| environ. | atmospheric inversion A temperature inversion in the atmosphere in which the temperature, instead of falling, increases with height above the ground. With the colder and heavier air below, there is no tendency to form upward currents and turbulence is suppressed. Inversions are often formed in the late afternoon when the radiation emitted from the ground exceeds that received from the sinking sun. Inversions are also caused by katabatic winds, that is cold winds flowing down the hillside into a valley, and by anticyclones. In inversion layers, both vertical and horizontal diffusion is inhibited and pollutants become trapped, sometimes for long periods. Low-level discharges of pollutants are more readily trapped by inversions than high level dischargers, hence the case for high stacks. Furthermore, high level discharges into an inversion tend to remain at a high level because of the absence of vertical mixing | 大气倒置 (大气中的温度倒置，在这种状况中，气温随着海拔的增加不减反增。由于下面更重更冷的空气，没有形成上升气流的趋势，湍流也被压制。倒置通常在下午晚些时候形成，这时候地面发出的射线超过了接收的来自下沉太阳的射线。倒置也会由下降风引起，这种风会以反气旋的形式从山上吹到山谷里。在倒置层，污染物的水平和竖直扩散都会被抑制从而被困住，有时会持续很长时间。低处的污染物放电比高处的更容易被倒置困住。而且，高处的污染物向倒置大气放电仍会保持在高处，因为缺少竖直混合。) |