Thermal Environment Response Of Urban Water Landscape

The rapid expansion of modern cities has had a profound impact on the internal environment of the city,which includes significantly exacerbated urban thermal environmental pressures.The natural landscape preserved in the city is an important ingredient in relieving the thermal environment.As a typical natural landscape,waters have the specific heat capacity and considerable shoreline ancillary landscape,resulting in a significant cooling effect.This study takes an example of area in Beijing sixth ring road,extracting the surface temperature and water information in the study area from the remote sensing image.The thermal environment effect of water landscape,which including time distribution characteristics,spatial distribution characteristics and characteristics of the waters themselves,is analyzed with land use cover data.The summer time,when the water has the most obvious cooling effect,was selected for further analysis.The water was re-extract from high-resolution images and was divided into two parts: planar and linear to further research,field measurement data was also considered.The result indicating:(1)NDWI index was negatively correlated with water temperature,which means better quality water has a more pronounced cold island effect.In different seasons,the water's cooling distance is basically the same,ranging from 120 m to 150 m.While the cooling rate is greater in the summer,and is closely related to the surrounding landscape.In winter,the cooling rate is smaller and less relevant to the surrounding landscape.In terms of spatial distribution,high temperature water bodies are distributed within the fifth ring road;medium temperature water bodies are widely distributed,but inside fifth ring road are concentrated in the northeast side and south side;low temperature water bodies are distributed in the center to the northeast region inside fifth ring road and the edge of the sixth ring road.(2)For planar water,the average cooling distance is between 120 m ~ 150 m.There is a significantly difference between water and land temperature.The water area is negatively correlated with the water temperature and positively correlated with the temperature difference between water and land,while the perimeter area ratio is opposite.And the correlation between the shape index and the water temperature is small.For the composition of the surrounding landscape,the proportion of hardened surface is positively correlated with the mean temperature of water,while The correlation of the remaining parameters is small,which means the influence of the water body itself is more obvious than that of the surrounding landscape to the planar water.(3)For linear water,their cold land effect is not obvious.But their energetic exchanging with the surrounding landscape is frequently,which resulting in smaller difference between water and land temperature.Their cooling range is basically the same as planar water,ranging from 120 m to 150 m.The proportion of hardened surface is positively correlated with the mean temperature of water and negatively correlated with the temperature difference between water and land,while the green space proportion account for the opposite performance.On a smaller scale,the section line temperature from the field measurement indicates: the surface temperature is affected by land cover greater than nearing water.Asphalt road and cement embankment is a typical high temperature area,and the temperature of the grass is very unstable.Due to a lot of shadows,the dense woods have the most obviously cooling effect.The water bodies' temperature are low and stable,but have limited impact on the surroundings.