Population movements around the Chinese New Year （CNY）, which are much larger in recent years than before, are the largest annual human migration in the world. However, it is still largely unknown how or to what ext...Population movements around the Chinese New Year （CNY）, which are much larger in recent years than before, are the largest annual human migration in the world. However, it is still largely unknown how or to what extent such mass human migration affects urban climate. Here, we investigate the role of mass human migration in influencing Beijing＇s urban heat island （UHI） during the CNY holiday for the period of 2004-2013. We find that the UHI effects expressed as daily mean （ATmean）, maximum （ATmax）, and minimum （ATmin） temperature differences between urban and rural areas show a weakening trend during the CNY week relative to the background period （4 weeks including 2-3 weeks before and 2-3 weeks after the CNY week）. In particular, large reductions occurred during the CNY week for the period of 2009-2013, when nearly half of population left the city before the CNY holiday. △Tmean, △Tmax, and △Tmin averaged over the period of 2009-2013 during the CNY week were 0.64, 0.45, and 0.83 ℃ lower than during the background period, representing relative reductions of 35 %, 66 %, and 27 %, respectively. Our findings highlight the important role of modem mass human migration for urban climate based on a case study in Beijing.展开更多
基金supported by the National Natural Science Foundation of China(41275089 and 41305071)the National Basic Research Program of China(2012CB955604)
文摘Population movements around the Chinese New Year （CNY）, which are much larger in recent years than before, are the largest annual human migration in the world. However, it is still largely unknown how or to what extent such mass human migration affects urban climate. Here, we investigate the role of mass human migration in influencing Beijing＇s urban heat island （UHI） during the CNY holiday for the period of 2004-2013. We find that the UHI effects expressed as daily mean （ATmean）, maximum （ATmax）, and minimum （ATmin） temperature differences between urban and rural areas show a weakening trend during the CNY week relative to the background period （4 weeks including 2-3 weeks before and 2-3 weeks after the CNY week）. In particular, large reductions occurred during the CNY week for the period of 2009-2013, when nearly half of population left the city before the CNY holiday. △Tmean, △Tmax, and △Tmin averaged over the period of 2009-2013 during the CNY week were 0.64, 0.45, and 0.83 ℃ lower than during the background period, representing relative reductions of 35 %, 66 %, and 27 %, respectively. Our findings highlight the important role of modem mass human migration for urban climate based on a case study in Beijing.
