Eocene
Another method considered for producing the warm polar temperatures were polar stratospheric clouds. Polar stratospheric clouds are clouds that occur in the lower stratosphere at very low temperatures. Polar stratospheric clouds have a great impact on radiative forcing. Due to their minimal albedo properties and their optical thickness, polar stratospheric clouds act similar to a greenhouse gas and traps outgoing longwave radiation. Different types of polar stratospheric clouds occur in the atmosphere: polar stratospheric clouds that are created due to interactions with nitric or sulfuric acid and water (Type I) or polar stratospheric clouds that are created with only water ice (Type II).
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.