Identifying compound extremes in the Amazon rainforest: dry-hot and dry-wet events

The Amazon rainforest is one of the most ecologically diverse and important ecosystems on Earth and plays a fundamental role in regulating the global climate. Extreme weather events, such as droughts, heatwaves, and floods, can lead to various consequences such as increased soil erosion, altered water availability, and changes in vegetation dynamics, which can affect the Amazon forest's carbon balance, biodiversity, and overall ecosystem functioning. Moreover, global-scale studies employing Coupled Model Intercomparison Project Phase 6 (CMIP6) future climate scenarios project an increase in extreme events over South America, further emphasizing the vulnerability of the Amazon forest ecosystem. 

Previous studies have examined heatwaves, droughts, and extreme precipitation events within the Amazon forest as singular extreme events. However, few studies have considered these weather extremes simultaneously as compound or concurrent extreme events. These compound events can have a more significant impact than individual extreme events alone; recent research has shown that the occurrence of combined drought and heatwave can increase the probability of vegetation decline compared to the individual effects of these events. Furthermore, existing research has primarily focused on hot-dry compound events, leaving a knowledge gap regarding the occurrence of combined hot and wet extremes.

In this context, the main research question addressed in this study is: What is the climatology of compound hot-dry and hot-wet extreme events in the Amazon region? To answer this question, our analysis involves identifying compound events of heatwaves and dry spells (hot-dry) and heatwaves and extreme precipitation (hot-wet) events that have occurred in the Amazon region over the last few decades. For this, we utilize data on maximum temperature and precipitation from rain gauges and weather stations, as well as from gridded datasets. The intensity and frequency of the compound events will be discussed, as well as the main atmospheric drivers.