Cooling Regularity Of Urban Cold Island On Thermal Environment Of Surroundings

With the development of urbanization,the impact of Heat Island Effect is becoming more and more severe.But there are still existing low temperature areas in the city to offer cool and comfortable environment to the people.This paper extract the green,water and impervious surface to get the underlying structure within the Fifth Ring Road in Beijing.Mono-window algorithmis used to measure the surface temperature,and the actual surface temperature is tested.This paper analysis the thermal landscape pattern in Beijing within the fifth ring to get screened 30 block cold island areas.This paper analyzes the influence factors of the internal temperature of the cold island area and the influence factors of the cold island on the surrounding thermal environment.In the end,we concluded as below:(1)The average temperature of the cold island within the city does not change significantly with the change of plaque morphological characteristics of cold island.The minimum temperature in the cold island decreases with the increase of the patch area and perimeter of the cold island,and increases with the increase of the shape index.The average temperature inside the cold island does not change significantly with the change of the cold island landscape constitute.The minimum temperature decreases gradually with the increasing of green space and water area,but the minimum temperature does not change with the increasing of the rate of construction.(2)Cold island external temperature increases with the increasing of the distance,and then tend to be stable,at this time,the temperature is the maximum temperature around the cold island,the distance of the place with maximum temperature to the cold island boundary is the maximum cooling distance.Through the cubic polynomial fitting,the paper has built model to determine the cold island cooling rate and cooling distance.(3)Temperature drop and cooling distance increase with the increasing of Cold Island City area and perimeter and decrease along with the green cold island shape indexincreasing.Temperature drop and cooling distance increase gradually with the increasing of green space and water area,but the temperature drop does not change with the increasing of the rate of construction,the cooling distance decreases with the increasing of the rate of construction.(4)This paper analyzes the influence of construction land on the building index,building height and building layout.The higher building index means the higher building density,the construction land becomes warming faster and the cold island cooling is greater.With the building height increasing,the building environment warms up more quickly.When the building height is more than 100 m,the heating rate declines.Using the layout of the building angle,the cooling effect of cold island has a barrier effect,which is conducive to disperse cold air with building channels.