• Atmosphere
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• v.25 no.2
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• pp.193-203
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• 2015

A large aperture scintillometer (LAS) was deployed with an optical path length of 2.1 km to estimate turbulent sensible heat flux (${\mathcal{Q}}_H$) over a highly heterogeneous urban area. Scintillation measurements were conducted during cold season in November and December 2013, and the daytime data of 14 days were used in the analysis after quality control processes. The LAS-derived ${\mathcal{Q}}_H$ show reasonable temporal variation ranging $20{\sim}160W\;m^{-2}$ in unstable atmospheric conditions, and well compare with the measured net radiation. The LAS footprint analysis suggests that ${\mathcal{Q}}_H$ can be relatively high when the newly built-up urban area has high source contribution of the turbulent flux in the study area ('northwesterly winds'). Sensitivity tests show that the LAS-derived ${\mathcal{Q}}_H$ are highly sensitive to non-dimensional similarity function for temperature structure function parameter, but relatively less sensitive to surface aerodynamic parameters and meteorological variables (temperature and wind speed). A lower Bowen ratio also has a significant influence on the flux estimation. Overall uncertainty of the estimated daytime ${\mathcal{Q}}_H$ is expected within about 20% at an upper limit for the analysis data. It is also found that stable atmospheric conditions can be poorly determined when the scintillometry technique is applied over the highly heterogeneous urban area.

• Asian Journal of Atmospheric Environment
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• v.4 no.1
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• pp.42-54
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• 2010

Automobile emissions have caused a major hydrocarbon pollution problem in the ambient air of many cities around the world. This study was conducted to measure the pollution status of volatile organic compounds (VOCs) in some urban residential areas in Seoul, Korea. A total of 20 VOCs (11 aromatic and 9 chlorinated species) were identified at 4 urban residential sites in Seoul, Korea from February 2009 to July 2009. Comparison of total VOC (TVOC) concentration data indicated the dominance of the aromatic species with the maximum (72.2 ppbC) at Jong Ro (JR) and the minimum at Yang Jae (33.4 ppbC). The peak concentration of TVOC occurred during spring at all sites with an exception at Gang Seo (GS), where it was recorded during winter. The distribution of individual VOCs at the study sites was characterized by high toluene concentration. A strong correlation of benzene was also observed with other VOCs and criteria pollutants at all sites (except YJ). The overall results of this study suggest that vehicular emissions have greatly contributed to the increase in VOC pollution at all the study sites.

• Atmosphere
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• v.25 no.3
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• pp.449-459
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• 2015

Effects of buildings and topography on observation environment of surface wind in central regions of urban areas are investigated using a computational fluid dynamics (CFD) model. In order to reflect the characteristics of buildings and topography in urban areas, geographic information system (GIS) data are used to construct surface boundary input data. For each observation station, 16 cases with different inflow directions are considered to evaluate effects of buildings and topography on wind speed and direction around the observation station. The results show that flow patterns are very complicated due to the buildings and topography. The simulated wind speed and direction at the location of each observation station are compared with those of inflow. As a whole, wind speed at observation stations decreases due to the drag effect of buildings. The decrease rate of wind speed is strongly related with total volume of buildings which are located in the upwind direction. It is concluded that the CFD model is a very useful tool to evaluate location of observation station suitability. And it is expected to help produce wind observation data that represent local scale excluding the effects of buildings and topography in urban areas.

• Atmosphere
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• v.24 no.1
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• pp.69-76
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• 2014

Urbanization affects the local thermal environment due to the large scale land use changes. To investigate the weather environment change of large scale urban redevelopment, 9 surface temperature and humidity observations were accomplished at Eunpyeong new town area. The observation period is from March 2007 to February 2010. In the center of development area, the air temperature has increased and relative humidity has decreased, by the changes of the land cover and building construction. In the area where the green zone is maintained, air temperature and relative humidity were not changed significantly. The air temperature and relative humidity for the other development observation stations is decreased and increased, respectively. The relative temperature difference between study area and a neighboring rural location was increased during observation periods. The difference is the highest during winter. The urban-rural minimum temperature difference was increased at development area, which means that urbanization affects increasing of minimum temperature in study area.

• Journal of Korean Society for Atmospheric Environment
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• v.24 no.5
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• pp.551-561
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• 2008

In order to clarify the impact of anti-heat insulation pavement on the thermal structure of atmospheric boundary layer, field experiments and numerical simulations were carried out. Field experiment with various pavements were also conducted for 24 hours from 09LST 19 June 2007. And numerical experiment mainly focused on the impact of albedo variation, which is strongly associated with thermal characteristics of insulated pavement materials, on the temporal variation of planterly boundary layer. Numerical model used in this study is one dimension model with Planterly Boundary Layer developed by Oregon State University (OSUPBL). Because anti-heat insulation pavement material shows higher albedo value, not only maximum surface temperature but also maximum surface air temperature on anti-heat insulation pavement is lower than that on asphalt. The maximum value of surface temperature only reach on $49.5^{\circ}C$. As results of numerical simulations, surface sensible heat flux and the height of mixing layer are also influenced by the values of albedo. Therefore the characteristics of urban surface material and its impact on atmosphere should be clarified before the urban planning including improvement of urban heat environment and air quality.

