radiationInversionIt refers to the loss of heat at night due to the strong radiation from the ground (snow or ice surface, top of cloud layer, etc.), which makes the air layer close to it cool down more than the upper air, thus forming a phenomenon that the temperature increases with height.The heat lost on the ground gradually increases with the depth of night, and the inversion layer thickens. After sunrise, the ground gradually warms up, and the inversion layer gradually disappears.The radiation inversion is visible in the mainland all the year round, with the strongest in winter and weaker in summer.
Forming conditions
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On a clear and cloudless night, due to the strong effective radiation on the ground, the air layer close to the ground cools down quickly. The air layer far away from the ground is less affected by the ground and cools down, so there is a temperature inversion phenomenon of warming up and cooling down.With the groundEffective radiationThe continuous development of,Inversion layerGradually thicken, reaching the maximum thickness at dawn;After sunrise, with the gradual increase of solar radiation, the ground soon warms up, and the near surface gas layer begins to warm up due to the influence of the ground, so the inversion disappears from bottom to top.The vertical thickness of the radiation inversion layer can range from tens of meters to three or four hundred meters, and the temperature difference between the upper and lower boundaries is usually several degrees.
Radiation inversion often occurs on the continent in middle and high latitudes, especially in desert areas. It is strongest in winter, and the inversion layer is thick, up to hundreds of meters, and disappears slowly.In summer, it is the weakest, thinner and disappears quickly.In valleys and basins, because the cooling air also flows into valleys and basins along the slopes, the radiation inversion of valleys and basins is often strengthened, and often lasts for several days without disappearing[1]。
In winter, the mainland washigh pressureControl: due to long-term radiation cooling, the temperature of the ground and near stratum air drops significantly, which can form a winter radiation inversion. This inversion does not disappear in the daytime. The thickness of the inversion layer can reach hundreds to thousands of meters, and the temperature difference between the upper and lower boundaries can reach 15 to 25 ℃, sometimes lasting for several days.
Favorable conditions for forming radiation inversion: sunny, cloudless and breezy (2-3 m/s) nights.Because clouds can weaken the groundEffective radiation, which is not conducive to ground cooling.When the wind is too strong, the vertical mixing effect in the atmosphere is too strong, which is not conducive to the cooling of the near surface gas layer. When there is no wind, the cooling effect cannot extend to the higher gas layer, which is not conducive to the thickness of inversion. Appropriate wind speed is not only conducive to the formation of a certain thickness of inversion layer, but also will not cool the near surface gas layer due to strong mixing.
