, and El Nino phenomenon, acid rain, decrease in species diversity, movement of hazardous materials, and harmful waste increase. We are aware of the importance of environmental education, but in reality, it seems impossible to implement appropriate environmental education on account of our educational climate which exclusively focuses on the entrance examination. However, environmental education is the most ultimate solution for those problems in that only when students understand our environment fully and grow habits to protect it through environmental education, the present environmental problems can be solved and more serious problems that can be resulted in the future can possibly be prevented. Thus, this study has examined the effect of using image media in the environment subject on students' environmental sensitivity. According to the results, it was shown that it had positive effects on 'sensitivity of environment', 'attitudes towards environment', and 'environmental affinitive behaviors'.

• Atmosphere
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• v.17 no.4
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• pp.349-364
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• 2007

The main purpose of this study is to examine the sensitivity of the WRF (Weather Research and Forecasting) in the wind field to the steepness of mountains in the case with a strong downslope wind occurred in the Yeongdong province. We conducted WRF simulations for February 13 2006. The initial and boundary data are from the NCEP/NCAR $1^{\circ}{\times}1^{\circ}$ GDAS. Arbitrary terrains of the mountains with a symmetric orography and an asymmetric one with steeper leeward slope, were introduced to examine the sensitivity of the shape of the mountains. The simulation with an asymmetric terrain results in stronger maximum surface wind by about $10ms^{-1}$ than with a symmetric terrain, especially in the narrow region from the peak to ~ 4 km away in the downstream. However, the maximum surface wind speed is weaker by $20ms^{-1}$ than with a symmetric terrain away from the narrow peak region. This indicates that the steeper slope leads to the intensification of downslope wind in the narrower region leeward. In addition, for the simulation with an asymmetric terrain, the strength of wave breaking is greater and the Lee wave is more dominant than for that with a symmetric terrain.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.10
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• pp.1791-1795
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• 2007

Small ions generated at conductor corona sources remain in the atmosphere until they recombine with ions of opposite polarity, attach to aerosols, or make contact with an object. Ion current density is major factor to design conductor configuration of DC overhead transmission line. Several techniques have been used to measure the ion current of HVDC overhead transmission line. In this study, the ion current density was measured by a plate electrode made of a metal flat board at DC corona cage. The sensitivity of the plate electrode is $0.156uA/m^2/V$. To obtain an useful database on corona discharge, it is necessary to do corona test on several kinds of conductor bundles. Therefore, a number of experiments were conducted on several kinds of conductor bundles. To reliably analyze ion effects, corona cage test data were obtained over a long period of time under various weather conditions and expressed as a statistical distribution. Ion current density distribution in foul weather shows a significant increase in levels over the corresponding fair weather. Based on this results, we evaluated the environmental characteristic caused by ion flow of three candidated conductor bundles.

• Journal of Digital Convergence
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• v.14 no.8
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• pp.245-252
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• 2016

The purpose of this study is to make up for missing of weather informations from ASOS and AWS using artificial neural networks. We collected temperature, relative humidity and wind velocity for August during 5-yr (2011-2015) and sample designed artificial neural networks, assuming the Seoul weather station was missing. The result of sensitivity study on number of epoch shows that early stopping appeared at 2,000 epochs. Correlation between observation and prediction was higher than 0.6, especially temperature and humidity was higher than 0.9, 0.8 respectively. RMSE decreased gradually and training time increased exponentially with respect to increase of number of epochs. The predictability at 40 epoch was more than 80% effect on of improved results by the time the early stopping. It is expected to make it possible to use more detailed weather information via the rapid missing complemented by quick learning time within 2 seconds.