• Proceedings of the Korea Water Resources Association Conference
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• 2007.05a
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• pp.1943-1947
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• 2007

The objective of this research was to find a direct and indirect method to estimate land surface temperature (LST) efficiently, using Landsat images and in-situ measurement. Agricultural fields including paddy fields have long been known to have multi-functions beneficial to the environment and ecology of the urban surrounding areas. Among these functions, the ambient temperature cooling (ATC) effect are widely acknowledged. However, quantitative and regional assessment of such effect has not had many investigations. Thermal remote sensing has been used over urban areas to assess ATC effect, to perform land cover classifications and as input for models of urban surface atmosphere exchange. Here, we review the use of thermal remote sensing in the study of paddy fields and urban climates, focusing primarily on the ATC effect. Landsat satellite images were used to determine the surface temperatures of different land cover types of a $441km^2$ study area in Cheongju, Korea. The results show that the ATC are a function of paddy area percentage in Landsat pixels. Pixels with higher paddy area percentage have more significant cooling effect.

• Journal of The Korean Society of Agricultural Engineers
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• v.48 no.5
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• pp.39-48
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• 2006

The objective of this research was to find an indirect method to estimate land surface temperature (LST) efficiently, using Landsat images. Agricultural fields including paddy fields have long been known to have multi-functions beneficial to the environment and ecology of the urban surrounding areas. Among these functions, the ambient temperature cooling (ATC) effect is widely acknowledged. However, quantitative and regional assessment of such effect has not been performed. Thermal remote sensing has been used over urban areas to assess the ATC effect, Thermal Island Effect(TIE), and as input for models of urban surface atmosphere exchange. Here, we review the use of thermal remote sensing in the study of paddy fields and urban climates, focusing primarily on the ATC effect. Landsat satellite images were used to determine the surface temperatures of different land cover types of a $44km^{2}$ study area in Cheongiu, Korea. The results show that the ATC is a function of paddy area percentage in Landsat pixels. Landsat pixels with higher paddy area percentage have much more cooling effect. The use of satellite data may contribute to a globally consistent method for analysis of ATC effect.

• Atmosphere
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• v.22 no.4
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• pp.429-436
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• 2012

The performances of the Seoul National University Urban Canopy Model (SNUUCM) under different meteorological conditions (clear, cloudy, and rainy conditions) in summertime are compared using observation dataset obtained at an urban site. The daily-averaged net radiation, sensible heat flux, and storage heat flux are largest in clear days and smallest in rainy days, but the daily-averaged latent heat flux is similar among clear, cloudy, and rainy days. That is, the ratio of latent heat flux to net radiation increases in order of clear, cloudy, and rainy conditions. In general, the performance of the SNUUCM is better in clear days than in cloudy or rainy days. However, the performance in simulating sensible heat flux in clear days is as poor as that in rainy days. For all the meteorological conditions, the performance in simulating latent heat flux is worst among the performances in simulating net radiation, sensible heat flux, and latent heat flux. The normalized mean error for latent heat flux is largest in rainy days in which the relative importance of latent heat flux in the surface energy balance becomes greatest among the three conditions. This study suggests that improvements to the parameterization of processes that are related to latent heat flux are particularly needed.

• Journal of Korean Society for Atmospheric Environment
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• v.12 no.2
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• pp.189-198
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• 1996

Mercury (Hg) is ubiquitous throughout the earth's atmosphere. The uniqueness of its atmospheric geochemistry is well-known with the high environmental mobility and relatively long atmospheric residence time (c.a., 1 year) associated with its high chemical stability. Despite a growing recognition of the environmental significance of its global cycling, the prexisting Korean database for atmospheric Hg is extremely rare and confined to a number of concentration measurements conducted under relatively polluted urban atmospheric environments. To help activate the research on this suvject, an in-depth analysis on the current development in the measurements of atmospheric mercury and the associated fluxes has been made using the most using the most updated data ests reported worldwide. As a first step toward this purpose, the most reliable techniques commonly employed in the measurements of its concentration in the background atmosphere are introduced in combination with the flux measurement techniques over soil surface such as: dynamic enclosure (or field flux chamber) method and field micrometeorological method. Then the results derived using these measurement techniques are discussed and interpreted with an emphasis on its mobilization across the terrestrial biosphere and atmosphere interface. A unmber of factors including air/soil temperature, soil chemical composition, soil water content, and barometric pressure are found out to be influential to the rate and amount of such exchange processes. Although absolute magnitude of such exchange processes is insignificant relative to that of the major component like the oceanic environment, this exchange process is thought to be the the predominant natural pathway for both the mobilization and redistribution of atmospheric Hg on a local or regional scale.

• Proceedings of the KSRS Conference
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• v.1
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• pp.305-307
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• 2006

A multi-spectral photometer was set up as an NASA/AERONET site at Kinki University campus in Higashi-Osaka in 2002 for measuring urban aerosols. In addition, the SPM-613D (Kimoto Electric) commenced measurement of suspended particles matter (SPM) as $PM_{10}$ and $PM_{2.5}$ on March 15, 2004 at the same AERONET site. The obtained results revealed that the poor air quality of the Higashi-Osaka site is due not only to anthropogenic particles from local emissions, such as diesel vehicles and chemical industries, but also to dust particles brought from continental desert areas by large scale climatic conditions. To understand the characteristics of background atmosphere over Higashi-Osaka, we examined the relationship between $PM_{2.5}$ concentration and aerosol optical thickness (AOT) at a wavelength of 0.87 μm based on AERONET data for background atmosphere (AOT<0.2). We obtained a linear regression line between AOT and $PM_{2.5}$ concentration. Using the linear relationships between AOT and $PM_{2.5}$, we show ground-level concentrations of $PM_{2.5}$ of background atmosphere from Terra/MODIS satellite measurements.