Why were the sands of Algeria and Saudi Arabia covered with white snow last January?

All climate models indicate that global climate change is leading to more unpredictable weather patterns.

In the Sahara and the Arabian Peninsula, the driest regions in the world and where drops of rain are an important event, snow fell last January to cover the golden sands in an unusual white color. What happens to the climate? Does this have anything to do with global warming?

In the penultimate week of last January, the desert sands surrounding the city of Al-Ain Al-Safra, western Algeria, took on a bright white suit, in a rare sight, after the temperature dropped to about 3 degrees below zero, according to a report published on the Daily Mail website. Mail).

The city, located at an altitude of about a thousand meters south of the Atlas mountain range, is called the "Gate of the Desert", and in the past it witnessed a record temperature of 58 degrees Celsius, with an average usually exceeding 38 degrees during the summer.

In the same month, the Badr region, southwest of Madinah and other regions in northern Saudi Arabia, witnessed snowfall and hailstorms, following an exceptional cold wave, as a result of which golden sand dunes were covered with white snow. The Asir region in Saudi Arabia also witnessed the first snowfall in half a century.

Although snowfall in the desert is unusual, it is not the first of its kind. The event witnessed by Ain Sefra in Algeria is the fourth in the past 42 years. Ain Sefra and some other areas of northwestern Algeria saw up to 40 centimeters of snow in 2018, and the blizzard that hit there in 2016 left more than a meter of snow, and something similar happened in 1979.

Many regions in the Arabian Peninsula have also known this phenomenon during the past years, the most recent of which was the previous year in the Qassim region and other regions of Saudi Arabia.

How is snow formed in the most hot regions of the world?

According to Casper Knight, professor of geophysics at the University of the Witwatersrand in South Africa, two factors are needed for snow to form, namely cold temperatures and moist air. This is in addition to the effect of the movement of air masses in the atmosphere and the nature of the Earth's surface on which snow falls.

Although the Sahara Desert usually experiences very high temperatures often exceeding 50 degrees Celsius, low temperatures are also recorded, especially at night due to the bare surface of the earth and the clear sky.

The snow cover around the Algerian city of Al-Ain Al-Safra was about a meter thick in 2018 (Shutterstock)

For example, very low temperatures of minus 14 degrees Celsius were recorded in Algeria in January 2005, Knight said in a recent article on The Conversation.

Winter air circulation patterns draw cool, moist air north of the Sahara from the Atlantic and Mediterranean. This results in an increase in winter precipitation along the edge of the desert in this season.

Cold air masses reach Saudi Arabia by moving clockwise from Central Asia, picking up moisture on their way, according to the Daily Mail.

The rising air can cool and condense over higher ground, such as the Atlas Mountains of Morocco and Algeria, and the highlands of Tabuk and Asir in the Arabian Peninsula. If the air is cold enough, its moisture freezes, forming ice crystals that eventually form a snow cover, and if the surface of the earth is also cold, the snow continues and does not melt immediately.

Desert and climate change

And in answer to the question: Is snow in the desert becoming more or less common? In his article, Knight says the answer is still inconclusive. This is partly due to a lack of data on past events, but also because climate models do not focus on the desert.

On the other hand, the vast area of ​​the desert allowed the use of satellites to map the distribution of rainfall and snowfall. Since this type of data was not available before, there was very little evidence of snowfall patterns before satellite records became available in the 1970s.

So desert snowfall may have historically been more common than we think. It would be interesting to use anthropological evidence and oral history to explore this possibility. Meanwhile, all climate models indicate that global climate change is leading to more and more unpredictable weather patterns.

It is noteworthy that over recent decades the size of the desert itself has also increased due to drought, and this is likely to continue in the coming decades, according to the researcher.