Forest Mortality and Extreme Storms in Amazonia

This study identifies 38 cases of Amazonia windthrows to explore the relationship between windthrows and the mesoscale convective systems producing them.

The workflow of correlating a windthrow event on the land surface to its associated convective storm in the atmosphere using remote sensing images from both land and meteorological satellites.

[Reprinted under a Creative Commons Attribution 4.0 International License (CC BY 4.0) from Feng, Y., et al. "Case Studies of Forest Windthrows and Mesoscale Convective Systems in Amazonia." Geophysical Research Letters 50 (12), e2023GL104395 (2023). DOI:10.1029/2023GL104395.]

The Science

Fan-shaped dead forest patches were found over the entire Amazonia that cover over 37 hectares, affecting the role Amazon forests play in the global carbon cycle. Scientists found frequent storms happen in these dead forest patches, but how does the process happen? This study explores the three characteristics of storms (passing over time, cloud top temperature, and associated precipitation) to identify their relationship with the size of the dead forests. Results show that long-lived storms with thick and tall clouds result in bigger sizes of dead forest patches. Moreover, forests in western Amazonia are more vulnerable to storms than forests in other parts.

The Impact

This research explores how extreme storms impact tree loss in tropical forests, especially in the Amazon. These storms, responsible for 50–90% of annual rainfall in the tropics, often result in toppling trees, which disrupts the forest’s ability to store carbon, a crucial ability to fight climate change. These phenomena have been studied separately in the past, but this study connects them. By analyzing satellite data, researchers have uncovered relationships between the characteristics of extreme storms and tree loss sizes. This understanding can improve climate models and provide more accurate predictions about the changing environment.

Summary

This study delves into the relationship between large-scale storm systems known as mesoscale convective systems (MCSs) and the phenomenon of ‘windthrow’—when storms uproot trees—in the Amazon rainforest. Researchers examined 38 pairs of windthrow and their associated MCS events to identify the specific storm characteristics influencing the extent of windthrow. MCSs with a longer storm duration tended to result in more extensive windthrow. A positive correlation was found between the storm’s duration and the area of forest affected.

The depth of convection clouds within the storm also played a role. Deep convection caused larger windthrow across the entire Amazon. In contrast, shallow convection led to medium-sized windthrows in western Amazonia and smaller ones in central Amazonia. Interestingly, rainfall wasn’t uniformly distributed among forest disturbances of the same size, suggesting the need for more precise precipitation data to establish a clearer relationship with windthrow sizes.

This study offers detailed case studies on windthrows and corresponding MCS features. It reduces the uncertainty of previous research due to data mismatches between MCSs and windthrows, offering fresh insights into how land and atmosphere interact. These findings are important for refining climate models and, ultimately, understanding climate change impacts on the ecosystem.

Principal Investigator

Yanlei Feng
University of California–Berkeley
[email protected]

Program Manager

Brian Benscoter
U.S. Department of Energy, Biological and Environmental Research (SC-33)
Environmental System Science
[email protected]

Funding

This research was supported as part of the Next-Generation Ecosystem Experiments Tropics, funded by the Biological and Environmental Research (BER) program within the U.S. Department of Energy’s Office of Science under contract number DE-AC02-05CH11231. The World Climate Research Programme through its Working Group on Coupled Modelling coordinated and promoted Coupled Model Intercomparison Project Phase 6 (CMIP6). Support was also received from climate modeling groups that produced and made available their model output, the Earth System Grid Federation (ESGF) that archived the data and provided access, and multiple funding agencies that support CMIP6 and ESGF.

References

Feng, Y., et al. "Case Studies of Forest Windthrows and Mesoscale Convective Systems in Amazonia." Geophysical Research Letters 50 (12), e2023GL104395  (2023). https://doi.org/10.1029/2023GL104395.