Forest-rainfall cascades buffer against drought across the Amazon

Staal, Arie; Tuinenburg, Obbe A.; Bosmans, Joyce; Holmgren, Milena; Nes, Egbert H. van; Scheffer, Marten; Zemp, Delphine Clara; Dekker, Stefan C.

doi:10.1038/s41558-018-0177-y

Cited by 268 publications

(382 citation statements)

References 75 publications

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“…In contrast to precipitation amount, the recycled precipitation fraction changes little between seasons although there is a shift of the maximum from approximately 15°S in the Western Amazon during the dry season to 25°S to 30°S along the Eastern foothills of the Andes to the South of the Amazon during the wet season (Figure b). Spatial patterns and seasonality are similar to previous studies (Staal et al, ; Zemp et al, ), and magnitude of Amazon basin annual mean land‐derived precipitation fraction of 38% is within the range of 10 previous estimates as summarized in Staal et al ().…”

Section: Resultssupporting

confidence: 88%

Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?

Pattnayak

Tindall

Brienen

et al. 2019

Geophysical Research Letters

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Large-scale (>500 km) spatial gradients of precipitation oxygen isotope ratios (δ 18 O p ) hold information about the hydrological cycle. They result from the interplay between rainout and evapotranspiration along air-parcel paths, but these counteracting effects are difficult to disentangle, complicating quantification of the effect of land cover change on δ 18 O p . We show that disentangling can qualitatively be achieved using climate model simulations with a land-derived precipitation tracer for tropical South America. We then either vary land cover as observed since 1870 or replace Amazon forests with bare land to determine the resulting signals. Our results indicate that effects of historically changing land cover on annual mean δ 18 O isotope-ratio gradients are small and unlikely detectable, although there is a noticeable signal during the dry season. Furthermore, the effect of changes in water recycling on Amazon δ 18 O p in paleo-records may have been overestimated and need reinterpretation. Plain Language Summary Deforestation causes reduction in precipitation downwind becausetrees act as pumps of water from soils to the atmosphere. This mechanism is primarily important during the dry season. How strong this effect is currently in the Amazon, given that approximately 20% of the forests have been cut, and how important it may be in the future if more forests are being destroyed is of great interest. One indicator of such changes is the east-west difference in heavy water isotope content of precipitation. While preferential rainout of the heavy isotope along air parcel trajectories enhances this difference, transpiration by forests decreases the difference. This is because forests inject water back into the atmosphere that is more enriched than the overlying water vapor. Records of this difference during the last ice age, in particular, have been interpreted in a previous study as providing information on continental recycling. We apply a land-derived water tagging approach in model simulations to investigate the effect of continental recycling on precipitation isotope content and to estimate this effect for varying land cover. We find that a 20% deforestation has only a small impact on precipitation isotope content. Even for a complete deforestation, in contrast to a previous interpretation, thus, only some of the isotopic signal observed during the ice age can be attributed to changes in continental recycling.

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Section: Resultssupporting

confidence: 88%

Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?

Pattnayak

Tindall

Brienen

et al. 2019

Geophysical Research Letters

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“…2b) decreases everywhere there is vegetation. This decrease is important over the Amazon basin, where precipitation recycling via evapotranspiration is important [e.g., Zemp et al, 2014;Staal et al, 2018] and where decreased moisture flux to the atmosphere will affect the moisture supply available to convection and precipitation. This decrease in transpiration is associated with a diminished latent cooling at the surface ( Fig.…”

Section: Eartharxiv Preprintmentioning

confidence: 99%

“…In addition, precipitation recycling (i.e., the cascade of moisture through precipitation, evapotranspiration, and subsequent precipitation cycles)-especially during the dry season-is a critical source of moisture for the interior rainforest and is estimated to contribute 20-30% of rainfall over the Amazon basin [Brubaker et al, 1993;Eltahir and Bras, 1994;Lee et al, 2005;Van der Ent et al, 2010;Zemp et al, 2014;Staal et al, 2018]. Canopy evapotranspiration is also influential in the dry-to-wet transition season, moistening the lower and middle atmosphere in the months leading up to the monsoon and priming the troposphere for deep convection [Wright et al, 2017].…”

Section: Introductionmentioning

confidence: 99%

Why does Amazon precipitation decrease when tropical forests respond to increasing CO2?

