Figure 1: Illustration of the formation of the atmospheric river over South America. (Source: http://riosvoadores.com.br/wp-content/uploads/sites/5/2013/05/diagrama.png , accessed in 08/06/2021 at 14:39h)
Atmospheric river are flowing columns of long, narrow “ribbons” of condensed air which carry large amounts of water vapor. This phenomenon is a fundamental, determinant of the balance of the ecosystem and biodiversity in various regions of the world.
In Brazil, without the existence of atmospheric rivers, the Center-South region, as well as other continental regions located between the same latitudes, likely would be deserts. Due to its different climate from other regions, the center-south of Brazil has been termed as the “lucky quadrilateral”; the main reason for an atmospheric river existing in this area is the presence of the Amazon forest.
The Amazon works as a water pump, which pulls the moisture evaporated by the Atlantic Ocean into the continent, carried by the trade winds. This moisture is converted into rain on the forest, which in turn transpires and returns the water to the atmosphere in the form of vapor. The large mass of moisture formed is transported westwards by the winds, with part falling earlier as rain and the remainder continuing until it collides with the Andes Mountains, where the headwaters of Amazon rivers are formed and water vapor is diverted towards south-central region of Brazil, regulating rainfall in the region. Neighboring countries such as Paraguay and Bolivia also have their rainfall regimes regulated by aerial rivers. Figure 1 illustrates the formation of the atmospheric river over Brazil.
With the deforestation of the Amazon area, the atmospheric rivers are suffering a reduction in their moisture load, which results in a reduction in rainfall in the Midwest regions, directly impacting the country’s agriculture, livestock and economy.
Atmospheric rivers also occur in other regions of the globe. According to the National Oceanic and Atmospheric Administration (NOAA), although they come in many shapes and sizes, those that contain the greatest amounts of water vapor and the strongest winds can create extreme rainfall and flooding, often hitting watersheds vulnerable to flooding. These events can disrupt travel, induce landslides and cause catastrophic damage to life and property. One example is the “Pineapple Express”, an atmospheric river that is able to bring moisture from the tropics to the west coast of the United States. (Figure 2). Although the strongest atmospheric rivers often cause damaging effects, most are weak systems that often provide rain or snow which is critical to water supply.
Understanding and protecting the environment is extremely important for the survival of humanity, because in nature something which superficially appears to be only “local” actually can affect regions that are thousands of kilometers away. Changing nature may produce consequences that change your own destiny!
Atlanta, August 17, 2021
By L. Ferreira and L.B.M. Pires
Source:
https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2020GL091076
https://www.noaa.gov/stories/what-are-atmospheric-rivers
https://www.fenatema.org.br/noticia/desmatamento-na-amazonia-vai-provocar-grande-seca-no-brasil/5585