The researchers studied how energy moves in the air in a big city like Beijing. They looked at data collected from a tall tower over a year to understand the changes in temperature and heat. In the summer, there's more rain and the air feels hot, and in winter it's dry and cold. They found that in the city: summer has less hot air than winter, and the ground reflects different amounts of sunlight based on the season. During the day, a lot of the heat goes back into the air, but at night, other types of heat are released, likely from human activities. On cloudy days, there's more heat in the air, especially in winter. That's how energy flows in a big city like Beijing with tall buildings and traffic.