Abstract
This study was to investigate the user's thermal environments under the pergola($L\;7,200{\times}W\;4,200{\times}H\;2,700mn$) covered with Wisteria floribunda(Willd.) DC. according to the variation of leaf area index(LAI). We carried out detailed measurements with two human-biometeorological stations on a popular square Jinju, Korea($N35^{\circ}10^{\prime}59.8^{{\prime}{\prime}}$, $E\;128^{\circ}05^{\prime}32.0^{{\prime}{\prime}}$, elevation: 38m). One of the stations stood under a pergola, while the other in the sun. The measurement spots were instrumented with microclimate monitoring stations to continuously measure air temperature and relative humidity, wind speed, shortwave and longwave radiation from the six cardinal directions at the height of 0.6m so as to calculate the Universal Thermal Climate Index(UTCI) from $9^{th}$ April to $27^{th}$ September 2017. The LAI was measured using the LAI-2200C Plant Canopy Analyzer. The analysis results of 18 day's 1 minute term human-biometeorological data absorbed by a man in sitting position from 10am to 4pm showed the following. During the whole observation period, daily average air temperatures under the pergola were respectively $0.7{\sim}2.3^{\circ}C$ lower compared with those in the sun, daily average wind speed and relative humidity under the pergola were respectively 0.17~0.38m/s and 0.4~3.1% higher compared with those in the sun. There was significant relationship in LAI, Julian day number and were expressed in the equation $y=-0.0004x^2+0.1719x-11.765(R^2=0.9897)$. The average $T_{mrt}$ under the pergola were $11.9{\sim}25.4^{\circ}C$ lower and maximum ${\Delta}T_{mrt}$ under the pergola were $24.1{\sim}30.2^{\circ}C$ when compared with those in the sun. There was significant relationship in LAI, reduction ratio(%) of daily average $T_{mrt}$ compared with those in the sun and was expressed in the equation $y=0.0678{\ln}(x)+0.3036(R^2=0.9454)$. The average UTCI under the pergola were $4.1{\sim}8.3^{\circ}C$ lower and maximum ${\Delta}UTCI$ under the pergola were $7.8{\sim}10.2^{\circ}C$ when compared with those in the sun. There was significant relationship in LAI, reduction ratio(%) of daily average UTCI compared with those in the sun and were expressed in the equation $y=0.0322{\ln}(x)+0.1538(R^2=0.8946)$. The shading by the pergola covered with vines was very effective for reducing daytime UTCI absorbed by a man in sitting position at summer largely through a reduction in mean radiant temperature from sun protection, lowering thermal stress from very strong(UTCI >$38^{\circ}C$) and strong(UTCI >$32^{\circ}C$) down to strong(UTCI >$32^{\circ}C$) and moderate(UTCI >$26^{\circ}C$). Therefore the pergola covered with vines used for shading outdoor spaces is essential to mitigate heat stress and can create better human thermal comfort especially in cities during summer. But the thermal environments under the pergola covered with vines during the heat wave supposed to user "very strong heat stress(UTCI>$38^{\circ}C$)". Therefore users must restrain themselves from outdoor activities during the heat waves.
본 연구는 등(Wisteria floribunda(Willd.) DC.)으로 피복된 그늘시렁($L\;7,200{\times}W\;4,200{\times}H\;2,700mn$)의 엽면적지수(LAI)의 변동에 따른 온열환경을 규명하고자 한 것이다. 이를 위해 진주시내 광장($N35^{\circ}10^{\prime}59.8^{{\prime}{\prime}}$, $E128^{\circ}05^{\prime}32.0^{{\prime}{\prime}}$, 표고: 38m)의 등으로 피복된 그늘시렁 하부와 햇빛에 노출된 포장지를 대상으로 맑은 날 미기상을 측정하였다. 범용온열기후지수(UTCI)를 산정하기 위해 봄철과 여름철의 미기상환경으로서 지상 60cm 높이에서 기온, 풍속, 상대습도 그리고 6방향의 장파 및 단파복사를 2017년 4월 9일부터 8월 27일까지 측정하였다. 또한, LAI는 LAI-2200C 수관분석기로 측정하였다. 18일간 오전 10시부터 오후 4시까지의 앉은 자세의 인체가 흡수한 매 1분 간격 인체-생기상학적 자료를 분석한 결과는 다음과 같다. 측정기간 동안 햇빛노출지에 비해 그늘시렁 하부의 일평균 기온은 $0.7{\sim}2.3^{\circ}C$ 낮았으며, 일평균 풍속과 일평균 상대습도는 각각 0.17~0.38m/s와 0.4~3.1% 높았다. LAI와 쥴리안 데이 사이의 회귀식은 $y=-0.0004x^2+0.1719x-11.765(R^2=0.9897)$였다. 그늘시렁 하부의 일평균 평균복사온도($T_{mrt}$) 값은 햇빛 노출지에 비해 각각 $11.9{\sim}25.5^{\circ}C$로 낮았으며, 최대 평균복사온도 감소(${\Delta}T_{mrt}$)는 $24.1{\sim}30.2^{\circ}C$였다. LAI의 변동에 따른 햇빛 노출지 대비 일평균 $T_{mrt}$ 감소율(%) 사이의 회귀식은 $y=0.0678{\ln}(x)+0.3036(R^2=0.9454)$였다. 그늘시렁 하부의 일평균 UTCI 값은 햇빛 노출지에 비해 각각 $4.1{\sim}8.3^{\circ}C$로 낮았으며, 최대 범용온열기후지수 감소 값(${\Delta}UTCI$)는 $7.8{\sim}10.2^{\circ}C$였다. LAI의 변동에 따른 햇빛 노출지 대비 일평균 UTCI 감소율(%) 사이의 회귀식은 $y=0.0322{\ln}(x)+0.1538(R^2=0.8946)$였다. 종합적으로 보면 여름철에 덩굴식물로 피복된 그늘시렁에 의한 녹음은 차양에 의한 $T_{mrt}$의 감소를 통해 낮 동안 UTCI를 감소시킴으로써 열스트레스를 매우 강한(UTCI>$38^{\circ}C$) 또는 강한(UTCI >$32^{\circ}C$) 단계에서 강한(UTCI >$32^{\circ}C$) 또는 보통(UTCI >$26^{\circ}C$) 단계로 낮추어 준다. 따라서 여름철 열스트레스를 완화하고 쾌적한 인체 온열쾌적성을 제공하기 위해서는 덩굴식물로 피복된 그늘시렁의 도입은 필수적이다. 하지만 폭염 시에는 덩굴식물로 피복된 그늘시렁 하부의 온열환경도 이용자들에게 매우 강한 열 스트레스(UTCI >$38^{\circ}C$)를 주므로 노약자의 옥외활동은 자제시킬 필요가 있다고 판단된다.