Impacts of the Pacific Meridional Mode on June–August precipitation in the Amazon River Basin

Zhang, Wei; Villarini, Gabriele; Vecchi, Gabriel A.

doi:10.1002/qj.3053

Cited by 27 publications

(17 citation statements)

References 72 publications

(137 reference statements)

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“…The Atlantic warming intensified the moisture transport convergence over tropical South America, which forms deep convection and thus enhances the local rainfall. SST warming in the North Atlantic plays a crucial role in causing the observed decadal change in the western North Pacific tropical cyclone frequency (Zhang et al 2017). We must pay great attention to Atlantic SST warming.…”

Section: Conclusion and Discussionmentioning

confidence: 99%

“…In recent decades, however, the dry season has been prolonged in the southern Amazon (since 1979), which is partly driven by the SST variability of the tropical Pacific and Atlantic, and is closely related to the shift of the subtropical jet in austral winter (Fu et al 2013). Zhang et al found that precipitation surplus (deficit) in the Amazon River basin during JJA (June, July and August) can be caused by the positive (negative) Pacific Meridional Mode (Zhang et al 2017); but only the tropical Atlantic meridional SST gradient is strongly associated with southern precipitation in JJA (Good et al 2008). Moreover, with the reductions in reflective aerosol pollution in the Northern Hemisphere, the risk of dry season (July-October) severe droughts (such as the 2005 droughts) is rapidly increasing over the Amazon in the 21st century (Cox et al 2008).…”

Section: Introductionmentioning

confidence: 99%

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

Wang

Zhu

et al. 2018

Environ. Res. Lett.

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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.

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Section: Conclusion and Discussionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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

Wang

Zhu

et al. 2018

Environ. Res. Lett.

View full text Add to dashboard Cite

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“…However, it is difficult to use real-time monitoring data to explain the impacts of spring freshet and summer rainfall flooding on lake water quality, because of insufficient manual monitoring times and the impact of flood disturbance on automatic monitoring systems. Thus, model simulation techniques are now being increasingly applied to simulate the impacts of these events on both water quantity and quality in many lakes [3,21,34]. Amongst these simulation tools is the commonly used MIKE 21 software.…”

Section: Introductionmentioning

confidence: 99%

Impact of spring freshet flooding and summer rainfall flooding on the water quality of an alpine barrier lake

Li³

et al. 2020

Environ Sci Eur

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Background: Barrier lakes, formed by river interception, are particularly influenced by the upstream river. As such, spring freshet flooding and summer rainfall flooding due to wet precipitation (e.g. snow and rainfall) may sharply increase the concentrations of nitrogen, phosphorous, and carbon compounds in barrier lakes. Too much nutrients will lead to lake eutrophication. In this study, we used Lake Jingpo, the world's second largest alpine barrier lake, to examine the impact of spring freshet flooding and summer rainfall flooding on its water quality by building a hydrodynamic water quality model with MIKE 21. Results: The MIKE 21 HD hydrodynamic model and MIKE 21 AD convection and diffusion module were calibrated using meteorological data, hydrological data, and water quality data collected in 2018. All errors were in the acceptable range. According to model simulation results, the flow velocity in Lake Jingpo is generally weak (mostly lower than 0.015 m/s), but it increases to 0.045 m/s and above during spring freshet flooding (April-May) and summer rainfall flooding (August-September), which is much higher than in other months. The flow volume of its largest inflowing river reaches 4.81 × 10 8 m 3 , 29.77 × 10 8 m 3 , and 58.4 × 10 8 m 3 during spring freshet flooding, summer rainfall flooding, and 30-year frequency rainfall flooding period, respectively. The longest diffusion distances from the lake mouth to the downstream way are 16.3 km, 33.1 km, and 43.6 km during the spring freshet flooding, summer rainfall flooding, and 30-year frequency rainfall flooding period, respectively. A larger amount of precipitation leads to longer diffusion distances and increased concentrations of total nitrogen (TN), total phosphorous (TP), chemical oxygen demand (COD Mn), and ammonia-nitrogen (NH 4-N) in the lake. Conclusions: The sudden increase in water volume during spring flooding and summer rainfall flooding led to the rapid spread of nutrients and pollutants carried by the water into the barrier lake, resulting in a deterioration of lake water quality. In addition to pollution source control measures, ecological restoration, and the construction of a buffer system in the catchment are very important measures to effectively improve the buffer capacity of barrier lakes in light of spring freshet flooding and summer rainfall flooding.

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“…However, it is difficult to use real-time monitoring data to explain the impacts of spring freshet and summer rainfall flooding on lake water quality, because of insufficient manual monitoring times and the impact of flood disturbance on automatic monitoring systems. Thus, model simulation techniques are now being increasingly applied to simulate the impacts of these events on both water quantity and quality in many lakes (Moore, 2007;Chen et al, 2015;Zhang et al, 2017). Among these simulation tools is the commonly used MIKE 21 software.…”

Section: Introductionmentioning

confidence: 99%

Impact of Spring Freshet Flooding and Summer Rainfall Flooding on the Water Quality of an Alpine Barrier Lake

LI³

et al. 2020

Preprint

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Background: Barrier lakes, formed by river interception, are particularly influenced by the upstream river. As such, spring freshet flooding and summer rainfall flooding due to wet precipitation (e.g. snow and rainfall) may sharply increase the concentrations of nitrogen, phosphorous and carbon compounds in barrier lakes. Too much nutrients will lead to lake eutrophication. In this study, we used Lake Jingpo, the world’s second largest alpine barrier lake, to examine the impact of spring freshet flooding and summer rainfall flooding on its water quality by building a hydrodynamic water-quality model with MIKE 21. Results:The MIKE 21 HD hydrodynamic model and MIKE 21 AD convection and diffusion module were calibrated using meteorological data, hydrological data, and water quality data collected in 2018. All errors were in the acceptable range. According to model simulation results, the flow velocity in Lake Jingpo is generally weak (mostly lower than 0.015 m/s), but it increases to 0.045 m/s and above during spring freshet flooding (April–May) and summer rainfall flooding (August–September), which is much higher than in other months. The flow volume of its largest inflowing river reaches 4.81×108 m3, 29.77×108 m3, and 58.4×108 m3 during spring freshet flooding, summer rainfall flooding, and 30-year frequency rainfall flooding period, respectively. The longest diffusion distances from the lake mouth to the downstream way are 16.3 km, 33.1 km, and 43.6 km during the spring freshet flooding, summer rainfall flooding, and 30-year frequency rainfall flooding period, respectively. A larger amount of precipitation leads to longer diffusion distances and increased concentrations of total nitrogen (TN), total phosphorous (TP), chemical oxygen demand (CODMn), and ammonia-nitrogen (NH4-N) in the lake. Conclusions: The sudden increase in water volume during spring flooding and summer rainfall flooding led to the rapid spread of nutrients and pollutants carried by the water into the barrier lake, resulting in a deterioration of lake water quality. In addition to pollution source control measures, ecological restoration and the construction of a buffer system in the catchment are very important measures to effectively improve the buffer capacity of barrier lakes in light of spring freshet flooding and summer rainfall flooding.

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Impacts of the Pacific Meridional Mode on June–August precipitation in the Amazon River Basin

Cited by 27 publications

References 72 publications

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

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

Impact of spring freshet flooding and summer rainfall flooding on the water quality of an alpine barrier lake

Impact of Spring Freshet Flooding and Summer Rainfall Flooding on the Water Quality of an Alpine Barrier Lake

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