The strengthening of Amazonian precipitation during the wet season driven by tropical sea surface temperature forcing

Abstract

Amazonian rainfall plays a critical role in the global climate system and the hydrological cycle. It is thus important to quantify changes in the Amazonian rainfall and clarify its mechanism. Previous studies indicate that the interannual variability of Amazonian precipitation could be largely attributed to variabilities in the South American monsoon system and the El Niño Southern Oscillation. However, the trend of the wet season tropical Amazonian precipitation during recent decades is not very well investigated. In this study, by combining both satellite and in situ observations, it is revealed that tropical Amazonian precipitation has significantly increased by ∼180 to 600 mm (in different datasets) in the wet season during the satellite era from 1979 to 2015. We then use a state-of-the-art atmospheric model to simulate the impact of the tropical sea surface temperatures (SSTs) on the precipitation changes. Results show that the multidecadal warming of the tropical Atlantic has contributed more than half of this precipitation change over the past three decades, while the east Pacific cooling plays a secondary role. We finally combine the simulation results and the reanalysis data to investigate the mechanisms of this process, i.e. the SST variability dramatically increases the convergence of the moisture transport over the Amazon region. The precipitation changes over the Amazon region largely impact on the local hydrological cycle and the ecosystem, and have important impacts on the global climate system by mediating the teleconnection between the Pacific and the Atlantic oceans. Our results show that the long-term change in the wet season Amazonian precipitation is important and deserves further investigation and discussion.

Pacific and Atlantic multidecadal variability relations to the El Niño events and their effects on the South American rainfall

“…Here, we found that the combined AMO-PDO conditions and the associated interbasin cell between the equatorial Atlantic and eastern equatorial Pacific are crucial factors in defining the variations in the Walker cell. The analyses here provide additional arguments to interpret the recent findings on the increase of the Amazonian rainfall during the wet season over the 1979-2015 period (Wang et al, 2018) and on the intensification of flooding extremes over the 1903-2015 period (Barichivich et al, 2018). Wang et al (2018) attributed their results to the Atlantic warming, which intensified the moisture transport convergence over tropical SA.…”

“…The analyses here provide additional arguments to interpret the recent findings on the increase of the Amazonian rainfall during the wet season over the 1979-2015 period (Wang et al, 2018) and on the intensification of flooding extremes over the 1903-2015 period (Barichivich et al, 2018). Wang et al (2018) attributed their results to the Atlantic warming, which intensified the moisture transport convergence over tropical SA. On the other hand, Barichivich et al (2018) argued that the intensified floods were related to the strengthening of the Walker circulation, which, in turn, resulted from the Atlantic warming and tropical Pacific cooling.…”

“…The analyses here provide additional arguments to interpret the recent findings on the increase of the Amazonian rainfall during the wet season over the 1979–2015 period (Wang et al ., ) and on the intensification of flooding extremes over the 1903–2015 period (Barichivich et al ., ). Wang et al .…”

The Rise of Climate-Driven Sediment Discharge in the Amazonian River Basin

“…This means that in years with significant ENSO events, rainfall regime tends to increase in this region, which implies increased rainfall erosivity and, so, sediment rates. Accordingly, Figure 5b shows the positive change in amount rate of the precipitation during the six different months (DJFMAM) from 1979-2015 on most of the Amazon basin, and with spatial range from 30 to 100 mm per season [91]. Marengo and Espinoza Villar [36] also found that hydrological data show trends towards more extreme events across the Amazonia region during the 20th century.…”

Assessing precipitation concentration in the Amazon basin from different satellite‐based data sets

“…Therefore, the concentration of daily rainfall is a subject of great interest, since it is highly associated with the contribution of extreme precipitation (%) of certain time durations, during several days, to the total rainfall amount of the defined time interval (Alijani et al, 2008;Zhang et al, 2009;Suhaila and Jemain, 2012;Shi et al, 2013;Zubieta et al, 2017a). This point is particularly relevant in the AB, where an increase of rainy (dry) days has been identified in the north (south) part of the basin since the last two decades (e.g., Espinoza et al, 2018;Wang et al, 2018).…”