The finding comes from a study reported by scientists from Brazil, China, Australia and Germany in the journal Geophysical Research Letters. The team used a new methodology that focuses on low rainfall and severe drought
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Sea surface temperatures in the North Atlantic may be a predictor of up to three months of extreme climate events associated with reduced rainfall and severe drought in the Northeast region of Brazil. This is one of the main findings of the study by researchers in Brazil, China, Australia and Germany, according to a paper. published In Geophysical research letter.
Using a new methodology based on the concept of precipitation deficits, the study has shown that in recent years, the influence of the North Atlantic Ocean has become more persistent than the influence of the tropical Pacific Ocean, is still considered to be one of the main factors causing drought intensity. by Northeast. At the same time, atmospheric connections between the Pacific and North Atlantic have become more frequent, suggesting that interactions between tropical ocean basins have further reinforced the droughts occurring in the region. in recent decades.
“The study was driven by a severe drought that lasted from 2012 to 2015. This long period got us thinking, from a meteorological point of view, about how tropical ocean temperatures affect climate. Queen. The current difference is the innovative methodology that explores the contrast between the Pacific and Atlantic oceans, and the drought pattern in Northeast Brazil. The findings can be used as a tool to manage weather forecasts in advance of these potential events,” said Lincoln Muniz Alves, a scientist at Brazil’s National Institute for Space Research (INPE) and co-author the author of the article, said Agência FAPESP.
Research supported by FAPESP through a Thematic project connect with National Institute of Science and Technology on Climate Change (INCT-CC). The Principal Investigator of the Thematic Project is Elbert Einstein Nehrer Macaua professor at the Federal University of São Paulo (UNIFESP).
The 2012-15 drought in parts of the Northeast, which was classified as semi-arid, was so severe that it destroyed crops and left cities and villages short of water. Other studies have identified changes in atmospheric circulation as the main cause, suggesting that a positive role is due to the warmer-than-normal Atlantic surface temperature and by El Niño, a phenomenon climate phenomenon associated with unusually warm temperatures in the Pacific Ocean.
This El Niño is considered one of the strongest (after 1982-83 and 1997-98) and caused damage in different parts of the world. In Brazil, negative effects include severe drought in the Northeast and Amazon, a longer-than-usual dry season in the North and parts of central Brazil (northern regions of the states of Minas Gerais and Goiás as well as the Federal District), and flooding in the South.
“This type of El Niño, called ‘classic’ because of the unusual warming occurring in the same specific area of the Pacific Ocean, has varied in both location and magnitude. In parallel, we have seen unusual warming in the tropics of the Atlantic in recent decades. Based on our multifaceted analysis, the paper provides ample evidence for forecasters to watch for signs coming in from the tropics several months in advance. The influence of the Pacific is undeniable, but the Atlantic is much more than that,” said Alves.
As explained by the authors, the study uses methods such as non-linear phase matching and general event synchrony to understand the underlying cause-and-effect mechanisms of controlled climate phenomena. check. Thus, the relationships between sea surface temperature variation and the standard precipitation index are interpreted as direct interactions, while the inter-ocean relationships are interpreted as indirect effects on the amount of precipitation. rain.
The researchers used precipitation data from the Climate Prediction Center (CPC), a branch of the National Oceanic & Atmospheric Administration’s (NOAA-NWS) National Weather Service. They selected four regions: Northeast Brazil, the center of drought for decades; an area known as Niño 3, where there is intense El Niño Southern Oscillation (ENSO) activity; and the North and South Atlantic, regions that have been analyzed in previous studies.
To verify consistency, they compared the results with Niño 4, an area that includes the central equatorial Pacific and parts of the South Atlantic. For each domain, they calculated the spatial mean of the variable of interest and the daily anomaly relative to the baseline for the period 1981-2010. The rainy season is defined as from January to April and the dry season is from May to August.
They concluded that the North Atlantic was the main influence on rainfall deficits and the occurrence of droughts during the period analyzed. Rain frequency and sea surface temperature changes after El Niño and La Niña events are very strong, increasing the possibility of phase coherence.
“A normal or linear model like the one seen three decades ago no longer exists,” says Alves. “Several other studies have corroborated our results. Our methodology shows that no linear model exists as a basis for forecasting and conventional approaches should be abandoned. We emphasize the importance of looking at other oceans rather than just focusing on the Pacific.”
The paper also concludes that other factors such as changes in land use can lead to changes in the hydrological cycle, as demonstrated by modeling studies, especially with regard to watersheds. Amazon River. For this reason, the scientists suggest that further studies using the method they have developed should investigate whether land-use changes alter climate features and interactions such as how.
“When we discuss climate change, we are also talking about socioeconomic impacts and effects on biodiversity. Meteorological centers can use this model to work in prevention as a contribution to public policy and decision-making about mitigating extreme events,” said Alves.
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Geophysical research letter
Phase coupling between surrounding oceans enhances rainfall deficits in Northeast Brazil
ARTICLE PUBLICATION DATE
April 22, 2022