• Journal of Korean Society for Atmospheric Environment
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• v.25 no.1
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• pp.57-74
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• 2009

In order to clarify the vertical ozone distribution in planetary boundary layer of coastal area with complex terrain, an observation campaign was carried out around Gwangyang Bay with dense pollutant emission sources during two days from June, 4 2007. For this observation are Radiosonde, SODAR(SOnic Detection And Ranging) and Tethered ozone sonde were employed. The surface meteorological and photochemical observation data provided by AWS (Automatic Weather System) and AQMS (Air Quality Monitoring System) were also applied for analysis. Synoptic condition is strongly associated with lower level ozone distribution in complex terrain coastal area. Since mesoscale circulation induced by difference of characteristics of land and sea and orographic forcing is predominant under calm synoptic condition, vertical distribution of ozone is complicate and vertical ozone concentration greatly fluctuated. However in second day when synoptic influence become strong, ozone concentration in lower levels is vertically uniform regardless of observation level. This results in vertical observation indicates that vertical ozone distribution is often determined by synoptic condition and also affects surface ozone concentration.

• Journal of the Korean Solar Energy Society
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• v.30 no.4
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• pp.79-85
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• 2010

The uncertainty in WindCube LIDAR measurements, which are specific to wind profiling at less than 200m above ground levelin wind resource assessments, was analyzed focusing on the error caused by its volume sampling principle. A two-month SODAR measurement campaign conducted in an urban environment was adopted as the reference wind profile assuming that various atmospheric boundary layer shapes had been captured. The measurement error of LIDAR at a height z was defined as the difference in the wind speeds between the SODAR reference data, which was assumed to be a virtually true value, and the numerically averaged wind speed for a sampling volume height interval of $z{\pm}12.5m$. The pattern of uncertainty in the measurement was found to have a maximum in the lower part of the atmospheric boundary layer and decreased with increasing height. It was also found that the relative standard deviations of the wind speed error ratios were 6.98, 2.70 and 1.12% at the heights of 50, 100 and 150m above ground level, respectively.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.25 no.10
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• pp.1427-1435
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• 2001

Air movement in wokplaces, whether resulting from a forced ventilation system or naturally occurring airflow, has a significant impact on occupational health. In a huge shipbuilding factory building, typical harmful factors such as fume or vaporized gas from welding and cutting of steel plates, and dusts from grinding give unpleasant feeling. From field data survey, the yearly dominant, wind directions for the shipbuilding factory building tested were northwest, northeast and southeast Among the three wind directions, the ventilation improvement was the worst for the northeastern wind. This study was focused on location of the opening vents in order to utilize the natural ventilation effectively. Instantaneous velocity fields inside the 1/1000 scale-down factory building model were measured using a 2-frame PIV system. The factory building model was embedded in an atmospheric boundary layer simulated in a wind tunnel. The modified vents improve the internal Ventilation flow with increasing the flow speed more than two times, compared with that of present vents.

• Journal of Korean Society for Atmospheric Environment
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• v.27 no.4
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• pp.416-425
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• 2011

To analyze the physical processes of sea-breeze development over a coastal urban area, numerical simulation for seabreeze (SB) and its frontogenesis was examined based on urbanized MM5 (uMM5) with urban canopy parameterization. On 6 August 2006, SB and its front were well developed in Busan under a weak offshore flow. As a result of wind vector, ZVB (Zero Velocity Boundary), potential temperature obtained the uMM5, at 0900 LST, SB advanced below 200 m height in the coastal areas and the internal boundary grew with the urban coastal region. At noon, the height of the SB head with updraft was approximately one and a half times (~600 m) higher than its depth in central urban. Applying the frontogenesis function, the SB structure for frontogenesis and frontolysis were complicated spatially; the dynamic effects of wind (i.e. convergence and tilting term) could play an important role in the growth of SB, especially the convergence effect.

