March 2022: A strange month in the Atacama Desert

The Atacama desert is one of the driest places in the world. However, most of March 2022 experienced humidity, clouds, and even rainfall. You don’t believe us? Here, we collected some evidence of this strange month in the Atacama.

Rainfall bands observed between Salar de Huasco and Pica, Tarapacá Region, Chile. The photo was taken by the PhD student Bárbara Vargas-Machuca, on March 9, 2022, during an excursion funded by the Collaborative Research Center 1211: Earth – Evolution at the dry limit.

In the middle of this dry desert, rain bands were observed on March 9 2022, near a location called Pica (20ºS, Tarapacá Region), around 1100 m above sea level and in the core of the Atacama. During that day, between 0.8 and 5.2 mm were recorded across the desert in different weather stations, with some thunderstorms, showers, drizzle, and plenty of clouds.

On March 16 2022, storms developed once again in the Atacama, this time near the major city of Calama (22.5ºS, Antofagasta Region), producing heavy rainfall, floods, and some damages on houses and roads. In less than 2 hours, rainfall accumulated between 1.2 and 7.2 mm in the city. The next pictures were taken at the city airport (El Loa) and show the presence of a huge convective system (left) and rain bands (right). In fact, the roof of the city airport was damaged due to the downpour.

Storm developing close to El Loa Airport at 22:20 UTC on March 16, 2022. Source: DGAC.

The next day, on March 17 2022, new storms developed with even more intense rainfall, accumulating up to 15 mm near the city of Diego de Almagro (26ºS, Atacama Region). However, the story does not end here. In addition to the thunderstorms, a huge sandstorm was observed crossing the Atacama valleys, engulfing several towns (see the next picture) and capturing the attention of the whole country. Even more unusual than rainfall, sandstorms of this magnitude are rarely seen in the Atacama.

Sandstorm approaching Diego de Almagro on March 17, 2022. Source: @radiocoquimbo

We know that any kind of storms and rainfall are originated from water vapor. Because the Atacama is so dry in terms of humidity, we usually don’t observe any hydrometers in its inner core. However, the events described in this post highlight the presence of more humidity than normal. What we do not know in this matter, for example, is how much water vapor excess was observed? Why the month of March 2022 was more humid than expected in the Atacama? Where does this humidity come from? How the humidity is spread in the desert and interact with the topography? Thus, some questions remain unanswered yet, but future works in our working group will try to unravel this mystery.

Amazon Basin waters the driest desert on Earth

The Atacama Desert is the driest place on Earth aside from the poles with annual rain rates below 2 liters per square meter. For comparison, Cologne, Germany, receives around 800 liters of precipitation per square meter each year. The water delivered to the Atacama through the very rare rain events takes a surprising path. It originates from the moisture pool above the tropical rain forest of the Amazon Basin, travels more than 2000 km including a crossing of the Andes and reaches the Atacama from the northwest.

The Atacama Desert is the driest place on Earth aside from the poles. Enduring dryness conserves traces of surface alterations over thousands of years. Photo: Jan Schween
My research goal is to determine atmospheric water supply mechanisms which feed this unique ecosystem. This will help to determine the thresholds of life at the dry limit and is important to recreate climate history.

The water is transported in filamentary structures at roughly 4 km height which are called moisture conveyor belts. These weather phenomena cause about 40% to 80% of the total precipitation in the Atacama. About four moisture conveyor belts make landfall along the coast of the Atacama each year. While some bring only very little precipitation to a limited region, some can result in strong flooding events or trigger major biological outbursts. For instance, in June 2017 a moisture conveyor belt brought over 50 liters of rain per square meter which exceeds the tenfold annual rate. In other words, it is a decade worth of rain within a couple of hours. A few weeks later, the spectacular blooming desert enchanted scientists and tourists.

Such extreme events typically leave traces in the landscape for thousands of years. The findings of our study will affect the interpretation of geological archives which reflect on such traces. The improved understanding of current water supply mechanisms will help to reconstruct climate history more genuinely which is one of the major goals of the Collaborative Research Center 1211: Earth – Evolution at the dry limit.