Soon-Hwan Lee

Impact of Meteorological Wind Fields Average on Predicting Volcanic Tephra Dispersion of Mt. Baekdu

In order to clarify the advection and dispersion characteristics of volcanic tephra to be emitted from the Mt. Baekdu, several numerical experiments were carried out using three-dimensional atmospheric dynamic model, Weather and Research Forecast (WRF) and Laglangian particles dispersion model FLEXPART. Four different temporally averaged meteorological values including wind speed and direction were used, and their averaged intervals of meteorological values are 1 month, 10 days, and 3days, respectively. Real time simulation without temporal averaging is also established in this study. As averaging time of meteorological elements is longer, wind along the principle direction is stronger. On the other hands, the tangential direction wind tends to be clearer when the time become shorten. Similar tendency was shown in the distribution of volcanic tephra because the dispersion of particles floating in the atmosphere is strongly associated with wind pattern. Wind transporting the volcanic tephra is divided clearly into upper and lower region and almost ash arriving the Korean Peninsula is released under 2 km high above the ground. Since setting up the temporal averaging of meteorological values is one of the critical factors to determine the density of tephra in the air and their surface deposition, reasonable time for averaging meteorological values should be established before the numerical dispersion assessment of volcanic tephra.

Impacts of the High-Resolution Sea Surface Temperature Distribution on Modeled Snowfall Formation over the Yellow Sea during a Cold-Air Outbreak

AbstractHigh-resolution sea surface temperature (SST) products and idealized SST distributions were used to simulate snowfall over the Yellow Sea during 30–31 December 2007 using the Weather Research and Forecasting Model (WRF). Large differences were found between the SST distributions in the New Generation Sea Surface Temperature (NGSST) and Operational Sea Surface Temperature and Sea Ice Analysis (OSTIA) datasets near the Yellow Sea coast. Idealized SST datasets were defined to examine the influence of this difference in detail. The SST differences influenced the cloud streets and resultant snowfall formation. In simulations with the idealized SST distributions, convection developed and intensified later when the SST gradient was increased. In addition, the intensity of cloud streets was enhanced along the center of the flow. The simulations using the NGSST dataset showed widely distributed cloud streets and snowfall and heavier snowfall over the western Korean Peninsula, while those using the OSTIA da...

Development of Integrated Process Planning and Monitoring System for Turning Operation

Summary This paper deals with the development of a prototype system which integrates process planning interfaced with CAD system and process monitoring for CNC turning operation through the interlace and integration of data and knowledge processing. The integrated system is aimed for small and medium-sized machinery industry, and AutoCAD and CLPS which can be run on personal computer are used as a CAD system and an expert system shell for knowledge-based process planning, respectively. The test results to show the system performance indicate that this prototype system works well for turning operation.

A Case Analysis of Volcanic Ash Dispersion under Various Volcanic Explosivity Index of the Mt. Baegdu

In order to clarify the characteristics of dispersion of volcanic tephra emitted from the Mt. Baegdu with various eruption environment, numerical analysis were performed using numerical models, Weather Research and Forecast (WRF) and FLEXPART. Synoptic conditions at 12 October 2010 was adopted because the volcanic ash of Mt. Baegdu can reach the Korean peninsula and its dispersion pattern was compared with different Volcanic Explosivity Index (VEI) and particle size. Predominant size of falling out ash flowing in the peninsular is smaller than 0.5 mm and the ash large than the size is difficult to get in the peninsular due to the its weak ability of truculent diffusion. the difference of ash distribution with various VEI scenarios is not so much but number density of ash in the air is dramatically changed. Volcanic ash tends to be deposited easily in eastern coastal area such as Gangneung and Busan, because of the inflow of ash from East Sea and barrier effect of the Taeback mountains along the east coast of the Korean Peninsula. Accumulated amount of ash deposition can be increased in short period in several urban areas.

Numerical Study on the Impact of the Spatial Resolution of Wind Map in the Korean Peninsula on the Accuracy of Wind Energy Resources Estimation

In order to make sure the impact of spatial resolution of wind energy map on the estimation of wind power density in the Korean Peninsula, the comparison studies on the characteristics of wind energy map with three different spatial resolutions were carried out. Numerical model used in the establishment of wind map is MM5 (5th generation Mesoscale Model) with RBAPS (Regional Data Assimilation and Prediction System) as initial and boundary data. Analyzed Period are four months (March, August, October, and December), which are representative of four seasons. Since high spatial resolution of wind map make the undulation of topography be clear, wind pattern in high resolution wind map is correspond well with topography pattern and maximum value of wind speed is also increase. Indication of island and mountains in wind energy map depends on the its spatial resolution, so wind patterns in Heuksan island and Jiri mountains are clearly different in high and low resolutions. And area averaged power density can be changed by estimation method of wind speed for unit area in the numerical model and by treatment of air density. Therefore the studiable resolution for the topography should be evaluated and set before the estimation of wind resources in the Korean Peninsula.

Influence of continuous satellite-based SST distribution on heavy snowfall events over the Korean Peninsula

To understand the mechanism for the development of heavy snowfall and the influence of the variation in the satellite-based Sea Surface Temperature (SST) distribution on the evolution of snow convection cells, synoptic characteristics of heavy snowfall over the Honam District, south-western Korean Peninsula, were analysed during December 2005; several numerical experiments were also conducted. New Generation Sea Surface Temperature (NGSST) data based on satellite observation are used in this study, with Penn State University/National Center for Atmospheric Research (PSU/NCAR) 5th- generation Mesoscale Model (MM5) used as the numerical model. Since the cold air from the arctic centre spreads strongly along the planetary wave, the Siberian high pressure matured earlier than normal in 2005. The analysis of the Arctic Oscillation Index (AOI) also indicated the development of a cold Siberian high. Snow convection cells occurred primarily as a result of air–sea interactions and orographic forcing over the Korean Peninsula and, in this case, two major convection cells appeared on 21 December 2005. Because of the decrease in the SST with time, the intensity of the convection cells also decreased with time. The two-dimensional distribution of the SST was also strongly associated with the amount of inland snowfall. Therefore, satellite-based observation is a useful method to detect the change in detail of SST distribution, and the exact estimation of the SST gradient in the central Yellow Sea and near the coast is also an important factor in forecasting the intensity of snowfall over the south-western Korean Peninsula.

Spatial and Temporal Features of PM 10 Evolution Cycle in the Korean Peninsula

【Power spectral analysis for

Characteristics of sea breeze front development with various synoptic conditions and its impact on lower troposphere ozone formation

PM_{10}

Comparison Study on the Estimation Algorithm of Land Surface Temperature for MODIS Data at the Korean Peninsula

observed at 10 cities in the Korean Peninsula from 2004 to 2010 was carried out to examine the spatial and temporal features of

Impact of the Variation of Sea Breeze Penetration due to Terrain Complexity on PBL Development

PM_{10}