• International Journal of High-Rise Buildings
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• v.8 no.4
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• pp.255-264
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• 2019

This paper describes large eddy simulation of wind pressures on a square cylinder in a uniform flow and a high-rise building immersed in an atmospheric turbulent boundary layer. For the atmospheric boundary layer case, the inflow turbulence is generated by a numerical wind tunnel. In the numerical simulation, particular attention is devoted to the performance of an auto hexahedral non-structural mesh. Both simulations are performed for three grid systems: an auto hexahedral non-structured grid, a structured Cartesian grid and a non-structured triangular prism grid, and for three grid numbers. The present study shows that the auto hexahedral unstructured mesh achieves the best simulation results for wind pressures on the square cylinder and the high-rise building. When the grid number is sufficiently large, the differences among the results obtained from the three investigated grid systems are not significant. However, the advantage of the auto hexahedral unstructured mesh becomes clear when the grid number decreases, because it enables a balanced distribution of orthogonal grids. The results described in this paper demonstrate that the auto hexahedral non-structured mesh has good potential applicability to simulation of urban flows.

• Journal of Environmental Science International
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• v.11 no.5
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• pp.419-436
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• 2002

The current paper reports on the enhancement of O$_3$, CO, NO$_2$, and aerosols during the Asian dust event that occurred over Korea on 1 May 1999. To confirm the origin and net flux of the O$_3$, CO, NO$_2$, and aerosols, the meteorological parameters of the weather conditions were investigated using Mesoscale Meteorological Model 5(MM5) and the TOMS total ozone and aerosol index, the back trajectory was identified using the Hybrid Single-Particle Lagrangian Integrated Trajectory Model(HYSPLIT), and the ozone and ozone precursor concentrations were determined using the Urban Ashed Model(UAM). In the presence of sufficiently large concentrations of NO$\sub$x/, the oxidation of CO led to O$_3$ formation with OH, HO$_2$, NO, and NO$_2$ acting as catalysts. The sudden enhancement of O$_3$, CO, NO$_2$ and aerosols was also found to be associated with a deepening cut-off low connected with a surface cyclone and surface anticyclone located to the south of Korea during the Asian dust event. The wave pattern of the upper trough/cut-off low and total ozone level remained stationary when they came into contact with a surface cyclone during the Asian dust event. A typical example of a stratosphere-troposphere exchange(STE) of ozone was demonstrated by tropopause folding due to the jet stream. As such, the secondary maxima of ozone above 80 ppbv that occurred at night in Busan, Korea on 1 May 2001 were considered to result from vertical mixing and advection from a free troposphere-boundary layer exchange in connection with an STE in the upper troposphere. Whereas the sudden enhancement of ozone above 100 ppbv during the day was explained by the catalytic reaction of ozone precursors and transport of ozone from a slow-moving anticyclone area that included a high level of ozone and its precursors coming from China to the south of Korea. The aerosols identified in the free troposphere over Busan, Korea on 1 May 1999 originated from the Taklamakan and Gobi deserts across the Yellow River. In particular, the 1000m profile indicated that the source of the air parcels was from an anticyclone located to the south of Korea. The net flux due to the first invasion of ozone between 0000 LST and 0600 LST on 1 May 1999 agreed with the observed ground-based background concentration of ozone. From 0600 LST to 1200 LST, the net flux of the second invasion of ozone was twice as much as the day before. In this case, a change in the horizontal wind direction may have been responsible for the ozone increase.

• International Journal of Aeronautical and Space Sciences
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• v.13 no.1
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• pp.43-57
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• 2012

In a modern aircraft, there are many variations in its mass, stiffness, and aerodynamic characteristics. Recently, an analytical approach was proposed, and this approach uses the idea of uncertainty to find out the most critical flight flutter boundary due to the variations in such aerodynamic characteristics. An analytical method that has been suggested to predict robust stability is the mu method. We previously analyzed the robust flutter boundary by using the mu method, and in that study, aerodynamic variations in the Mach number, atmospheric density, and flight speed were taken into consideration. The authors' previous attempt and the results are currently quoted as varying Mach number mu analysis. In the author's previous method, when the initial flight conditions were located far from the nominal flutter boundary, conservative predictions were obtained. However, relationships among those aerodynamic parameters were not applied. Thus, the varying Mach number mu analysis results required validation. Using an optimization approach, the varying Mach number mu analysis was found out to be capable of capturing a reasonable robust flutter boundary, i.e., with a low percentage difference from boundaries that were obtained by optimization. Regarding the optimization approach, a discrete nominal flutter boundary is to be obtained in advance, and based on that boundary, an interpolated function was established. Thus, the optimization approach required more computational effort for a larger number of uncertainty variables. And, this produced results similar to those from the mu method which had lower computational complexity. Thus, during the estimation of robust aeroelastic stability, the mu method was regarded as more efficient than the optimization method was. The mu method predicts reasonable results when an initial condition is located near the nominal flutter boundary, but it does not consider the relationships that are among the aerodynamic parameters, and its predictions are not very accurate when the initial condition is located far from the nominal flutter boundary. In order to provide predictions that are more accurate, the relationships among the uncertainties should also be included in the mu method.

