Why are some deserts cold?

Cold deserts, such as the Gobi Desert, are places with little rain and low temperatures in winter due to geographical features.

The McMurdo Dry Valley in Antarctica has not had rain for about 2 million years. Photo: NASA/GSFC/METI/ERSDAC/JAROS/ASTER Science Team

When talking about the desert, many people will imagine hot sand dunes and scorching Sun. However, this is only one aspect of the desert climate. Besides the Sahara and the Great Australian Desert, some desert environments are associated with more cold temperatures.

Deserts are defined as areas that receive very little precipitation and are not necessarily related to temperature. Many deserts are extremely hot with daytime temperatures reaching up to 54 degrees Celsius, but temperatures drop very low at night due to lack of moisture and poor heat retention properties of sand.

Some deserts are cold for long periods of time day or night. Scientists simply call these places cold deserts. Unlike hot deserts, cold deserts are often located around temperate regions at high altitudes, for example on plateaus or between mountain ranges. They are often located deep inland, separate from coastal waters - a factor that causes air humidity to increase.

The Gobi Desert in northern China and southern Mongolia is one of the most prominent examples. Summers here are very hot, but winter temperatures can remain at -38 degrees Celsius. One reason this desert is so cold is its high latitude, and is located on a plateau above the water level. The sea is about 910 - 1,520 m. The dryness of the Gobi Desert is caused by the rain shadow effect. South of the desert is the Himalayas, a mountain range that blocks moisture-rich clouds coming from the Indian Ocean.

Another example is the Patagonian, the largest desert in Argentina. It is relatively warm in the summer, but in the winter the temperature rarely exceeds 12 degrees Celsius and the average is only 3 degrees Celsius. The US also has cold deserts, for example the Great Basin Desert in the mid-Sierra Nevada and the Wasatch Range.

Some areas of the Arctic and Antarctic are classified as polar deserts. In fact, the Antarctic Polar Desert is the largest desert in the world, typically receiving less than 50 mm of rain per year, most of which falls as snow or ice crystals. Polar deserts don't get much rain because the cold temperatures don't hold as much water vapor, leading to less humidity and a low chance of rain.

Antarctica is also the driest continent on the planet. Some of the driest areas in Antarctica, called dry valleys, have not received any rain for about 2 million years. Along with the continent's extreme temperatures, this exceptionally dry condition is also caused by the surrounding barrier mountains. Despite this climate, the dry valleys still have life. However, there aren't any seals or penguins here. The rare life forms that exist here are lichens, mosses, algae and cyanobacteria.