Assessing Heat Wave Risk In Beijing By Multi-source Remote Sensing

Under the background of global warming,rapid urbanization and unbalanced social development,the impact of high temperature heat wave on the health and social economy of urban residents is growing,and it has become one of the most important meteorological disasters facing cities.Based on multi-source information such as meteorological observation data,AQUA/MODIS surface temperature products,NPP/VIIRS nighttime data and social statistics,this paper constructs risk,exposure and vulnerability assessment indicators to quantitatively calculate the risk of heat wave in Beijing.Based on the correlation between the AQUA/MODIS surface temperature and the maximum daily temperature of the site observation during the high temperature heat wave period,the daily maximum temperature was estimated from the remote sensing surface temperature,and the average daily maximum temperature and high temperature duration days were calculated as the high temperature heat wave risk assessment factors.By using NPP/VIIRS night light data,land cover data,population statistics,etc.,the Random Forest algorithm was adopted to downscale Beijing population statistics data to obtain the population density map with spatial resolution of 500 meters,which combined with vegetation index,building index and water body index to form the assessment factors of high temperature heat wave exposure.The proportion of elderly population,construction workers and air conditioning ownership rate were extracted from social statistics as vulnerability assessment factors.Using expert evaluation method and entropy weight method,the combination of subjective weighting method and objective weighting method is realized to obtain comprehensive weights which are applied to calculate the risk of heat wave in Beijing.Quantile classification method and natural break point method are used to classify the risk of high temperature heat wave,which is divided into ten levels.The spatial distribution characteristics and influencing factors of high temperature risk in Beijing were comprehensively analyzed,and the risk of high temperature heat wave in Beijing was comprehensively evaluated.The results showed that:(1)The risk distribution of high temperature in Beijing has significant spatial difference.With the second ring as the center,it shows a circular decreasing trend around,forming the largest risk coverage area,and forming multiple risk sub-centers in the main urban area of each area;(excluding the historical and cultural scenic spots of the Palace Museum and the surrounding scenic spots)(2)The historical and cultural scenic spots of the Palace Museum and the surrounding scenic spots within the Second Ring Road have low risk,which makes them the low risk Valley in the Second Ring Road,and can be used as the place for emergency cooling in the city.(3)In addition to the central urban areas and the urban areas of each district,the risk levels of Yanhuai Basin,Miyun Valley and some plains in the eastern part of Pinggu in the southwest of Yanqing District are also relatively high.(4)In plain area,the risk of Xicheng District and Dongcheng District is the highest,followed by Shijingshan District,Fengtai District,Haidian District and Chaoyang District.(5)Generally speaking,the risk distribution in the north of the city is lower than that in the south,and that in the west is lower than that in the east.The high-risk areas are mainly concentrated in the central city and suburbs of the Sixth Ring Road,while the high-temperature risk in the outer suburbs is generally low.