• Korean Journal of Remote Sensing
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• v.37 no.5_3
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• pp.1447-1460
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• 2021

Urbanization increases the amount of impervious surface and artificial heat emission, resulting in urban heat island (UHI) effect. Local climate zones (LCZ) are a classification scheme for urban areas considering urban land cover characteristics and the geometry and structure of buildings, which can be used for analyzing urban heat island effect in detail. This study aimed to examine the UHI effect by urban structure in Suwon and Daegu using the LCZ scheme. First, the LCZ maps were generated using Landsat 8 images and convolutional neural network (CNN) deep learning over the two cities. Then, Surface UHI (SUHI), which indicates the land surface temperature (LST) difference between urban and rural areas, was analyzed by LCZ class. The results showed that the overall accuracies of the CNN models for LCZ classification were relatively high 87.9% and 81.7% for Suwon and Daegu, respectively. In general, Daegu had higher LST for all LCZ classes than Suwon. For both cities, LST tended to increase with increasing building density with relatively low building height. For both cities, the intensity of SUHI was very high in summer regardless of LCZ classes and was also relatively high except for a few classes in spring and fall. In winter the SUHI intensity was low, resulting in negative values for many LCZ classes. This implies that UHI is very strong in summer, and some urban areas often are colder than rural areas in winter. The research findings demonstrated the applicability of the LCZ data for SUHI analysis and can provide a basis for establishing timely strategies to respond urban on-going climate change over urban areas.

• Journal of Environmental Science International
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• v.23 no.9
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• pp.1619-1626
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• 2014

We analyzed diurnal variations in the surface air temperature using the high density urban climate observation network in Daegu metropolitan city, the representative basin-type city in Korea, in summer, 2013. We used a total of 28 air temperature observation points data(16 thermometers and 12 AWSs). From the distribution of monthly average air temperature, air temperature at the center of Daegu was higher than the suburbs. Also, the days of daily minimum air temperature more than or equal to $25^{\circ}C$ and daily maximum air temperature more than or equal to $35^{\circ}C$ at the schools near the center of Daegu was more than those at other schools. This tendency appeared more clearly on the days of daily minimum air temperature more than or equal to $25^{\circ}C$. Also, the air temperature near the center of the city was higher than that of the suburbs in the early morning. Thus it was indicated that the air temperature was hard to decrease as the bottom of the basin. From these results, the influence of urbanization to the formation of the daily minimum temperature in Daegu was indicated.

• Korean Journal of Remote Sensing
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• v.32 no.4
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• pp.353-364
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• 2016

Yangon city is experienced a rapid urban expansion over the last two decades due to accelerate with the socioeconomic development. This research work studied an investigation into the application of the integration of the Remote Sensing (RS) and Geographic Information System (GIS) for observing Land Use and Land Cover (LULC) patterns and evaluate its impact on Land Surface Temperature (LST) of the downtown, suburban 1 and suburban 2 of Yangon city. The main purpose of this paper was to examine and analyze the variation of the spatial distribution property of the LULC of urban spatial information related with the LST and Normalized Difference Vegetation Index (NDVI) using RS and GIS. This paper was observed on image processing of LULC classification, LST and NDVI were extracted from Landsat 8 Operational Land Imager (OLI) image data. Then, LULC pattern was linked with the variation of LST data of the Yangon area for the further connection of the correlation between surface temperature and urban structure. As a result, NDVI values were used to examine the relation between thermal behavior and condition of land cover categories. The spatial distribution of LST has been found mixed pattern and higher LST was located with the scatter pattern, which was related to certain LULC types within downtown, suburban 1 and 2. The result of this paper, LST and NDVI analysis exhibited a strong negative correlation without water bodies for all three portions of Yangon area. The strongest coefficient correlation was found downtown area (-0.8707) and followed suburban 1 (-0.7526) and suburban 2(-0.6923).

• Journal of the Korean Regional Science Association
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• v.33 no.2
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• pp.47-59
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• 2017

The purpose of this study is to examine various definitions of urban heat island and to analyze the characteristics and differences of each methodology by applying each methodology for deriving the heat island region to Seoul. The definition of the heat island is divided into the atmospheric heat island and the surface heat island according to the utilized temperature data. The methodology for deriving the heat island area differs depending on the comparison method and the spatial extent of the analysis. As a result of analyzing each methodology for Seoul city, it was confirmed that the heat island area of Seoul is different according to temperature data. Also, it is confirmed that the distribution range of the heat island area is different according to the spatial range of analysis. This shows that even if the heat island area is analyzed for the same space and the same view point, the heat island area is derived differently according to each methodology. This study can be used as a basic study to solve the urban heat island problem in the future.

• Journal of Korean Society for Atmospheric Environment
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• v.9 no.4
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• pp.303-309
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• 1993

An observational study of urban heat island was carried out using field data obatined during 6 days in May and August 1992 in Chunchon(population size 180.000). Air temperature was measured at 64 points along two sampling ruoutes by themisters attached to cars. Both routes cover urban and rural area and across the cneter of urban area. Continuous observation of air sonde was perfomed to clarify heights of nocturnal boundary layer(NBL) at the center of urban area. Surface meteorological observations were performed at both urban and rural sites. This study showed that heat island phenomena was obviously observed at the urbanized area during the night time with low wind speed. The average NBL heights exteded to about 10 meters, but varied with meteorological conditions. After sunset, the air temperature decreased with time at both sites and cooling rate at the urban site was greater than the rural site. The maximum heat island intensity was 7.5$^{\circ}$C at 21 LST, May 4. Usingthe two meteorological data sets obtained from urban and rural sites, the air pollutant concentration was calculated by Gaussian plume model which can obtain not only horizontal distribution of concentration but also vertical distribution. The result indicated that the concentration resulted from urban meteorological data set was lower than that from rural meteorological data set. It was also calculated that the air pollutant extended to higher level in urban meteorological data set than that in rural meteorological data set.

