The dry regions or deserts found in and about 30° north and south of the equator are called the subtropical deserts. They are predominantly found in between 15° to 30° north and south of the equator where it is called the Tropic of Cancer in the north and Tropic of capricorn in the south of the equator. In these regions the air masses travels in the circular patterns, which is the main cause of hot and dryness in these regions.
Near the equator the hot air rises and as it raises it cools down and drops its moisture in the form of rain near the equator. Thus now the drier air moves away from the equator towards the Tropics of cancer and the tropic of capricorn and thus it descends down and becomes hot again. As the air lowers down it becomes difficult to form cloud and thus there is little rainfall in these area making it hot and dry. Thus they formed subtropical deserts.