• Magazine of the Korean Society of Agricultural Engineers
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• v.36 no.3
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• pp.47-59
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• 1994

The irrigation reservoir operation models developed were tested with weather and field data, and the sensitivity of the water requirement deficiency indices(WRDI) were checked with different initial reservoir storages, irrigated areas, and other water uses from the reservoir storage. Seven reservoir release rules were applied to Yongseol Reservoir. Twenty year WRDIs were computed to check performances of those reservoir release rules. Mean WRDIs were 138, 198, 198, 200, 240, 344, and 1033mm for ROM, TOS, COS, CRR, MSC, FAS, and SRC, respectively. The results indicated that ROM contributes consistently to higher operation efficiencies of an irrigation reservoir. The test results of LFROM and SFROM showed that reservoir operation with the proposed optimization technique ROM would be better suited for an irrigation district than those with the other rules. And the proposed model could be used as a tool to improve reservoir operations.

• Atmosphere
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• v.20 no.3
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• pp.287-306
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• 2010

An ensemble Kalman filter (EnKF) with Weather Research and Forecasting (WRF) Model is applied for Typhoon Wukong (200610) to investigate the performance of ensemble forecasts depending on experimental configurations of the EnKF. In addition, the ensemble sensitivity analysis is applied to the forecast and analysis ensembles generated in EnKF, to investigate the possibility of using the ensemble sensitivity analysis as the adaptive observation guidance. Various experimental configurations are tested by changing model error, ensemble size, assimilation time window, covariance relaxation, and covariance localization in EnKF. First of all, experiments using different physical parameterization scheme for each ensemble member show less root mean square error compared to those using single physics for all the forecast ensemble members, which implies that considering the model error is beneficial to get better forecasts. A larger number of ensembles are also beneficial than a smaller number of ensembles. For the assimilation time window, the experiment using less frequent window shows better results than that using more frequent window, which is associated with the availability of observational data in this study. Therefore, incorporating model error, larger ensemble size, and less frequent assimilation window into the EnKF is beneficial to get better prediction of Typhoon Wukong (200610). The covariance relaxation and localization are relatively less beneficial to the forecasts compared to those factors mentioned above. The ensemble sensitivity analysis shows that the sensitive regions for adaptive observations can be determined by the sensitivity of the forecast measure of interest to the initial ensembles. In addition, the sensitivities calculated by the ensemble sensitivity analysis can be explained by dynamical relationships established among wind, temperature, and pressure.

• Journal of the Korean earth science society
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• v.36 no.6
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• pp.567-579
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• 2015

The accurate simulation of micro-scale weather phenomena such as fog using the mesoscale meteorological models is a very complex task. Especially, the uncertainty arisen from initial input data of the numerical models has a decisive effect on the accuracy of numerical models. The data assimilation is required to reduce the uncertainty of initial input data. In this study, the limitation of the mesoscale meteorological model was verified by WRF (Weather Research and Forecasting) model for a summer fog event around the Nakdong river in Korea. The sensitivity analyses of simulation accuracy from the numerical model were conducted using two different initial and boundary conditions: KLAPS (Korea Local Analysis and Prediction System) and LDAPS (Local Data Assimilation and Prediction System) data. In addition, the improvement of numerical model performance by FDDA (Four-Dimensional Data Assimilation) using the observational data from AWS (Automatic Weather System) was investigated. The result of sensitivity analysis showed that the accuracy of simulated air temperature, dew point temperature, and relative humidity with LDAPS data was higher than those of KLAPS, but the accuracy of the wind speed of LDAPS was lower than that of KLAPS. Significant difference was found in case of relative humidity where RMSE (Root Mean Square Error) for LDAPS and KLAPS was 15.7 and 35.6%, respectively. The RMSE for air temperature, wind speed, and relative humidity was improved by approximately $0.3^{\circ}C$, $0.2m\;s^{-1}$, and 2.2%, respectively after incorporating the FDDA.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.65 no.6
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• pp.934-939
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• 2016

This paper made short-term electric load forecasting by using temperature data at three-hour intervals (9am, 12pm, 3pm, and 6pm) provided by the Korea Meteorological Administration (KMA). In addition, the electric power pattern was created using existing electric power data, and temperature sensitivity was derived using temperature and electric power data. We made power load forecasting program using LabVIEW, a graphic language.