In wintertime, a temperature inversion occurs when cold air close to the ground is trapped by a layer of warmer air. As the inversion continues, air becomes stagnant and pollution becomes trapped close to the ground. Therefore inversions often cause the formation of smog. However, inversions and smog do also occur in summer and might turn into a serious respiration hazard over densely populated areas.
This diagram shows how an inversion has a temperature decrease with height less than normal decreases with height.
A mixed layer of air is the surface layer of air that is turbulent and well mixed. The mixing height is the thickness (sometimes zero) of this mixed layer. Stronger wind speeds and thicker mixed layers will produce higher venting indices. Often our mixed layer is narrow and wind speed very little therefore we see lower venting indexes.
http://terrybnd.blogspot.com/2011/10/cloud-temperature-inversion-inversions.html. This dude explains “Radiation fog. Valleys with misty bottoms and Cloud Inversions.” He’s a photographer looking for the perfect inversion conditions from above. You don’t want to be in it!