Forest‐Induced Exponential Growth of Precipitation Along Climatological Wind Streamlines Over the Amazon

Abstract

The Amazon forests and climatological precipitation patterns in South America are interrelated. A fundamental question is how these patterns depend on the presence of forests. Here we investigate this relationship by studying how precipitation varies with distance from the ocean along wind streamlines linking the Atlantic Ocean to northwestern and southern South America through the Amazon forests. Through a robust observation‐based analysis, we found that precipitation exponentially increases with distance from the ocean along wind streamlines flowing over forests, while it exponentially decreases downwind of the forests. These patterns are consistent with multiple mechanisms through which forests influence the transport of atmospheric moisture and precipitation production over the continent. We propose a conceptual explanation of this forest influence based on the atmospheric water balance. Our results imply that a major consequence of the degradation or loss of forests may be a disruption of these mechanisms, with widespread impacts on continental precipitation.

The Forest Effects on the Isotopic Composition of Rainfall in the Northwestern Amazon Basin

“…The seasonal precipitation over large parts of the Amazon region is mainly characterized by wet conditions in the austral summer, associated with the active phase of the South American Monsoon System (Vera et al, 2006;Zhou & Lau, 1998) and a dry season in austral winter, in the absence of the South American Monsoon System forcing. Moreover, several studies have shown that the Amazon basin itself constitutes a major moisture source for the region, driven by the hydrologic regime of the rainforest (Builes-Jaramillo & Poveda, 2018;Drumond et al, 2014;Molina et al, 2019;Salati et al, 1979). In fact, the forest induces dry season rainfall, necessary to sustain itself when oceanic moisture supply is limited (Staal et al, 2018).…”

The southern Amazon rainy season: The role of deforestation and its interactions with large‐scale mechanisms

“…The southern Amazon is one of the most rapidly developing agricultural frontiers in the world, having experienced high rates of conversion of forest to croplands and pasturelands (Salazar et al, 2007;Instituto Nacional de Pesquisas Espaciais, 2014). Previous studies have demonstrated that these intense land use and land cover changes affect the regional precipitation (Lean et al, 1996;Costa and Foley, 2000;Davidson et al, 2012;Debortoli et al, 2015;Boers et al, 2017;Agudelo et al, 2019;Leite-Filho et al, 2019;Molina et al, 2019). These impacts are potentially important for the region, as some of its main economic activities, including agriculture, are highly dependent on climate (Sumila et al, 2017).…”

Tipping the ENSO into a permanent El Niño can trigger state transitions in global terrestrial ecosystems

“…A PEN-induced dieback in the Amazon could tip the rainforest from a sink of carbon to a possible source (Davidson et al, 2012). This could in turn amplify the magnitude of extreme hydrological and weather events that occur during El Niño, such as droughts, in a positive-feedback-like manner (Zemp et al, 2017;Salazar et al, 2018), as well as disrupt mechanisms of river flow regulation (Salazar et al, 2018;Mercado-Bettin et al, 2019) and continental precipitation distribution (Molina et al, 2019). Near-synchronous effects of this sort between different tipping elements could give rise to a "tipping cascade" that could contribute to a planetary-scale state shift (Lenton and Williams, 2013 forest collapse in most of the Amazon, our results also agree with Betts et al (2008) that some areas in western Amazonia (adjacent to the Andes) are less vulnerable and could act as a refuge for biodiversity.…”