Arid climates, known for their extreme dryness, cover approximately one-third of Earth's land area. They are most commonly found between 30 degrees north and south of the Equator due to global wind patterns, but arid conditions can also occur in other regions, such as the rain shadows of large mountain ranges or continental interiors. Arid climates are generally classified into two types based on temperature: hot deserts and cold deserts. Hot deserts, or "hot arid subtypes," have average annual temperatures above 18°C (64.4°F). In contrast, cold deserts, or "cold arid subtypes," experience temperatures below this threshold.
Weather patterns in arid climates
Arid climates are defined by their exceptionally low rainfall, typically receiving less than 10 inches (250 mm) annually. For instance, the Atacama Desert in Chile is one of the driest places on Earth, with annual precipitation as low as 0.04 inches (1 mm). Even areas with slightly higher rainfall, such as parts of Central Australia and the Sahel in Africa, are considered arid due to their high evaporation rates. Temperature extremes are common in arid regions: hot deserts can reach up to 130°F (54°C), while cold deserts may experience temperatures as low as -30°F (-34°C). These temperature variations are influenced by the desert's distance from the equator.
Hot desert climates
Hot desert climates, characterized by extreme heat and dryness, are typically located under the subtropical ridge between 20° and 33° latitude in both hemispheres. These regions experience high atmospheric pressure and stable descending air. Hot deserts are found across various continents, including Africa, Asia, Australia, and the Americas, but they are absent from Antarctica. In summer, these deserts experience extreme heat, with average temperatures ranging from 84°F to 95°F (29°C to 35°C), and midday temperatures often reaching 109°F to 115°F (43°C to 46°C). The highest recorded temperatures on Earth, exceeding 122°F (50°C), occur in these deserts, such as the 134.1°F (56.7°C) recorded in the Death Valley. Some tropical deserts maintain very high temperatures year-round, with annual averages surpassing 86°F (30°C) and reaching up to nearly 95°F (35°C) in places like Dallol, Ethiopia. Night-time temperatures can drop to freezing or lower due to significant radiation loss under clear skies, though extreme cold is rare. Notable hot deserts include the Sahara and Libyan Deserts in North Africa, the Arabian and Syrian Deserts in West Asia, the Thar Desert in South Asia, and the Mojave and Sonoran Deserts in the United States and Mexico. In Australia, the Simpson and Great Victoria Deserts are prominent, while in Europe, only southeastern Spain and a small part of the Tabernas Desert experience this climate. Hot deserts are among the hottest, driest, and sunniest places on Earth due to their constant high pressure, limited atmospheric disturbances, and high solar exposure, making them inhospitable to most life forms.
Cold desert climates
Cold deserts are large arid regions characterized by scarce annual precipitation, which predominantly occurs as snow or fog. Typically, these areas receive less than 25 cm (about 9.8 inches) of precipitation per year, though this amount can vary. Cold deserts are commonly found in high-elevation temperate regions, plateaus, or mountainous areas, and also appear in polar regions. They have colder temperatures compared to hot deserts, particularly in winter, and feature limited vegetation, mostly shrubs and grasses. Flora and fauna in these regions have developed adaptations to survive harsh, frigid conditions. Key examples include Central Asia, western North America, parts of South America, Antarctica, and the Arctic. Polar deserts, a subset of cold deserts, are found in the Arctic and Antarctic regions. These areas are extremely cold with minimal precipitation, featuring long, frigid winters and very short, cool summers. In the Arctic, permafrost and snow cover dominate, while Antarctica is largely covered by ice sheets. Despite the extreme conditions, some hardy species of plants and animals have adapted to these environments, including various mosses, lichens, and extremophile microorganisms. Notable examples of cold deserts include the Gobi Desert in Asia, known for its extreme temperature variations between summer and winter, and the Great Basin Desert in North America, characterized by snow precipitation and unique flora like sagebrush. Patagonia in South America and parts of the Arctic and Antarctic regions also exemplify cold desert environments. The Arctic polar desert, found in northern regions like Canada and Russia, supports a surprising amount of biodiversity, while the Antarctic polar desert, covering most of Antarctica, is more sparsely populated but still supports specialized life forms such as psychrophiles and certain cold-adapted mammals and birds.
Plant and animal life
In arid climates, such as deserts, vegetation is scarce due to the extreme dryness. While some arid regions, like the Atacama Desert, are so dry that plant life is almost nonexistent, other arid areas do receive minimal rainfall, up to 10 inches annually. Plants in these environments have adapted to conserve or require very little water. Common adaptations include long roots and thorns. Typical vegetation includes scrub bushes, grasses, and cacti. Similarly, animal life in arid climates has evolved to handle the harsh conditions. Animals like camels are specially adapted to store water in their bloodstream and can consume up to 40 gallons of water in a short period, allowing them to endure long periods without hydration. Foxes and jackals are also prevalent in desert regions, along with reptiles like the Sidewinder snake and arachnids such as scorpions, all of which have developed unique adaptations to survive the extreme heat and limited water supply.
Test your knowledge
What is the typical annual precipitation threshold that defines an arid climate?
