Anthropogenic cloud
The intermediate layers of the troposphere are the regions with less influence of human activity. This region is far enough from the surface for not being affected by the surface emissions. Additionally, commercial and military flights only cross this region during ascending or descending maneuvers. Moreover, in this region there exist two types of clouds with a large horizontal extension: "Nimbostratus" and "Altostratus", which cannot originate from human activity. Consequently, it is assumed that there are no anthropic clouds of these two "genera". However, what can occur is enhancing existing "Nimbostratus" or "Altostratus" due to the additional water vapor or condensation nuclei emitted by a thermal power plant, for instance.
Col (meteorology)
In the real atmosphere, highs and lows have rarely the same strenght and thus equal wind flow pattern around them. Thus the advection of warm or cold air is rarely equal. Furthermore, their shape and position are rarely as perfect as in the illustration quadrants either. There are thus 3 types of saddles or cols: the symmetrical, the cyclonic and anticyclonic.