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The Comparison of the Solar Radiation and the Mean Radiant Temperature (MRT) under the Shade of Landscaping Trees in Summertime

하절기 조경용 녹음수 수관 하부의 일사와 평균복사온도 비교

  • Lee, Chun-Seok (Dept. of Landscape Architecture, Gyeongnam National University of Science and Technology) ;
  • Ryu, Nam-Hyung (Dept. of Landscape Architecture, Gyeongnam National University of Science and Technology)
  • 이춘석 (경남과학기술대학교 조경학과) ;
  • 류남형 (경남과학기술대학교 조경학과)
  • Received : 2014.07.16
  • Accepted : 2014.09.04
  • Published : 2014.10.31

Abstract

The purpose of this study was to compare the Solar Radiation(SR) and the Mean Radiant Temperature(MRT) under the shades of the three landscaping trees in clear summer daytimes. The trees were Lagerstroemia indica, Quercus palustris and Ulmus parvifolia. The solar radiation, the globe temperature and the air temperature were recorded every minute from the $1^{st}$ of April to the $30^{th}$ of September 2013 at a height of 1.1m above on the four monitoring stations, with four same measuring system consisting of a solar radiation sensor, two resistance temperature detectors(Pt-100), a black brass globe (${\phi}50mm$) and data acquisition systems. At the same time, the sky view photos were taken automatically hourly by three scouting cameras(lens angle: $60^{\circ}$) fixed at each monitoring station. Based on the 258 daily sky view photos and 6,640 records of middays(10 A.M.~2 P.M.) from the $1^{st}$ of June to the $30^{th}$ of August, the time serial differences of SR and MRT under the trees were analysed and compared with those of open sky, The major findings were as follows; 1. The average ratio of sky views screened by the canopies of Quercus palustris, Lagerstroemia indica and Ulmus parvifolia were 99%, 98% and 97%, and the SR were $106W/m^2$, $163W/m^2$ and $202W/m^2$ respectively, while the SR of open sky was $823W/m^2$. Which shows the canopies blocked at least 70% of natural SR. 2. The average MRT under the canopies of Quercus palustris, Lagerstroemia indica and Ulmus parvifolia were $30.34^{\circ}C$, $33.34^{\circ}C$ and $34.77^{\circ}C$ respectively, while that of open sky was $46.0^{\circ}C$. Therefore, it can be said that the tree canopies can reduce the MRT around $10{\sim}16^{\circ}C$. 3. The regression test showed significant linear relationship between the SR and MRT. In summary, the performances of the landscaping shade trees were very good at screening the SR and reducing the MRT at the outdoor of summer middays. Therefore, it can be apparently said that the more shade trees or forest at the outdoor, the more effective in conditioning the outdoor space reducing the MRT and the useless SR for human activities in summertime.

조경용 녹음수가 하절기 옥외공간에서 인간이 느끼는 열쾌적성에 미치는 효과를 객관적으로 검증하기 위하여 수형이 서로 다른 미국참나무, 배롱나무, 참느릅나무 등 세 종의 수목를 선정하여 일사차단율과 평균복사온도 저감 효과를 비교분석하였다. 또한, 주기적으로 수관부 사진을 촬영하여 수관부의 변화특성도 비교 검토하였다. 일사량과 건구온도, 흑구온도를 현장에서 자동으로 계측 기록할 수 있는 시스템을 구축하여 각 수목의 수관 하부에 지면으로부터 1.1m 위치에 설치하고, 2013년 4월 1일부터 동년 11월 30일까지 매 분 단위로 기록될 수 있도록 설정하였다. 수관의 천공차폐율 분석결과, 비교적 일정한 상태를 유지한 것으로 나타난 2013년 6월 1일부터 동년 8월 30일까지의 자료 중, 우천과 이상 기상일 자료를 제외한 오전 10시에서 오후 2시까지의 자료를 통계 분석에 이용하였다. 10분 단위 평균값으로 환산된 총 6,640건의 흑구온도와 건구온도를 바탕으로 평균복사온도를 환산하였으며, 이를 각 시험구의 일사량과 비교 분석하였다. 분석 대상 기간 중 미국참나무와 배롱나무, 참느릅나무 수관부의 평균 천공차폐율은 각각 99%, 98%, 97%였으며, 각 수관하부에 도달한 평균 태양 복사량은 $106W/m^2$, $163W/m^2$, $202W/m^2$로 대조구의 $823W/m^2$와 비교했을 때, 최소 75%이상이 차단된 것으로 나타났다. 또한, 평균복사온도의 경우, 각각 $30.34^{\circ}C$, $33.34^{\circ}C$, $34.77^{\circ}C$로 계산되어 대조구의 $46.0^{\circ}C$와 비교했을 때, 적게는 $10^{\circ}C$에서 많게는 $16^{\circ}C$까지 수목의 수관부에 의해서 저감된 것으로 나타났다. 일사량과 평균복사온도의 관계를 회귀분석한 결과, 매우 밀접한 선형관계를 형성하고 있었으며, 설명력도 매우 높게 분석되었다. 결론적으로 본 연구를 통해서 하절기 옥외공간에서 녹음수의 수관은 일사량의 상당부분을 차단함으로써 인간이 체감하는 열쾌적성을 개선하는데 매우 중요한 역할을 하고 있다는 점을 객관적으로 확인할 수 있었다. 따라서, 옥외공간에 더 많은 녹음수와 숲을 조성하여 그늘 지역을 증가시킴으로써 인간의 하절기 옥외활동에 부정적 영향을 주고 있는 불필요한 열에너지를 현격하게 저감시켜 쾌적한 열환경을 효과적으로 조성할 수 있을 것이다.

