Traditional Culture Encyclopedia - Weather inquiry - There is always smog in winter in the north, why is it rare in summer?

There is always smog in winter in the north, why is it rare in summer?

Because it is necessary to burn coal for heating in winter in the north, this will increase the chance of haze weather. Chengdu, located in the Sichuan Basin, is a real southern city, located in the south of Qinling Mountains. There is no central heating in winter, and even there are relatively few highly polluting enterprises. However, the probability of polluted weather in winter in Chengdu is still higher than that in summer, so heavy polluted weather always appears in winter in northern cities.

China is located in the northern hemisphere as a whole. In winter, when the direct sunlight time is shortened, the radiation received by the ground will be correspondingly reduced, resulting in obvious surface cooling. But the air far away from the ground will heat up after absorbing heat. When there is a big difference between the two, it will lead to an inversion layer at low altitude.

The inversion layer will weaken the vertical convection exchange and conversion power of air, and the polluted air can't rise further to the middle and high levels, but can only gather in the low-level layer, showing a gray and foggy picture, and finally form what we call heavily polluted weather. In other words, the inversion layer covers the city like a thick quilt, which inhibits the diffusion of pollutants such as sulfur dioxide, particulate matter and carbon monoxide, and combines with water vapor at low altitude to form aerosols.

The second reason is that there is less precipitation in winter, and the ability to "wash" air pollutants becomes weak. Because China is located on the west coast of the Pacific Ocean, under the influence of the western Pacific subtropical high and southwest monsoon, there will be intensive rainfall in summer, which can well wash away pollutants in the air and purify the atmosphere.

In winter, the northwest wind prevails in China, and the precipitation from north to south will decrease accordingly. Especially in inland cities, in the absence of effective water vapor, there is little precipitation in the whole winter. No precipitation means that pollutants in the air have been suspended, and finally there will be heavily polluted weather.

Finally, in some cities with basin topography, because the surrounding environment is closed, in the absence of effective wind blowing, pollutants emitted by motor vehicles, cross-country mobile machinery, oil trucks and industrial production will gather at low altitude, which is not easy to spread, resulting in serious air pollution, regardless of Xia Dong or north and south.