Final answer:
Subtropical regions around 30 N and 30 S are dominated by high pressure, resulting in very dry conditions with evaporation exceeding precipitation, and extreme temperature variations between day and night.
Step-by-step explanation:
In the subtropical regions (around 30 N and 30 S), the area is dominated by high pressure. The Sahara Desert in northern Africa and the Namib Desert in southwestern Africa are examples of deserts that exist because of the high-pressure, dry air descending at those latitudes. These subtropical deserts are characterized by very dry conditions, where evaporation typically exceeds precipitation, and they experience extreme temperatures that can soar above 60°C (140°F) during the day and plummet to about 0°C (32°F) at night.
This high-pressure system is part of the Earth's global wind circulation pattern, contributing to the aridity of these regions as descending air warms and can hold more water vapor, leading to dry conditions. Consequently, these regions have low annual precipitation of fewer than 30 cm (12 in), with little monthly variation and an unpredictable rainfall pattern. The lack of water vapor in the air is also responsible for the significant temperature drops during the night.