Recent increasing frequency of compound summer drought and heatwaves in Southeast Brazil

Abstract

An increase in the frequency of extremely hot and dry events has been experienced over the past few decades in South America, and particularly in Brazil. Regional climate change projections indicate a future aggravation of this trend. However, a comprehensive characterization of drought and heatwave compound events, as well as of the main land–atmosphere mechanisms involved, is still lacking for most of South America. This study aims to fill this gap, assessing for the first time the historical evolution of compound summer drought and heatwave events for the heavily populated region of Southeast Brazil and for the period of 1980–2018. The main goal is to undertake a detailed analysis of the surface and synoptic conditions, as well as of the land–atmosphere coupling processes that led to the occurrence of individual and compound dry and hot extremes. Our results confirm that the São Paulo, Rio de Janeiro and Minas Gerais states have recorded pronounced and statistically significant increases in the number of compound summer drought and heatwave episodes. In particular, the last decade was characterized by two austral summer seasons (2013/14 and 2014/15) with outstanding concurrent drought and heatwave conditions stemmed by severe precipitation deficits and a higher-than-average occurrence of blocking patterns. As result of these land and atmosphere conditions, a high coupling (water-limited) regime was imposed, promoting the re-amplification of hot spells that resulted in mega heatwave episodes. Our findings reveal a substantial contribution of persistent dry conditions to heatwave episodes, highlighting the vulnerability of the region to climate change.

Heat waves in São Paulo State, Brazil: Intensity, duration, spatial scope, and atmospheric characteristics

“…This result corroborates that reported by previous studies: the association of a quasi‐stationary anticyclonic circulation with HWs is referred to as a blocking event (Alves et al, 2016; Geirinhas et al, 2021). This atmospheric pattern is characterized by a hot and dry air mass associated with subsidence air that inhibits the formation of nebulosity capable of producing rain.…”

Heat waves in São Paulo State, Brazil: Intensity, duration, spatial scope, and atmospheric characteristics

“…This result corroborates that reported by previous studies: the association of a quasi‐stationary anticyclonic circulation with HWs is referred to as a blocking event (Alves et al, 2016; Geirinhas et al, 2021). This atmospheric pattern is characterized by a hot and dry air mass associated with subsidence air that inhibits the formation of nebulosity capable of producing rain.…”

Increasing Risks of Future Compound Climate Extremes With Warming Over Global Land Masses

“…For instance, in NSA and WCE (Figures 4d and 4e), BDHI exhibited a declining trend in future, indicating that the severity of compound dry–hot events would tend to intensify. This is generally in line with the observations of compound dry–hot events frequently attacking these regions (Geirinhas et al., 2021; Hao et al., 2018b; Manning et al., 2019; Pfleiderer et al., 2019; Zscheischler & Fischer, 2020). As for the other selected hot spots, BDHI would be mainly maintaining a relatively stable state in future.…”

Spatiotemporal analysis of compound droughts and heat waves in the Horn of Africa

“…This consistency in outcomes across various studies emphasizes the pressing nature of the problem and its relevance to the distinct challenges experienced by this region (Abera et al, 2020; Dosio et al, 2018; Omondi et al, 2014). Furthermore, our investigation aligns with the broader global trend of increasing temperatures and escalating frequency of extreme heat episodes due to climate conditions alterations (Geirinhas et al, 2021; Sun et al, 2019). This regional consistency mirrors the worldwide pattern of more frequent and severe episodes of extreme heat observed in assorted regions across the globe (Ahsan et al, 2022; Libonati et al, 2022).…”

Heat waves in São Paulo State, Brazil: Intensity, duration, spatial scope, and atmospheric characteristics

“…This result corroborates that reported by previous studies: the association of a quasi‐stationary anticyclonic circulation with HWs is referred to as a blocking event (Alves et al, 2016; Geirinhas et al, 2021). This atmospheric pattern is characterized by a hot and dry air mass associated with subsidence air that inhibits the formation of nebulosity capable of producing rain.…”

Increasing Risks of Future Compound Climate Extremes With Warming Over Global Land Masses

“…For instance, in NSA and WCE (Figures 4d and 4e), BDHI exhibited a declining trend in future, indicating that the severity of compound dry–hot events would tend to intensify. This is generally in line with the observations of compound dry–hot events frequently attacking these regions (Geirinhas et al., 2021; Hao et al., 2018b; Manning et al., 2019; Pfleiderer et al., 2019; Zscheischler & Fischer, 2020). As for the other selected hot spots, BDHI would be mainly maintaining a relatively stable state in future.…”

Spatiotemporal analysis of compound droughts and heat waves in the Horn of Africa

“…This consistency in outcomes across various studies emphasizes the pressing nature of the problem and its relevance to the distinct challenges experienced by this region (Abera et al, 2020; Dosio et al, 2018; Omondi et al, 2014). Furthermore, our investigation aligns with the broader global trend of increasing temperatures and escalating frequency of extreme heat episodes due to climate conditions alterations (Geirinhas et al, 2021; Sun et al, 2019). This regional consistency mirrors the worldwide pattern of more frequent and severe episodes of extreme heat observed in assorted regions across the globe (Ahsan et al, 2022; Libonati et al, 2022).…”

Heat waves in São Paulo State, Brazil: Intensity, duration, spatial scope, and atmospheric characteristics

“…This result corroborates that reported by previous studies: the association of a quasi‐stationary anticyclonic circulation with HWs is referred to as a blocking event (Alves et al, 2016; Geirinhas et al, 2021). This atmospheric pattern is characterized by a hot and dry air mass associated with subsidence air that inhibits the formation of nebulosity capable of producing rain.…”

Increasing Risks of Future Compound Climate Extremes With Warming Over Global Land Masses

“…For instance, in NSA and WCE (Figures 4d and 4e), BDHI exhibited a declining trend in future, indicating that the severity of compound dry–hot events would tend to intensify. This is generally in line with the observations of compound dry–hot events frequently attacking these regions (Geirinhas et al., 2021; Hao et al., 2018b; Manning et al., 2019; Pfleiderer et al., 2019; Zscheischler & Fischer, 2020). As for the other selected hot spots, BDHI would be mainly maintaining a relatively stable state in future.…”

Spatiotemporal analysis of compound droughts and heat waves in the Horn of Africa

“…This consistency in outcomes across various studies emphasizes the pressing nature of the problem and its relevance to the distinct challenges experienced by this region (Abera et al, 2020; Dosio et al, 2018; Omondi et al, 2014). Furthermore, our investigation aligns with the broader global trend of increasing temperatures and escalating frequency of extreme heat episodes due to climate conditions alterations (Geirinhas et al, 2021; Sun et al, 2019). This regional consistency mirrors the worldwide pattern of more frequent and severe episodes of extreme heat observed in assorted regions across the globe (Ahsan et al, 2022; Libonati et al, 2022).…”