This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Research Article
Victor Azevedo Godoi
OceanPact Geo Ltd
Corresponding Author
ORCiD: https://orcid.org/0000-0001-7951-3017
License:
This work is licensed under a CC BY 4.0 License. Read Full License
El Niño is generally associated with below-average rainfall in northeastern Brazil (NEB). In 2019, however, the opposite rainfall pattern was observed during an El Niño episode. Here, we explore the mechanisms that overwhelmed typical El Niño-related conditions and resulted in above-average rainfall in NEB. We focus on the austral autumn, when El Niño is most related to rainfall anomalies in the region. The analysis of rainfall data from weather stations and the Global Precipitation Climatology Project, upper- and lower-level circulation reanalysis data, sea surface temperature data, outgoing longwave radiation data, and modelled data allowed us to identify that the autumn 2019 heavy rainfall in NEB was likely associated with three combined factors; these are: (1) the weak intensity of the 2019 El Niño; (2) local and remote diabatic heating anomalies, especially over the western South Pacific and tropical South Atlantic, which resulted in anticyclonic and cyclonic circulations in the upper and lower troposphere, respectively, over the tropical South Atlantic; and (3) sub-seasonal atmospheric convection anomalies over the western South Pacific, which reinforced the low-frequency convection signal over that region. This latter factor suggests the influence of the Madden–Julian Oscillation on rainfall in NEB during the first ten days of March. We discuss these mechanisms in detail and provide evidence for their associations with the anomalously heavy rainfall in NEB. Our results may assist in the planning of several crucial activities, such as water resources management and agriculture.
Keywords
Rainfall, northeastern Brazil, El Niño, anomalous heat sources, Madden–Julian Oscillation (MJO), linear baroclinic model
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This is a preprint, a preliminary version of a manuscript that has not completed peer review at a journal. Research Square does not conduct peer review prior to posting preprints. The posting of a preprint on this server should not be interpreted as an endorsement of its validity or suitability for dissemination as established information or for guiding clinical practice.
Research Article
Victor Azevedo Godoi
OceanPact Geo Ltd
Corresponding Author
ORCiD: https://orcid.org/0000-0001-7951-3017
Badges
Prescreen
This manuscript passed our Prescreen assessment
Complete author information
Appropriate declaration statements
Potential risks to human health
Prescreen
History
CURRENT STATUS: Posted
Version 1
Posted 04 Aug, 2021
No community comments so far
Metrics
Comments: 0
PDF Downloads: ...
HTML Views: ...
Subject Areas
Climatology
License:
This work is licensed under a CC BY 4.0 License. Read Full License
El Niño is generally associated with below-average rainfall in northeastern Brazil (NEB). In 2019, however, the opposite rainfall pattern was observed during an El Niño episode. Here, we explore the mechanisms that overwhelmed typical El Niño-related conditions and resulted in above-average rainfall in NEB. We focus on the austral autumn, when El Niño is most related to rainfall anomalies in the region. The analysis of rainfall data from weather stations and the Global Precipitation Climatology Project, upper- and lower-level circulation reanalysis data, sea surface temperature data, outgoing longwave radiation data, and modelled data allowed us to identify that the autumn 2019 heavy rainfall in NEB was likely associated with three combined factors; these are: (1) the weak intensity of the 2019 El Niño; (2) local and remote diabatic heating anomalies, especially over the western South Pacific and tropical South Atlantic, which resulted in anticyclonic and cyclonic circulations in the upper and lower troposphere, respectively, over the tropical South Atlantic; and (3) sub-seasonal atmospheric convection anomalies over the western South Pacific, which reinforced the low-frequency convection signal over that region. This latter factor suggests the influence of the Madden–Julian Oscillation on rainfall in NEB during the first ten days of March. We discuss these mechanisms in detail and provide evidence for their associations with the anomalously heavy rainfall in NEB. Our results may assist in the planning of several crucial activities, such as water resources management and agriculture.
Figure 1
Figure 2
Figure 3
Figure 4
Figure 5
Figure 6
Figure 7
Figure 8
Figure 9
Figure 10
Figure 11
This preprint is available for download as a PDF.
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