• Journal of the Korean Solar Energy Society
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• v.39 no.6
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• pp.67-82
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• 2019

This study aims to examine the impacts of built environmental features on the nocturnal and diurnal temperatures during the heat wave season in Gwangju, Korea. Built environmental measures are summarized at micro-scale level, such as 50 meters and 100 meters from temperature monitoring spots. Regressing the built environment on nocturnal and diurnal temperatures, we estimate how the artificial constructs contribute to temperature either day and night times. We found that impervious surface ratio is positively and negatively associated with nocturnal and diurnal temperatures, respectively. Buildings and structures tend to construct high thermal mass and absorb heat during day time and emit it for the night time. This property contributes to the nocturnal temperature model. On the other hand, urban areas with more vertical structure tend to block sun radiation more than rural, and it is more likely to find the negative relationship between impervious surface ratio and the diurnal temperatures.

• Journal of Climate Change Research
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• v.7 no.3
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• pp.357-371
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• 2016

Buildings in the city acts as a cause of distorted wind direction, wind speed, causing the stagnation of the air flow. In the recent trend of climate change can not but consider the temperature rise of the urbanization. This study was aimed to analyze the thermal comfort of planetary boundary layer in different artificial constructions areas which has a direct impact on urban climate, and estimating the warming phenomena. Envi-met model was used to consider the urban structure associated with urban growth in order to precisely determine the impact of the building on the city weather condition. The analyzed values of thermal comfort index were temperature, wind speed, horizontal and vertical turbulent diffusivity. In particular, analysis of the PPD(Predicted Percentage of Dissatisfied) represents the human thermal comfort. In this study, by adjusting the arrangement and proportion of the top floor building in the urban it was found that the inflow of the fresh air and cooling can be derived low PPD. Vertical heat flux amount of the city caused by climate change was a factor to form a high potential temperature in the city and the accumulation of cold air does not appear near the surface. Based on this, to make the city effectively respond to climate change may require a long-term restructuring of urban spatial structure and density management.

• Journal of the Korean Association of Geographic Information Studies
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• v.15 no.1
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• pp.133-143
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• 2012

The purpose of this study is to investigate the characteristics of urban heat island considering urban space at nighttime. We used to analyze landuse and landcover data of 1:1,000 scale, DTM, and surface temperature extracted ASTER image satellite of nighttime. According to the analytical results, heat intensity in single-family residential is higher than that in industrial area, public facility area, and commercial area because the anthropogenic heat by energy consumption is released. Likewise, the temperature difference were big in the buildings of industrial area depending on operating hours. Meanwhile, green and river area had cooling impacts mitigating the urban heat island. Therefore, we have to mitigate heat intensity through constructing green space and waterfront area. As mentioned above, we think that the results of this study will be used as base data for effective spatial planning when formulating development planning to mitigate urban heat island at nighttime.

• Journal of the Korean Society of Environmental Restoration Technology
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• v.24 no.6
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• pp.109-119
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• 2021

Thermal environment of city is getting worse due to severe urban heat island caused by climate change and urbanization. Green roof improves the urban thermal environment and save the cooling energy in buildings. This study presented a green roof combined with a storage system that stores rain-water and supplies water through a wick and evaluated the temperature reduction effect as surface temperature and amount of evapotranspiration. For about a week, the surface temperature using a infrared thermal imager and the evapotranspiration by recording change of module weight were measured at intervals of 30 minutes from sunrise to sunset. The results show that the mean surface temperature of the green roof was 15.4 degrees lower than that of the non-green roof from 12:00 P.M. to 14:00 P.M. There was no significant difference between mean surface temperature of green roof with and without storage system immediately after rain, but more than a week after rain, there was a difference with average of 2.49 degrees and maximum of 4.72 degrees. The difference in daily amount of evapotranspiration was measured to be 1.66 times on average. As drought stress increased over time, the difference in daily amount of evapotranspiration and surface temperature between with/without storage system increased simultaneously. The results of the study show a more excellent cooling effect of green roof combined with the rainwater storage system.

• Spatial Information Research
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• v.20 no.4
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• pp.1-16
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• 2012

There is no doubt that the urban heat island (UHI) is a mounting problem in built-up environments, due to energy retention by the surface materials of dense buildings, leading to increased temperatures, air pollution, and energy consumption. To investigate the UHI, three-dimensional (3-D) information is necessary to analyze complex sites, including dense building clusters. In this research, 3-D building geometry information is combined with two-dimensional (2-D) urban surface information to examine the relationship between urban characteristics and temperature. In addition, this research introduces spatial regression models to account for the spatial spillover effects of urban temperatures, and includes the following steps: (a) estimating urban temperatures, (b) developing a 3-D city model, (c) generating urban parameters, and (d) conducting statistical analyses using both Ordinary Least-Squares (OLS) and Spatial Regression Models. The results demonstrate that 3-D urban characteristics greatly affect temperatures and that neighborhood effects are critical in explaining temperature variations. Finally, the implications of the results are discussed, providing guidelines for policies to reduce the UHI.