2.5 Air circulation
At this stage, air circulation enters and plays a dual role. Firstly, winds transmit moisture horizontally from one location to another. In this way, moisture derived from oceanic evaporation can be transported many miles to a land mass. Secondly, convective or vertical currents arising from unequal heating or cooling can transmit moisture upwards. When it cools, some of the water vapour condenses. It is from these currents that most precipitation develops.