Importance in Shifting Circulation Patterns for Dry Season Moisture Sources in the Brazilian Amazon

Abstract

Forests influence climate through exchanges of water, energy, and chemicals with the atmosphere (Bonan, 2008). Evapotranspiration (ET) from vegetation is recycled through the atmosphere as water vapor and reaches downwind locations as precipitation (Keys et al., 2012;Lettau et al., 1979). Globally, more than half of terrestrial evaporated moisture rains back again over land (Tuinenburg et al., 2020), and for the Brazilian Amazon, forest ET accounts for one-third to more than half of the total rainfall (Satyamurty et al., 2013). During the wet season, the southwestern region of the Amazon basin provides rainfall directly to the La Plata basin through moisture recycling, dispersing moisture from the Amazon basin to the La Plata basin (Zemp et al., 2014).The Amazon Rainforest is experiencing deforestation, particularly in the southeastern border of the forest, called the "arc of deforestation." Forests have deep roots that access water in deeper soil layers and can maintain ET during droughts, buffering against precipitation variations (Da Rocha et al., 2009;Mu, Biggs, & De Sales, 2021;O'Connor et al., 2021). Pasture grasses, which account for most post-deforestation cover in the Amazon, have shallow roots and lower dry season ET, so deforestation may amplify drought conditions (Mu, Biggs, &

Changes in atmospheric circulation and evapotranspiration are reducing rainfall in the Brazilian Cerrado

“…Regarding Cerrado, the evapotranspiration reduction during the DS and the BWS acts in synergy with omega increase, causing an intensification and expansion of the dry period in the Cerrado 30 . The combination of effects from evapotranspiration reduction and moisture transference linked to changes in atmospheric circulation are also discussed and recognized as important by a recent study that evaluated the rainfall reduction during the dry season in the southwest of the Amazon in the last 40 years 39 . Although we have not been able to quantify the role of land cover change in this reduction in evapotranspiration, recent studies formally demonstrate these using different methodologies 5 , 6 , 32 .…”

Changes in atmospheric moisture transport over tropical South America: an analysis under a climate change scenario

“…The projections discussed here correspond to a "worse" case emission scenario depicted by the RCP8.5 (Riahi et al 2011). Mu et al (2021) show that the atmospheric moisture supply from forests mitigate drought in the Brazilian Amazon, although this mechanism can be compensated due to circulation changes (Mu et al 2023). Thus, considering the land cover change used by the RCP8.5, the projection of reductions in the contributions to P from the main atmospheric moisture sources, the reductions of total P, and the reductions of recycled P over the Amazon during the dry season could be linked to land cover and atmospheric transport changes.…”

Moisture sources of precipitation over the Pearl River Basin in South China

“…A source region that contributes atmospheric moisture to a sink region's precipitation is called precipitationshed (Keys et al, 2012). In recent years, the WAM‐2layers model has been extensively utilized to quantify moisture contributions to a target region from different precipitationsheds (Keys et al, 2018; Mu et al, 2023). In addition, this model helps to investigate the moisture sources of anomalous precipitation, thereby improving our understanding of the relationship between regional precipitation characteristics and large‐scale atmospheric circulation during extreme weather events (Benedict et al, 2021; Liu et al, 2020; Zhao et al, 2022).…”