The effects of human movements on urban climate over Eastern China

We live on an urban planet with unprecedented human mobility. In this study, we collectively analyze ten large cities over densely populated Eastern China, and detect that mass people outflows during Spring Festival (SF) holiday significantly cool down urban climate expressed as urban heat island intensity variation particularly at the nighttime after minimizing the effects of other factors. We estimate that the average nighttime cooling effects of the ten large cities over Eastern China during the SF holiday relative to the nearby background period are 0.63 degrees C stronger during the 2000s than during the 1990s. The attribution analysis points to that the urban cooling effects are primarily caused by mass people outflows during the SF holiday. Our findings help to better understand the complex interactions of human population dynamics, urban development, and the environment, and may have important implications for promoting sustainable, people-centered, and resilient development of our urban planet.