Precedent Research
[김유진, 최영은(2012),「기상 조건에 따른 서울의 열섬 강도 특성에 관한 연구」, 『국토지리학회지』, 제 46권 1호]
Cities are densely populated in narrow areas, resulting in a city-specific climate that is different from the surrounding suburbs. In this study, the heat island intensity in Seoul was calculated using the time-based temperature data for the last 10 years (2001-2010) in Seoul and its surrounding areas(Yangpyeong, Icheon, Dongducheon) and the characteristics of heat island intensity according to weather conditions such as cloudiness, wind speed, and precipitation.
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In the study, the univariate characteristics of the annual and seasonal heat island intensity were identified, and the heat island intensity by time was calculated to set the highest heat island intensity of the day to the maximum heat island intensity.
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Change of heat island intensity
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Heat island intensity characteristics according to weather conditions
1. wind speed
When the wind speed is weak, the maximum heat island intensity has increased in all seasons, especially in winter.
Daily average wind speed correlation formula with maximum heat island intensity
per day and four points average
y = -0.983x + 5.089
2. cloudiness
On a clear day with the least cloudiness, the heat island intensity was the strongest, and the heat island strength weakened as the cloudiness increased. On clear days in all seasons, the maximum heat island intensity was great, especially the effect of cloudiness on the summer heat island intensity.
Daily mean cloudiness and maximum heat island intensity correlation formula
y = -0.180x + 4.452
3. precipitation
Heat island intensity appears strongest on days when no precipitation occurs. The maximum heat island intensity of no precipitation day increased in all seasons, especially in summer. When the precipitation occurs, the solar radiation energy entering is insufficient, and the heat energy absorbed by the urban surface decreases. In the surrounding area, the increased soil moisture absorbs heat. Accordingly, since the temperature difference between the city and the surrounding area decreases, the heat island intensity is lower on the precipitation day than on the no precipitation day.
Correlation between daily maximum heat island intensity and precipitation
: y = -0.026x + 3.645
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Conclusion
The heat island intensity was most affected by cloudiness in spring, summer and autumn, and the wind effect was most pronounced in winter, showing seasonal differences.
Table 1. Reference values for strength classification of weather conditions used in analysis
Figure 3. A change in Seoul's seasonal heat island intensity(2001-2010)
Figure 4. Average maximum heat island intensity and frequency of occurrence in Seoul(2001-2010)
[김용진, 강동화, 안건혁 (2011), 「기후변화에 따른 도시열섬현상 특성 변화와 도시설 계적 대안 모색에 관한 기초연구」, 『한국도시설계학회지 도시설계』, 제 12권 3호, pp. 5-14]
Urban heat island phenomenon in Korea, unlike many overseas cities that occur on a clear day, showed a characteristic that occurred even on cloudy days when solar radiation is blocked significantly due to the influence of the warm-humid North Pacific air mass.
In recent years, due to climate change, the rainy season is gradually shortening, and heavy rains are occurring more frequently. This has increased the number of hot, humid and low insolation days, deepening the situation. As a result of analysis, the urban heat island phenomenon on a clear day was found to be the main factors of altitude, wind speed, and green area. However, the urban heat island phenomenon on a cloudy day shows that the aspect ratio of the building is the main factor, and the urban heat island phenomenon is intensified by radiant heat.
When the urban heat island is strengthened by water vapor or other factors in the atmosphere, the strong local pressure that occurs rapidly in the city cannot flow through the advection and stays in the city, thereby developing precipitation in the form of a heavy rain.