Basics of Environmental Science

Earth Sciences / 67

Figure 2.22 Formation of cloud at a front. 1, Cold air is advancing rapidly,

undercutting warm air and forcing it to rise. 2, Stable warm air is advancing,

rising gently over cold air

Figure 2.23 Distribution of cloud around frontal systems. 1, The system starts to form. 2, The
two fronts are still separate. 3, Warm air is rising over cold air. 4, The fronts are almost fully
occluded. 5, Cloud distribution around a low-pressure centre