Published: Sunday, May 19, 2020
Editor’s Notes
This article has been reviewed by Science X.
Editorial process
Policies.
Editors have highlighted
The content must have the following attributes to ensure its credibility:
fact-checked
Trusted source
Written by a researcher
Proofread
Marcia Zilli and Caio Coelho, The Conversation
Credit: Unsplash/CC0 public domain
It’s not what you think. A powerful river flows out of the Amazon rain forest. A “flying stream” transports moisture from Amazonian tree canopy southwards, along the Andes Mountains, towards Rio Grande do Sul. This is the southernmost Brazilian state.
Nearly the entire state, an area bigger than the UK, is currently experiencing unprecedented flooding. The flying river acted as a firehose and triggered five months’ worth of rain in two weeks. This was further exacerbated by a jetstream that was located at the wrong altitude above the area. Climate change projections indicate that this situation is likely to worsen as temperatures rise.
Rio Grande do Sul has been in the news since May 1. The Guaiba River in Porto Alegre is five meters higher than normal, breaking the 1941 record. The death toll continues to rise, and 108 people are still missing. Floods in 446 out of 497 municipalities have affected or displaced over 600,000 people.
In many municipalities, water and energy systems have collapsed leaving thousands of homes without power or water. The state’s major roads, airport and schools are closed. Schools have suspended classes.
A heat wave has caused temperatures to reach record highs in Sao Paulo and Minas Gerais, while the south of the country is flooded. This is comparable to the entire northern France being under water while Barcelona swelters with 40degC temperatures.
It is not the first disaster to hit the southernmost region of Brazil. Floods from September to November 2023 and major floods in 1997 or 1983 were caused by similar weather systems. These featured moisture from the Amazon at the surface, and a jetstream crossing the Andes above.
These floods are more likely to occur when a combination of factors is present. These weather systems are associated with warm ocean temperatures (which is still the case even though El Nino has started to fade) and abnormally warm temperatures in the tropical Atlantic, which adds more moisture to air that’s brought south by the flying rivers.
What’s to come
Does this event foretell what is to come in the southern Brazil? The atmosphere can hold more water as it warms up, so there’s a chance of heavy rains and massive clouds. It’s like buying a sponge that can hold more, but it will leak more water when squeezed.
We are already seeing this. This time, compared with the 1941 floods, the excessive rain was concentrated over a shorter period of time, which meant that the water rose faster. Future climate projections indicate that a warming atmosphere will result in a greater intensity of flying rivers, from the Amazon to south Brazil and the adjacent regions.
We have analysed results from the most advanced climate models, which are capable of simulating storms in South America to a fine detail. These models can simulate storms as small as a few kilometers. They indicate that extreme rain events like those occurring now will become more common in the future. Previous climate models may have underestimated the risks.
These simulations are used in South America and southern Brazil to assess these risks. Early results indicate that short, intense rains will be more common in South America and Brazil, regardless of whether the climate systems are unique to certain regions.
This article was republished by The Conversation, under a Creative Commons License. The original article can be read.
Source: Phys.org