• Journal of the Korean earth science society
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• v.32 no.4
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• pp.373-387
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• 2011

In this study, four types of sensitivity experiments (EG, EE, NG, NE; E: ERA-Interim, N: NCEP/DOE2, G: Grell scheme, E: Emanuel scheme) were performed to evaluate the simulation skills of RegCM4 released in July 2010 over the CORDEX (COordinated Regional Downscaling EXperiment) East Asia domain based on the combinations of boundary conditions (BC: ERA-Interim, NCEP/DOE2) and the cumulus parameterization schemes (CPS: Grell, Emanuel) for the 1989. The surface air temperature and precipitation data observed by the Korea Meteorological Adminstration were used to validate the simulation results over South Korea. The RegCM4 well simulates the seasonal and spatial variations of temperature but it fails to capture the seasonal and spatial variations of precipitation without consideration of the BC and CPS. Especially the simulated summer precipitation amount is significantly less in EG, NG, and NE experiments. But the seasonal variation of precipitation including summer precipitation is relatively well simulated in the EE experiment. The EE experiment shows a better skill in the seasonal march of East Asia summer monsoon, distribution of precipitation intensity and frequency than other experiments. In general, the skills of RegCM4 for temperature and precipitation are better during winter than summer, and in Emanuel than Grell schemes. The simulation results are more impacted by cumulus parameterization schemes than boundary conditions.

• Atmosphere
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• v.22 no.1
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• pp.97-107
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• 2012

To investigate variation of aerosol number concentration at each different size with three-dimensional (3D) wind components in ocean area, aerosol particles and 3D wind components were measured in the Ieodo Ocean Research Station, which is located to 419 km southwest from Marado, the southernmost island of Korea, from 25 June to 8 July 2010. The Laser Particle Counter (LPC) and ultrasonic anemometer were used to measure the size of aerosol particles and 3D wind components (zonal (u), meridional (v), and vertical (w) wind) respectively. Surface weather chart, NCEP/NCAR reanalysis data and sounding data were used to analyze the synoptic condition. The distribution of aerosol number concentration had a large variation from bigger particles more than 1.0 ${\mu}m$ in diameter by wind direction during precipitation. In the number concentration of aerosol particles with respect to the weather conditions, particles larger than 1.0 ${\mu}m$ in size were decreased and sustained to the similar concentration at smaller particles during precipitation. The increase in aerosol number concentration was due to the sea-salt particles which was suspended by southwesterly and upward winds. In addition, the aerosol number concentration with vertical wind flow could be related with the occurrence and increasing mechanism of aerosol in marine boundary layer.

• Proceedings of the Korean Environmental Sciences Society Conference
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• 2003.11a
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• pp.89-94
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• 2003

The formation of a severe snow storm occurred in the mountainous coastal region near Mt. Taegualyang and Kangnung city in the eastern part of Korea was investigate from 0900LST, December 7 through 9, 2002, using MM5 model. As synoptic scale easterly wind induced a great amount of moisture from the East Sea into the inland coastal region and sea-breeze further induced more moisture from the basin toward the top of the mountain side. The lifted moisture toward the mountain top was cooled down along the eastern slope of the mountain and near the mid of the mountain the moisture was much cooled down with relative humidity of 100％ under the air temperature below $O^{\circ}C$, resulting in the formation of snow. Relative humidity of 100％ generally occurred at the 5km away from the coast toward the inland mountain and the band of 100％ RH was parallel to the coastal line. The 100％ band coincided with minimum air temperature band and line.