Assessing the relative importance of dry-season incoming solar radiation and water storage dynamics during the 2005, 2010 and 2015 southern Amazon droughts: not all droughts are created equal

Shuang Liu; Tim R McVicar; Xue Wu; Xin Cao; Yi Liu

doi:10.1088/1748-9326/ad281e

Environmental Research Letters (Jan 2024)

Assessing the relative importance of dry-season incoming solar radiation and water storage dynamics during the 2005, 2010 and 2015 southern Amazon droughts: not all droughts are created equal

Shuang Liu,
Tim R McVicar,
Xue Wu,
Xin Cao,
Yi Liu

Affiliations

Shuang Liu: ORCiD; Water Research Centre, University of New South Wales , Sydney, Australia; ARC ITTC Data Analytics for Resources and Environments, University of New South Wales , Sydney, Australia
Tim R McVicar: ORCiD; CSIRO Environment , Canberra, ACT, Australia; Australian Research Council Centre of Excellence for Climate Extremes , Canberra, ACT, Australia
Xue Wu: School of Computer Science and Engineering, University of New South Wales , Sydney, Australia
Xin Cao: ORCiD; School of Computer Science and Engineering, University of New South Wales , Sydney, Australia
Yi Liu: ORCiD; School of Civil and Environmental Engineering, University of New South Wales , Sydney, Australia

DOI: https://doi.org/10.1088/1748-9326/ad281e
Journal volume & issue: Vol. 19, no. 3
p. 034027

Abstract

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Three severe droughts impacted the Amazon in 2005, 2010, and 2015, leading to widespread above-average land surface temperature (LST) (i.e. positive thermal anomalies) over the southern Amazon in the dry season (Aug–Sep) of these years. Below-average dry-season incoming solar radiation (SW↓) and terrestrial water storage anomaly (TWSA) were simultaneously observed in 2005 and 2010, whereas the opposite was observed in 2015. We found that anomalies in precipitation (P), SW↓, and TWSA combined can well explain dry-season thermal anomalies during these droughts (average R ^2 –0.51). We investigated the causes for opposing anomalies in dry-season SW↓ and TWSA, and found different hydro-climatological conditions preceding the drought-year dry seasons. In 2005 and 2010, P was considerably below average during the wet-to-dry transition season (May–July), causing below-average TWSA in the dry season that was favorable for fires. Increased atmospheric aerosols resulting from fires reduced solar radiation reaching the ground. In 2015, although below-average dry-season P was observed, it was above the average during the wet-to-dry transition season, leading to reduced fires and aerosols, and increased dry-season SW↓. To further examine the impact of opposite hydro-climatological processes on the drought severity, we compared dry-season LST during droughts with the maximum LST during non-drought years (i.e. LST _max ) for all grid cells, and a similar analysis was conducted for TWSA with the minimum TWSA (i.e. TWSA _min ). Accordingly, the regions that suffered from concurrent thermal and water stress (i.e. LST > LST _max and TWSA < TWSA _min ) were identified. These regions are mainly observed over the southeast in 2005 and southern Amazon in 2010. In 2015, large-scale dry-season thermal stress was found over central and southeast Amazon with little water stress. This study underlines the complex interactions of different hydro-climatological components and the importance of understanding the evolution of droughts to better predict their possible impacts on the Amazon rainforest.

Published in Environmental Research Letters

ISSN: 1748-9326 (Online)
Publisher: IOP Publishing
Country of publisher: United Kingdom
LCC subjects: Technology: Environmental technology. Sanitary engineering; Geography. Anthropology. Recreation: Environmental sciences; Science: Physics
Website: https://iopscience.iop.org/journal/1748-9326

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