The picture illustrates how a kind of desert called the rain-shadow desert forms.
Overall, there are seven stages involved in the forming of a rain-shadow desert. The whole process starts from the sea, and ends on the island.
First, winds from the sea approach the coast and are pushed upwards when they reach the mountains. As the moist air rises along the windward side, it gradually becomes cooler. When it reaches a higher altitude, clouds form and rain begins to fall on the windward side of the mountains. Therefore, a large amount of moisture is lost before the air passes over the mountain.
After the rainfall, the air becomes dry and continues over the mountain towards the leeward side. It then moves down the mountain and becomes warmer as it reaches the lower areas. Finally, the dry winds continue towards the inland areas, where very little rain falls. As a result, the land on the leeward side becomes extremely dry, leading to the formation of a rain-shadow desert.