Layer clouds tend to cover large areas and are indicated on a satellite picture by an area of uniform brightness. This type of cloud is formed by a large-scale rising motion in the atmosphere, often associated with depressions or fronts. Convective clouds are usually formed by air being heated from below. The rising air generates cloud with the surrounding descending air being cloud-free. The individual clouds can be identified on a satellite picture, and it is sometimes possible to look at the build-up of thunderstorm cells.
Satellite pictures are particularly helpful in locating depressions and fronts.
An image can be put inside a clear plastic wallet, or under a sheet of acetate, with students being asked to mark where the fronts are likely to occur. Afterwards, the students can check their results with a synoptic pressure chart from a web site or broadsheet newspaper. Depressions can be picked out by their distinctive swirl of cloud, and frontal systems can often be seen as a wishbone-shaped area of cloud radiating from a depression. A cold front is often clearly shown as a distinctive trailing edge of the left-hand prong of the wishbone pattern. Once again, lessons can be enhanced by showing the students the satellite picture with the synoptic chart.