The Changing Characteristics Of China's Compound Extreme Events In The Past Century And Their New Definition Combined With Health Dat

Based on the reanalysis data of CRU,NOAA and ERA-20 C,this study analyzes the change characteristics of compound extreme events(CEEs)of temperature and precipitation in China on seasonal,interannual and interdecadal scales between 1901 and 2019,and reveals the dominant factors.A new definition of CEEs which lead to human health risks is obtained by introducing the data of emergency ambulance dispatches which is closely related to human health into CEEs.The results show that the total frequency of CEEs in China in the long-term trend tends to increase.However,characteristics of the respective type of CEEs differ from those of the total CEEs.There are less CEEs but increasing warm-dry in 1901-1950.The period of 1951-1995 represents frequent cold CEEs(cold-wet and cold-dry),cold-wet are largely distributed in most areas except for northeast and coastal areas of China,and cold-dry are mainly concentrated in northwest regions of China.The period 1996-2019 contains frequent warm CEEs(warm-wet and warm-dry)and less cold CEEs,Warm-wet frequently occurs in the Tibetan Plateau and northwest China,while the warm-dry are mainly distributed in southwest China and northern China during this period.The frequency of warm-dry and cold-wet were higher than that of warm-wet and cold-dry over the past 119 years,whereas warm-wet increased fastest in the northwest region after 1996(increased more than 1month/decade in the eastern part of northwest China),consistent with the warm-wetting characteristics in the northwest region of China.In addition,the occurrence range of warmdry and warm-wet has been expanding in a north-south direction since the 1990 s.Further studies show that long-term climate change has the greatest impact on CEEs among long-term climate change,extreme changes of temperature and precipitation,and coupling changes between extreme temperature and extreme precipitation.Furthermore,dynamic factor analysis shows that the temperature rise caused by long-term climate change affects the interdecadal characteristics of CEEs in China through the changes of circulation fields such as East Asian trough and subtropical high and the configuration between them.The new definition of CEEs leading to human health risk based on emergency ambulance dispatch data makes future risk assessment more targeted and feasible.