Langenbrunner¹,

Pritchard²,

Kooperman³

et al. 2018

Preprint

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Key Points:• Increasing CO 2 over the Amazon causes a drier, warmer, and expanded boundary layer and reduces basin-wide rainfall within the first day • On synoptic timescales, enhanced lower free troposphere moisture is advected westward by the low-level jet, increasing Andean rainfall • A wetter Andes, dryer Amazon pattern is consistent across regional and global climate models and parameterized versus resolved convectionCorresponding author: Baird Langenbrunner, blangenb@uci.edu EarthArXiv PREPRINTEarthArXiv PREPRINT of confidential manuscript submitted to Earth's Future AbstractEarth system models predict a zonal dipole of precipitation change over tropical South America, with decreases over the Amazon and increases over the Andes. Much of this has been attributed to the physiological response of the rainforest to elevated CO 2 , which describes a basin-wide reduction in stomatal conductance and transpiration. While robust in Earth system model experiments, details of the underlying atmospheric mechanismspecifically how it evolves in the context of land-atmosphere interaction and the diurnal cycle-are unresolved. We investigate this using idealized model simulations and find that within 24 hours of a CO 2 increase, changes occur over the Amazon that engender synoptic timescale feedbacks. Decreased evapotranspiration from the rainforest throttles near-surface moisture, inducing a drier, warmer, and deeper boundary layer. Above this, enhanced turbulent diffusivity increases vapor in the lower free troposphere. Together, these processes reduce convective activity and cause immediate decreases in Amazon rainfall. Over the synoptic timescale, these changes leave behind lower tropospheric moisture, which is advected westward by the background jet and increases Andean precipitation. This produces a dipole of precipitation change consistent across global and regional models as well as parameterized and resolved convection, though details are sensitive to model topography and boundary layer formulation. The mechanism reported here stresses the importance of fast timescale processes affecting stability over a period of hours that can influence longer-term vegetation-climate interactions. These results help clarify the Amazon's physiological response to rising CO 2 and provide insight into possible causes of historical model biases and end-of-century uncertainty in this region.

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“…Back‐trajectory analyses using these methods can show water vapor sources and transport pathways for a precipitation event in detail (e.g., Bracken, Rajagopalan, Alexander, & Gangopadhyay, ; Dirmeyer, Wei, Bosilovich, & Mocko, ; Gimeno et al, ; Sodemann, Schwierz, & Wernli, ; Tan, Gan, & Chen, ). Because the Lagrangian methods are a computationally inexpensive alternative that can be run for large areas and long time periods (Winschall, Pfahl, Sodemann, & Wernli, ), various Lagrangian tracking methods have been used to track water vapor transport pathways, and their underlying atmospheric circulation patterns were examined for extreme precipitation events over the world (Drumond et al, ; Nieto, Ciric, Vázquez, Liberato, & Gimeno, ; Nieto & Gimeno, ), such as the western U.S. (Alexander et al, ; Bracken et al, ), Canada (Tan, Gan, & Chen, ), South China (Chu et al, ), Central America (Durán‐Quesada et al, ), South America (Staal et al, ), eastern Australia (Boschat et al, ), and Saudi Arabia (de Vries et al, ). The composite of weather processes and large‐scale circulation shows the driving forces of atmospheric moisture transport, so spatiotemporal variability of regional precipitation extremes can be attributed to variability of water vapor sources and transport pathways (Bracken et al, ; Chu et al, ; Tan, Gan, & Chen, ).…”

Section: Moisture Pathways Associated With Precipitation Extremesmentioning

confidence: 99%

Global atmospheric moisture transport associated with precipitation extremes: Mechanisms and climate change impacts

et al. 2020

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The atmospheric moisture transport processes are of great importance to the occurrence and intensity of precipitation extremes. In this paper, we review the linkage between processes, including the large‐scale atmospheric circulation, atmospheric moisture transport, and extreme precipitation events. We first summarize the thermodynamic and dynamic processes and moisture transport trackings for historical precipitation extremes. We then focus on the contribution of three major atmospheric moisture transport pathways, that is, atmospheric rivers, low‐level jets, and tropical cyclones, to the occurrence and intensity of regional precipitation extremes. Studies on large‐scale atmospheric circulation driving water vapor transport for precipitation extremes over East Asia and North America were specifically reviewed for the understanding of physical mechanisms and predictability of moisture transport and extreme precipitation events. We then pay more attention to the effects of global warming on atmospheric moisture transport, and thus regional precipitation extremes from the perspectives of thermodynamic and dynamic changes of the atmosphere. In the end, we summarize future research challenges on the physical mechanisms of atmospheric moisture transport that are associated with regional precipitation extremes, especially under a warming climate. This article is categorized under: Science of Water > Water Extremes Science of Water > Hydrological Processes

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Forest-rainfall cascades buffer against drought across the Amazon

Cited by 268 publications

References 75 publications

Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?

Can We Detect Changes in Amazon Forest Structure Using Measurements of the Isotopic Composition of Precipitation?

Why does Amazon precipitation decrease when tropical forests respond to increasing CO2?

Global atmospheric moisture transport associated with precipitation extremes: Mechanisms and climate change impacts

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