Mapping Apparent Temperature In Beijing Based On Remote Sensing

Global warming and rapid urbanization havd brought tremendous changes in the human living environment.Under the combined effects of the“heat island effect”and other factors,the possibility of high temperature disasters in urban areas in summer is gradually increasing.The conventional air temperature indicator does not fully reflect the thermal environment pressure which effects on the human body in hot and humid summer,Apparent temperature reflects the influence that temperature and humidity act on human,which can be used to characterize the human body comfort.The apparent temperature in Beijing region was retrieved based on remote sensing data in this paper.Firstly,the temporal distribution of major meteorological elements and apparent temperature in Beijing were obtained through years of station observation data.Secondly,the environmental parameters which affecting the apparent temperature were calculated from multi-source remote sensing data,then calculated the Humidex and the Net Effective Temperature by using the empirical regression model and the random forest model.Finally,analyzed the spatial distribution of apparent temperature,compared the spatial distribution differences between surface temperature,temperature and apparent temperature,then graded the human comfort according to the Humidex in Beijing.The research main conclusions were as follows:?1?In the past 40 years,the climate change in Beijing has shown a trend of increasing temperature,dehumidification and fluctuation of wind speed.The temperature increase rate is0.33?/10a,and the relative humidity decline rate is 0.5%/10a,it?s show an obvious urban heat island characteristics in Beijing.The apparent temperature was risen slowly,the HMI increase rate is 0.33?/10a,and the NET incresase rate is 0.5%/10a The analysis shows that the trend of warming and drying in Beijing is inextricably linked to the process of urbanization,the meteorological conditions and urban structure were not conducive to heat dissipation in hot and humid summer.?2?The empirical model and the random forest model were used to calculate the humidex index?HMI?through remote sensing data.The algorithm compares found that the random forest model has better accuracy than the empirical model,the NET index acalculated by random forest model also achieved good results.?3?The distribution characteristics of HMI and NET were similar,both of them were reflected that there was significant spatial difference in summer apparent temperature which the southeast was higher than northwest and the urban higher than suburb in Beijing.However,two indicators?s range was different,the average of HMI was 35.18? and the NET is 24.9?.It also show an obvious spatial variability in the interior of metropolitan area due to the different distribution of urban functional area.The difference between the Xicheng District with the highest HMI and the lowest Yanqing District was 9?.There were eight districts?apparent temperature in Beijing exceeded 35?,reaching the high temperature level,HMI was exceed air temperature by more than 5?in these areas at same time.?4?The human comfort was graded according to the humidex in Beijing,there were.5% of the area felt comfortable,81.3% of the area was slightly uncomfortable,and 11.2% of the area was uncomfortable in Beijing on 10^th July of 2017,there were no area reached dangerous or extremely dangerous levels,but people still need to be protected against the effects of hot and humid weather.