In February 2022, the Brazilian city of Petrópolis suffered a storm of heavy rains. The city, located 68 kilometers north of Rio de Janeiro, suffered the worst rains in the last 90 years. The storm left at least 117 dead and the threat of further heavy rains. However, behind this tragedy lies a natural phenomenon. It is the massive aerial flows of water in the form of steam that are transported from the tropical Atlantic Ocean. As they pass through the Amazon, they feed on the humidity of the environment. They are popularly known as flying rivers.
what are flying rivers?
Rivers of atmospheric moisture move swiftly through the Amazon. They reach as far as the Andes mountain range on their course. Although on their way they often cause rains 3000 kilometers away. Both in southern Brazil and in Paraguay, Uruguay and northern Argentina.
These rivers are transported in atmospheric corridors at a height of about 2 kilometers. The problem is that they can carry as much water as the Amazon River. That is why they are called flying rivers. However, this atmospheric phenomenon is vital for regional economies. They are essential for agriculture and the lives of many people in Latin America. But they can also become as devastating as what happened in Petrópolis.
In this imperial city of Brazil, rains caused landslides. More than 200 landslides swept away vast areas of the city causing death in their wake. Rescue teams are working hard to search for survivors among the mud and rocks.
Characteristics of the flying rivers
Flying rivers start in the Atlantic, a warm ocean. Therefore, the heat causes it to evaporate a lot of water, which, passing through the humidity of the Amazon, loads up with more water. The trade winds are in charge of transporting all that humid load to the lower levels of the atmosphere.
As in the currents of a river, there are calm zones and others of greater intensity. The same happens with the flying rivers, when they meet the Andes Mountains they acquire greater velocity. When they collide with the mountain range, the humid load turns towards southeastern Brazil and reaches the Río de la Plata. It is the very relief of South America that does not allow this moisture to escape, forcing the flying rivers to descend.
In addition to the formation of moisture by evaporation in the Atlantic, the flying rivers are fed by the trees of the Amazon. A leafy tree, about 20 meters in diameter, can transpire about 1000 liters of water in a single day.
The Amazon consists of 5.5 million square kilometers of tropical forest. It is not hard to imagine the amount of water that is expelled into the atmosphere and supplies the flying rivers. That’s 20 billion tons of water transpiring daily through the trees of the Amazon basin.
The storm that affected Petrópolis was caused by a cold, dry air front that created a barrier for the flying river. Unable to advance the storm, it discharged over the city causing the havoc already described and causing the death of so many people.