The Sahara Desert, renowned for its barren, arid landscapes, is considered to be one of the driest places on Earth. However, NASA‘s Earth Observatory satellite images show the region is seeing a surprising burst of greenery.

Some regions in Morocco, Algeria, Tunisia, and Libya—which barely receive a few inches of rain per year—now show traces of green after an extratropical cyclone drenched parts of northwestern Sahara on September 7 and 8. The cyclone drenched large, treeless swaths of the region.

On September 10, the MODIS (Moderate Resolution Imaging Spectroradiometer) on NASA’s Terra satellite captured the false-color image of the resulting runoff and floodwater.

In the news image taken on Terra satellite, NASA combined visible and infrared light and showed areas covered by water that appeared dark and light blue. According to details, the shade of blue is influenced by the depth of the water and the amount of suspended sediment.

The same region was dry and arid in the image captured on August 14.

Earlier on August 9, France24 reported that torrential rains caused floods that killed at least 11 people and left nine still missing in Morocco’s southern provinces of Tata, Tiznit, and Errachidia. It added that the floods destroyed 40 homes, damaged 93 roads, and disrupted electricity, water supply, and phone networks in several villages.

Scientists explain WHY?

Explaining the sudden change, senior lecturer at the Institute of Earth Sciences and the Hebrew University of Jerusalem, Moshe Armon said, as NASA quoted, “While some degree of rainfall in this region happens every summer, what’s unique this year is the involvement of an extratropical cyclone.”

He added that cyclone was formed over the Atlantic Ocean and extended far southward, pulling moisture from equatorial Africa into the northern Sahara.

According to the preliminary satellite analysis, more than 200 millimeters of rainfall fell in the affected areas, which is roughly equivalent to what the region receives in a year.

The rainfall accumulation estimates are based on NASA’s IMERG (Integrated Multi-Satellite Retrievals for GPM) data due to ground-based rain gauges and radar stations being scarce.

“What’s also fascinating is that normally dry lakes in the Sahara are filling due to this event,” Armon added.

On closer inspection, several of these lakes are visible in the image as dark blue areas, including one in Morocco’s Iriqui National Park and Sebkha el Melah, a salt flat in central Algeria.

When Prof Armon and his colleagues analysed two decades (2000–2021) of IMERG data to better understand the frequency of heavy precipitation events, they identified only six prior occurrences that led to the lake filling.

The researchers identified more than 38,000 heavy precipitation events over the Sahara and found that roughly 30 per cent of those occurred during the summer.