Study On Transmission Performance Of Infrared Radiation Energy From Urban Underlying Surface In Atmospheric Window Area

With the rapid development of the economy,China's urbanization process has been accelerating.By the end of 2017,the urbanization rate of China has reached 59.58%.The rapid growth of urbanization has brought about many ecological and environmental problems to the city.Among them,urban thermal environment problems characterized by heat island effect are particularly prominent.People's living environment and quality of life are affected and the sustainable development of city are also restricted by the quality of urban thermal environment.Therefore,research on methods of urban thermal environment improvement will help to maintain urban ecological balance and ensure the coordinated development between human and nature.A number of solutions based on the causes of urban thermal environment problems are proposed in recent years,which are mainly related to greening layout,water planning,urban planning,application of porous materials,application of cooling materials.However,these measures have certain limitations,which are mainly to focus on reducing the underlying surface temperature by changing the form of heat or transferring heat,but less on changing the total heat in the environment.Therefore,it is necessary to explore new methods to control urban thermal environment.The energy influencing the urban thermal environment mainly comes from infrared radiation heat transfer,which caused by the urban underlying surface absorbing solar radiation.In consideration of the above fact,the research,which combines the principle that emitted infrared energy of the urban underlying surface are mainly in the 5.970~17.701?m and emitted infrared energy of 8~14?m can penetrate the atmospheric infrared window into the outer space,on the more effective way to regulate urban thermal environment is conducted in this paper by investigating and controlling infrared radiation heat transfer between the underlying surface of the urban area and the outer space in Chongqing area.Firstly,the mathematical model of the calculating analysis of infrared energy emitted from different ground objects and atmospheric transmittance in the troposphere was established.Six kinds of urban ground objects(soil,brick,asphalt,sandstone,marble and white ceramic tile)are selected as the research objects.Based on the spectral data of ground objects and relevant parameters obtained from experiments,infrared energy emitted from different urban ground objects in 8~14?m under the actual weather conditions and atmospheric transmittance of which in water vapor and carbon dioxide of the tropospheric are calculated,and then the infrared energy penetrating the atmosphere of the atmosphere infrared window in the 8~14?m are determined.The results show that:(1)Affected by the urban surface temperature,emissivity and radiation wavelength,the infrared energy penetrating the atmosphere is determined not only by atmospheric transmittance,but also by the distribution of infrared energy emitted from different urban ground objects.(2)When the emitted infrared energy is assumed to be horizontally distributed,the infrared energy penetrating the atmosphere is only determined by atmospheric transmittance.(3)Because of the non-uniform distribution of emitted infrared energy along the wavelength,in the case of the same emitted infrared energy,priority should be given to materials with large emitted infrared energy distribution in the waveband with high atmospheric transmittance,which can release more emitted infrared energy to outer space.Then,according to the influence of water vapor on the absorptivity of the atmospheric infrared window(AAIW)in the 8~14?m,the parameters required for AAIW calculation and analysis are determined by field experiments of the six urban ground objects mentioned above,and the AAIW mathematical description based on water vapor distribution is established.The distribution of AAIW in Chongqing is analyzed by using the mathematical description and the annual meteorological data in Chongqing.By comparing the annual distribution of temperature and AAIW,the internal relationship between urban thermal environment and AAIW is analyzed,and the mechanism of AAIW effect on urban heat island is revealed.The results show that:(1)The AAIW mathematical description based on water vapor distribution proves that AAIW is significantly correlated with water vapor,which provides a convenient tool for further study on the distribution of AAIW.(2)AAIW increases with the increase of temperature,which reveals the important contradiction between urban thermal environment and AAIW.When the temperature is higher in summer,AAIW is higher,which results in that the infrared energy emitted from different urban ground objects can not be released to the outer space very well.When the temperature is lower in winter,AAIW is lower,but it can release more emitted infrared energy to the outer space.(3)Urban heat island effect will lead to more emitted infrared energy absorbed by urban atmosphere than in rural areas,and additional infrared energy absorbed will further deteriorate the urban thermal environment.At last,the surface temperature,solar radiation intensity,near-surface wind speed and atmospheric pressure,air temperature and humidity of eight kinds of surface materials at different dates and different times are measured and calculated hourly.The annual variation of atmospheric window transmittance,emitted infrared energy,infrared energy penetrating the atmosphere and infrared energy absorbed by the atmosphere of different ground objects in 8~14?m waveband under actual atmospheric conditions are analyzed.Thus,the transmission rule of infrared radiation energy of underlying surface in the atmospheric window area is revealed.The results show that:(1)The material properties of different objects and solar radiation intensity are the important reasons for the difference of infrared energy emitted from different ground objects.(2)At different times,the transmittance of atmospheric infrared window is basically the same as that of radiation wavelength.The maximum transmittance ranges from 10.4~10.8?m and the minimum transmittance ranges from 13.4~14?m.(3)The penetrated energy is the highest in winter,the middle in spring and autumn,and the lowest in summer.While,the infrared energy absorbed by the atmosphere is the highest in summer,the middle in spring and autumn,and the lowest in winter.