The Atmospheric Branch of the Hydrological Cycle over the Negro and Madeira River Basins in the Amazon Region

Rogert Sorí,José Marengo,Raquel Nieto,Anita Drumond,Luis Gimeno

doi:10.3390/w10060738

Abstract

The Amazon region, in South America, contains the largest rainforest and biodiversity in the world, and plays an important role in the regional and global hydrological cycle. In the present study, we identified the main sources of moisture of two subbasins of the Amazon River Basin, the Negro and Madeira River Basins respectively. The source-sink relationships of atmospheric moisture are investigated. The analysis is performed for the period from 1980–2016. The results confirm two main oceanic moisture sources for both basins, i.e., oceanic regions in the Tropical North and South Atlantic oceans. On the continents are, the Negro River Basin itself, and nearby regions to the northeast. For the Madeira River Basin, the most important continental sources are itself, and surrounding regions of the South American continent. Forward-trajectory analysis of air masses over the source regions is used to compute the moisture contribution to precipitation over basins. Oceanic (continental) sources play the most important role in the Negro River Basin (Madeira River Basin). The moisture contribution from the Tropical North Atlantic region modulates the onset and demise of the rainy season in the Negro River Basin; while the moisture contribution from the rest of the Amazon River Basin, the Madeira Basin itself, and Tropical South America leads to the onset of the rainy season in the Madeira River Basin. These regions also played the most important role in decreasing the moisture supply during most severe dry episodes in both basins. During ‘’El Niño’’, generally occurs a reduction (increase) of the moisture contribution to the Negro River Basin (Madeira River Basin; mainly from April to August) from almost all the sources, causing a decrease in the precipitation. Generally, the contrary occurs during ‘’La Niña’’.

Highlights

The Amazon River Basin (ARB) (Figure 1) hosts the world’s largest tropical rainforest and drainage basin on the planet
April was a transitional month; the maximum precipitation occurred over the northern half of the ARB, but major rainfall was favoured over the Negro River Basin (NRB) in May and June
In October, the P increased over the southeast of the ARB; this phenomenon was best observed in November and December

Summary

Introduction

The Amazon River Basin (ARB) (Figure 1) hosts the world’s largest tropical rainforest and drainage basin on the planet. It is an important source of natural resources for human economic development and is characterised by large biodiversity. American continent and the discharge of the Amazon River (AR) accounts for almost one-fifth of the total discharge of all rivers of the world [1]. The most important subbasins are the Negro and Madeira River basins (NRB, MRB; Figure 1) in the north and southwest, respectively. The Negro and Madeira Rivers (NR and MR respectively) are the most important Amazonas tributaries, contributing more than one-third of the total water discharge [1]

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Conclusion