Final answer:
Subtropical deserts form due to high-pressure dry air descending in specific latitudes, which leads to minimal precipitation, and cold ocean currents can exacerbate this aridity. The formation of some deserts is influenced by mountains that create rain shadows, while others are directly impacted by latitudinal high-pressure systems.
Step-by-step explanation:
Subtropical deserts:
The primary cause of subtropical deserts is the descending high-pressure dry air at particular latitudes, resulting in very little precipitation. These regions are between 15° and 30° north and south latitude, near the Tropic of Cancer and the Tropic of Capricorn. Cold ocean currents along the coast can intensify the dryness by cooling the air and decreasing its ability to hold moisture, which contributes further to the lack of rainfall.
For instance, the Mohave and Sonoran deserts are shaped by rain shadows created by mountain ranges blocking moisture-laden winds. In contrast, deserts like the Sahara and the Namib are directly influenced by the high-pressure systems typical at those latitudes, causing evaporation to exceed precipitation. Such deserts experience extreme daily temperature variations due to the lack of moisture in the air, leading to high daytime temperatures that can exceed 60°C (140°F) and nighttime temperatures that approach freezing.