Conjoint Analysis of Surface and Atmospheric Water Balances in the Andes‐Amazon System

Abstract

Surface and atmospheric water balances analysis for Amazon River basin at monthly time scale are performed with an emphasis on the linkages between the Andes and low-lying Amazonia. Analyses are performed using observational and reanalysis data covering five different periods of analysis (depending on length of evapotranspiration data sets) for the entire basin, major subcatchments, and for the Andes and low-lying Amazonia. Results for the entire basin show a state close to balance within tolerance, while the spatial disaggregation produced a less clear picture, presenting major discrepancies between observations and reanalysis data sets. The atmospheric budget exhibits no closure and positive residuals regardless of data set, with the magnitude of residuals for the entire Amazon basin highly dependent on evapotranspiration data source. The imbalance between the two water budgets (14%-16%) is driven by higher values of runoff and by an abrupt change in runoff when changing from dry to wet seasons in the Amazon. We unveil two shortcomings of the available data, namely poor quality in the representation of surface processes by reanalysis, and flaws and scarcity of information in the high Andes that induce uncertainties and errors in both water budgets. The results of the present study highlight the importance of the Andean region for the hydrological integrity of the entire Amazon River basin. Our results confirm the paramount importance of the joint analysis of atmospheric and surface water budgets at the basin level with respect to achieving a complete understanding of the whole hydrological cycle at the continental scale.

Atmospheric Moisture Pathways to the Highlands of the Tropical Andes: Analyzing the Effects of Spectral Nudging on Different Driving Fields for Regional Climate Modeling

“…For more details on the South American monsoon system, see [5,[8][9][10][11][12], among others. As described by previous studies, this coupled hydro-climatic system between the Amazon basin and the Andes highlands is highly endangered by global change [2,[13][14][15], which alters the evapotranspiration and moisture distribution. To understand the atmospheric moisture transport towards the Andean range on a regional scale, as well as the recycling of the water over the highlands, regional climate models (RCMs) provide a useful tool.…”

“…The Amazon-Andes transition in tropical South America represents an extensive hydro-climatic system coupled by the main large-scale circulation features and the barrier effect of the topography [1][2][3]. Over the Amazon basin, large amounts of moisture are released into the atmosphere by evapotranspiration.…”

Hydroclimate of the Andes Part I: Main Climatic Features

“…The Amazon region exports water vapor and nutrients to the Andes through the moisture-laden trade winds (e.g., Garreaud, 1999;Poveda et al, 2006Poveda et al, , 2014Zemp et al, 2017). The ascent of these winds owing to the orographic effect of the Andes, favors convection and high intensity rainfall rates over the eastern piedmont (e.g., Espinoza et al, 2009bEspinoza et al, , 2015Chavez and Takahashi, 2017;Junquas et al, 2018;Kumar et al, 2019), which in turn produces the river runoff draining sediments, pollutants, and nutrients downstream to the Amazon lowlands (Poveda et al, 2006;McClain and Naiman, 2008;Espinoza et al, 2009a;Moquet et al, 2011;Molina-Carpio et al, 2017;Builes-Jaramillo and Poveda, 2018).…”

“…Multiannual rainfall variability in the Amazon basin, including extreme hydroclimatic events, has been mainly attributed to the sea surface temperatures (SST) variations in both the tropical Pacific and Atlantic oceans, with seasonal and regional specificities. In addition, a reduced vegetation cover in the southern Amazon also contributes to a more frequent occurrence of longer dry seasons over this region (for more details see Debortoli et al, 2015;Marengo and Espinoza, 2016;Barichivich et al, 2018;Builes-Jaramillo and Poveda, 2018;Espinoza et al, 2019;Leite-Filho et al, 2019;Ruiz-Vasquez et al, submitted, among others).…”

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).…”