Keywords

References

  1. Ahn, Tong-Mahn, Jae-Won Lee, Bo-Ram Kim, Ho-Seon Yoon, Seung-Woo Son, Yoo Choi, Na-Rae Lee, Ji-Young Lee and Hae-Ryung Kim (2013) An analysis of thermal comforts for pedestrians by WBGT measurement on the urban street greens. Journal of the Korean Institute of Landscape Architecture 41(3): 22-30. https://doi.org/10.9715/KILA.2013.41.3.022
  2. Choi, Dong-Ho and Bu-Yong Lee(2006) Analysis of passive cooling effect of the tree by field observations in the summer. Journal of the Korean Solar Energy Society 26(4): 109-118.
  3. Choi, Dong-Ho and Bu-Yong Lee(2007) Analysis of passive cooling effect of membrane shading structure and the tree by field observations in the summer. Journal of the Korean Solar Energy Society 27(4): 137-146.
  4. Epstein, Y. and D. S. Moran(2006) Thermal comfort and the heat stress indices. Industrial Health 44: 388-398. https://doi.org/10.2486/indhealth.44.388
  5. ISO 7726(2001) Ergonomics of the Thermal Environment - Instruments for Measuring Physical Quantities.
  6. ISO 7730(2005) Ergonomics of the Thermal Environment - Analytical Determination and Interpretation of the Thermal Comfort Using Calculation of the PMV and PPD Indices and Local Thermal Comfort Criteria.
  7. Ju, Min-Jin, Chun-Seok Lee and Nam-Hyung Ryu(2004) The effect of urban shade trees on the WBGT(wet bulb glove thermometer index). Journal of the Korean Institute of Landscape Architecture 32(3): 51-59.
  8. Lee, Chun-Seok and Nam-Hyung Ryu(2010) The influence of landscaping pavements on the WBGT of outdoor spaces without ventilation or shade at summer midday. Journal of the Korean Institute of Landscape Architecture 38(2): 1-8.
  9. Lee, Chun-Seok and Nam-Hyung Ryu(2012) The influence of ventilation and shade on the mean radiant temperature of summer outdoor. Journal of the Korean Institute of Landscape Architecture 40(5): 100-108. https://doi.org/10.9715/KILA.2012.40.5.100
  10. Park, Soo-kuk(2012) Landscape planning and design methods with human thermal sensation. Journal of the Korean Institute of Landscape Architecture 40(1): 1-11. https://doi.org/10.9715/KILA.2012.40.1.001
  11. Park, Soo-kuk(2013) A way for creating human bioclimatic maps using human thermal sensation(comfort) and applying the maps to urban and landscape planning and design. Journal of the Korean Institute of Landscape Architecture 40(1): 21-33. https://doi.org/10.9715/KILA.2013.41.1.021
  12. Potchter, Oded, Yaron Yaakov, Limor Shashua-Bar, Shabtai Cohen, Josef Tanny and Pua Bar-Kutiel(2011) The use of urban vegetation as a tool for heat stress mitigation in hot and arid regions, case study: Beer Sheva Israel. City Weather: Meteorology and Urban Design 1950-2010: 1-13.
  13. Ryu, Nam-Hyung and Chun-Seok Lee(2013) Pergola's shading effects on the thermal comfort index in the summer middays. Journal of the Korean Institute of Landscape Architecture 41(6): 52-61. https://doi.org/10.9715/KILA.2013.41.6.052
  14. Toy, S. and S. Yilmaz(2010) Evaluation of urban-rural bioclimatic comfort differences over a ten-year period in the sample of Erzincan city reconstructed after a heavy earthquake. Atmosfera 23(4): 387-402.
  15. http://www.comfile.co.kr