广州市城区公园对周边环境的降温效应

The cooling effect of Guangzhou City parks to surrounding environments

城市化的快速发展使得大量的人造建筑物取代了自然地表,极大的改变了城市的热环境,加速了城市的"热岛效应",给人类的身体健康、生活环境带来许多危害。以公园为主体的城市绿地通过植被的光合作用、蒸腾以及蒸散作用降低温度、增加湿度,是缓解城市热岛效应的有效途径之一。选取广州市城区17个公园作为研究对象,使用TM遥感影像反演公园周边温度,分析了公园周边温度的分布情况。研究表明,在一定范围内,公园周边温度与公园边界点温度的温差随着其远离公园边界距离的增大而增加,且增长趋势逐渐减缓,近似于一条过原点的三次多项式;公园的平均降温范围与公园绿地面积存在显著的正相关关系,拟合曲线近似于一种对数形式增加;水体面积比例较大的公园,比同等条件下水体面积较小的公园降温效果好;而长宽比较大(≥2)的公园,即使公园面积较小,降温效果也较明显。首次对广州市城区公园周边温度分布规律进行了定量研究,研究结果对像广州这样的大城市生态规划尤其是公园规划设计具有实质性的指导意义,也可为世界其他类似地区、城市进行公园规划设计提供重要的理论依据和参考价值。

Thermal infrared （TIR） remote sensing techniques have been used over urban areas and applied in urban climate and heat environmental studies for more than 30 years,mainly for analyzing land surface temperature （LST） distribution,difference and their relationship with city development and surface energy fluxes.The rapidly expanding urban areas of the world form an environmental challenge for the 21st century that requires both new analytic approaches and new sources of data and information.In developing countries,however,remote sensing may provide large-scale,fast and repeated observations of urban growth and environmental conditions that are usually not available from other sources or with high cost.Because of the rapid urbanization,large numbers of the natural surfaces in the city have been replaced by artificial surfaces.This has resulted in undesirable thermal impacts on city meteorological and ecological environment-Urban Heat Island （UHI）,especially bringing lots of negative effect to the health of human beings and living environments.Some studies have showed that the green land and water areas （mainly in city parks）,can just diminish UHI effect on temperature and increase air moisture through the photosynthesis,transpiration and evapotranspiration of vegetation around urban parks.In this paper,17 Guangzhou City parks were selected as the case areas and the temperature information was inversed from Landsat TM remote sensing data.After analyzing the temperature distribution patterns surrounding the 17 parks using field investigation,buffer area analysis and cubic polynomial fitting method,we find that the temperature differences between the surrounding sites and boundaries of park rise with the distances further away from the park boundaries.However,the temperature accretion rate is step-down at the same time.The shape of the temperature increasing curve is similar to a cubic polynomial through the origin of coordinates （R2 0.84）.The maximum cooling range model of city parks in Guangzhou was built.The maximum cooling ranges are from 14—432m;and the maximum cooling values of temperature are at about 1.9—4.3K.What is more,the average temperature decreasing range around parks has a positive relationship with the green area of parks,and the fitted curve is similar to that of a logarithmic.For those parks that the water-covered-rates are larger than 50%,their temperature cooling effects are always more remarkable.For those parks that the length-width-rates are more than or equal to 2,the temperature cooling effects are also more obvious,even if their park areas are smaller than others.From the viewpoint of the cooling effect of parks to their surrounding environment in Guangzhou,the optimal values of planned green land should be between about 4200 m2 and 540000 m2.Therefore,the park area and distance from boundary of a park played the significant role in changing the effect of UHI.This study is the first quantitative research on the temperature distributions of main parks＇ surroundings in Guangzhou City,which may be of the directive significance to the ecology planning （especially city parks） of large cities like Guangzhou City.It also provides a reference and theory basis for other cities to design and plan the city parks in the world.