In what season does the topographic inversion in Sichuan Basin appear? Why?

what is inversion?

the atmospheric temperature decreases with the increase of altitude, but under some weather conditions, the atmospheric structure above the ground will have an abnormal phenomenon that the temperature increases with the increase of altitude, which is called "inversion" in meteorology.

Classification of inversion:

Generally, inversion is classified according to different causes, as follows: radiation inversion, advection inversion, topographic inversion, subsidence inversion inversion and turbulent inversion.

Terrain inversion refers to the formation of inversion in low-lying areas (valleys and basins) due to radiation cooling, and the cold air sinks along the slope and flows into the low-lying areas, which is called terrain inversion. ? Terrain inversion is mainly caused by topography, mainly in basins and valleys. Because of the rapid heat dissipation on the hillside, the cold air sinks to the bottom of the valley along the hillside, and the original warmer air at the bottom of the valley is pushed up by the cold air, resulting in the inversion of the temperature.

subsidence inversion phenomenon is more likely to occur in mid-latitude areas. At latitude 3, dry air sinks, compresses and heats itself, with more sunny days and less rain. After self-heating, the temperature is higher than that of the lower air, which is more likely to lead to inversion.

Causes and seasons of inversion in Sichuan Basin:

Sichuan Basin is located in the mid-latitude region of the south-central Asian continent (between 28 "1 ′ and 32.25 ′ north latitude), which is easily caused by topographic inversion and subsidence inversion. Inversion usually occurs in the winter half year, because the ground heat expenditure is far greater than the income at this time.

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