the Creative Commons Attribution 4.0 License.
the Creative Commons Attribution 4.0 License.
| 23 Apr 2025
Physical Drivers of the November 2023 Heatwave in Rio de Janeiro
Abstract. As extreme heat has not historically been a major hazard for the city of Rio de Janeiro, the November 2023 Heatwave magnitude and timing were staggering. Here we conduct a case study of reanalysis data and high-resolution projections to explore the event drivers and characterize the evolving extreme heat risk in the city of Rio de Janeiro. We find that the heatwave was associated with atmospheric blocking, potentially linked to the 2023–24 El Niño event. Soil moisture declines increased surface sensible heat flux, and elevated sea surface temperatures reduced coastal cooling. The heatwave was preceded by weeks of suppressed precipitation and terminated by the onset of rain. We also find a significant historical increase in the frequency of high heat days throughout Brazil and a lengthening of the heat season in the city of Rio de Janeiro. The frequency of the city’s austral spring heat extremes is expected to increase further in the future, highly dependent upon our future emissions pathway. These results emphasize the rapidly emerging risk for extreme heat in the city of Rio de Janeiro.
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Notice on discussion status
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
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Preprint
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The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
Journal article(s) based on this preprint
Interactive discussion
Status: closed
- RC1: 'Comment on egusphere-2025-1427', Anonymous Referee #1, 15 May 2025
- RC2: 'Comment on egusphere-2025-1427', Anonymous Referee #2, 04 Jun 2025
- AC1: 'Comment on egusphere-2025-1427', Catherine Ivanovich, 24 Jul 2025
Interactive discussion
Status: closed
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RC1: 'Comment on egusphere-2025-1427', Anonymous Referee #1, 15 May 2025
Summary:
Using station-based and reanalysis data, this authors present a valuable analysis of the unprecedented November 2023 Rio de Janeiro heatwave, highlighting the driving effect of atmospheric blocking and its linkage to the El Nino event. They also discuss the role of soil moisture deficits associated with the heat extreme event. Finally, they extend the analysis to future projection and find that the frequency of heat extremes is expected to increase in the future. The paper is well-written and present clear results. However, the physical driving mechanism analyses could be further strengthened by quantifying the relative roles of blocking and soil moisture decline in driving the heat extremes. Moreover, the robustness of the linkage between the atmospheric blocking and ENSO needs to be further clarified. I thus recommend a major revision by addressing the following comments.
Specific comments:
1, One major goal of this study is to figure out the physical drivers of the November 2023 heatwaves. I would like to recommend the authors to perform a thermal budget analysis, which would be helpful to understand the relative contributions of atmospheric circulation and diabatic heating that is mainly influenced by the surface heat fluxes and soil moisture.
2, In the abstract, the authors claim the atmospheric blocking is affected by the El Nino, but they did not provide sufficient evidence for this in the historical analysis. Particularly, they only show the historical correlation between Nino 3.4 index and number of days in heat extreme. I would like to suggest to perform the circulation composite in the spring of El Nino years.
Citation: https://doi.org/10.5194/egusphere-2025-1427-RC1 - RC2: 'Comment on egusphere-2025-1427', Anonymous Referee #2, 04 Jun 2025
- AC1: 'Comment on egusphere-2025-1427', Catherine Ivanovich, 24 Jul 2025
Peer review completion
Journal article(s) based on this preprint
Data sets
HadISD v3 R. J. H. Dunn https://www.metoffice.gov.uk/hadobs/hadisd/
ERA5 hourly data on single levels from 1940 to present H. Hershbach et al. https://cds.climate.copernicus.eu/datasets/reanalysis-era5-single-levels?tab=overview
ERA5 hourly data on pressure levels from 1940 to present H. Hershbach et al. https://cds.climate.copernicus.eu/datasets/reanalysis-era5-pressure-levels?tab=overview
NOAA 1/4° Daily Optimum Interpolation Sea Surface Temperature Dataset (OISST) B. Huang et al. https://www.ncei.noaa.gov/products/optimum-interpolation-sst
NASA Global Daily Downscaled Projections (NEXGDDP) B. Thrasher et al. https://www.nccs.nasa.gov/services/data-collections/land-based-products/nex-gddp-cmip6
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- 1
Catherine C. Ivanovich
Adam H. Sobel
Radley M. Horton
Ana M. B. Nunes
Rosmeri Porfírio Rocha
Suzana J. Camargo
The requested preprint has a corresponding peer-reviewed final revised paper. You are encouraged to refer to the final revised version.
Summary:
Using station-based and reanalysis data, this authors present a valuable analysis of the unprecedented November 2023 Rio de Janeiro heatwave, highlighting the driving effect of atmospheric blocking and its linkage to the El Nino event. They also discuss the role of soil moisture deficits associated with the heat extreme event. Finally, they extend the analysis to future projection and find that the frequency of heat extremes is expected to increase in the future. The paper is well-written and present clear results. However, the physical driving mechanism analyses could be further strengthened by quantifying the relative roles of blocking and soil moisture decline in driving the heat extremes. Moreover, the robustness of the linkage between the atmospheric blocking and ENSO needs to be further clarified. I thus recommend a major revision by addressing the following comments.
Specific comments:
1, One major goal of this study is to figure out the physical drivers of the November 2023 heatwaves. I would like to recommend the authors to perform a thermal budget analysis, which would be helpful to understand the relative contributions of atmospheric circulation and diabatic heating that is mainly influenced by the surface heat fluxes and soil moisture.
2, In the abstract, the authors claim the atmospheric blocking is affected by the El Nino, but they did not provide sufficient evidence for this in the historical analysis. Particularly, they only show the historical correlation between Nino 3.4 index and number of days in heat extreme. I would like to suggest to perform the circulation composite in the spring of El Nino years.