Geographical Location of Atacama Desert: It is located at the west coast of South America. It roughly covers whole of Chile and some parts of its neighbouring countries.

More INFO: http://arabcooking.me/usa-map-of-deserts-2.html/south-america-map-atacama-desert-maps-of-usa-new-usa-deserts

Climate:

The Desert is considered as the driest non-polar location on the Earth. The average annual rainfall is extremely low (about 14-16 mm). Even some locations in the desert have never received any rain.Researchers found that the rainfall received by the desert in the period 1570 to 1971 was close to none.

Why it is so much dry?

There are many reasons for it. Few of them are -

1) Westward side:

You can notice from the first picture that almost all important desert in the southern hemisphere lies on the westward side e.g. Atacama, Namib. The reason is the direction of winds (see the direction of Trade winds in the below picture).

The Trade winds carries moisture from the oceans and as they hit the land they start dropping it in the form of rain. But the western side is too far and when they reach there they hardly have any moisture left with them therefore they flow there as hot and dry winds.

2) Rain shadow effect

As the winds hit the mountains, it rises with the mountains resulting in clouds and rainfall on one side of mountain. Now the air advancing the other side of the mountain is hot and dry as it already had lost the moisture (shown in the figure below).

The Atacama Desert lies between the Andes mountain chains and Chilean Coast mountain Range. So, the desert is victim of 2 sided rain shadow effect.

3) Surrounded by cold ocean water:

Water near Chilli and Peru coast is highly cold. This makes the air above it highly cold. The cold air being heavy don’t rise up in the atmosphere resulting in no rainfall. Moreover, cold air can’t hold much moisture hence it results into no or less rainfall even if it rises.

Similarity with the Mars:

The soil of southern region of Antofagasta (part of Atacama Desert) is been compared to the soil of Mars. Due to uncanny resemblance of this part of land with mars it is been used to shoot Mars scene for the movies and television series (Mars scene of the Space Odyssey: Voyage to the Planets television series has been shot here). The Atacama Desert also serves as the site for a NASA-fundedproject related to Mars. It is also one of the best place to conduct astronomical observations because there is no cloud cover.

Moreover it is located far away from the populated cities resulting in very less or no radio interference.

Atacama Desert - Why it is Driest Non-polar place in the World.