Interannual variability of Tropical Atlantic and its influence on drought and flood events in the Amazon Basin

2020 ◽  
Author(s):  
Katherine Lisbeth Ccoica López ◽  
Ricardo Hallak ◽  
Victor Raúl Chavez Mayta
Keyword(s):  
North Atlantic ◽  
Rainy Season ◽  
Amazon Basin ◽  
South Atlantic ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Flood Events ◽  
Drought And Flood ◽  
The North ◽  
Tropical North Atlantic

<p>The Tropical Pacific and Tropical Atlantic Ocean modulate the interannual precipitation over the Amazon region and the decadal and interdecadal variation as well. During El Niño Southern Oscillation (ENSO), below-average rainfall is recorded in the North and Northeast of the Basin, while deficit of precipitation is observed in the West and South. On the other hand, during La Niña years, rainfall is above of normal in the North and Northeast of Amazon Basin. However, there are also drought events, such as in 1964 and 2005, unrelated to the El Niño event, but influenced by warm conditions in the Tropical North Atlantic. In fact, the exceptional drought recorded in 2010 was influenced by a combined effect of the El Niño event during the peak of rainy season, followed by warm conditions in the Tropical North Atlantic during final of rainy season and dry season.</p><p>Therefore, the main aim of this study is exploring the Atlantic Sea Surface Temperature (SST) condition in modulating patterns that influence the development of drought and flood events in the Amazon Basin. First of all, the Atlantic Ocean is divided into Tropical North Atlantic (TNA), Tropical South Atlantic (TSA) and Subtropical South Atlantic (STSA), to analyze the behavior of each region separately. Atlantic Index, in each region, is the first principal component (PC1) time series, which comes from the empirical orthogonal function (EOF) analysis applied to Hadley Center Global Sea Ice and Sea Surface Temperature (HadISST) dataset for the 1870-2107 period. The Tropical North Atlantic, Tropical South Atlantic and Subtropical South Atlantic indices show the main years when drought and flood events reaching the Amazon Basin (droughts in 2005, 2010 and 2015, and floods in 2009 and 2012, mainly), and 5-years moving correlations indicate that these three ocean basin have been coupled and decoupled periodically each other in the last century.</p><p>The equatorial Pacific, North Atlantic and South Atlantic indices were also correlated with rainfall over the Amazon for three databases: the Tropical Rainfall Mission Measurements (TRMM), the Global Precipitation Climatology Centre (GPCC) and the HyBAm Observed Precipitation. All three databases showed the same results. An increase of the SST in Eastern Pacific influences in low precipitation over the central and west of the Amazon Basin during the rainy season (December to February), increase of the SST in Central Pacific influences for droughts over the northeast region and the TSA influences in the central Amazon. Increase of the SST in TNA and STSA influences mainly in the dry season (May to September), intensifying it. TNA is responsible for precipitation below normal over the central and west Amazon Basin, while STSA only influences in the central region of the basin. Finally, analysis of extreme events indicate that droughts and floods in the Amazon are intensified (de-intensified) if we consider warm (cold) phases of the AMO (Atlantic Multidecadal Oscillation) and the PDO (Pacific Decadal Oscillation).</p>

scholarly journals Reservoir Ages in the Western Tropical North Atlantic from One Coral off Martinique Island (Lesser Antilles)

Radiocarbon ◽  
2018 ◽  
Vol 60 (2) ◽  
pp. 639-652
Author(s):  
Martine Paterne ◽  
Nathalie Feuillet ◽  
Guy Cabioch ◽  
Elsa Cortijo ◽  
Dominique Blamart ◽  
...  
Keyword(s):  
North Atlantic ◽  
Atlantic Coast ◽  
South Atlantic ◽  
Sea Surface ◽  
Lesser Antilles ◽  
Moderate Increase ◽  
The South ◽  
Mean Values ◽  
The North ◽  
Tropical North Atlantic

AbstractSea surface reservoir ages (R) are reported from radiocarbon (14C) measurements of the annual growth bands of coral Siderastrea siderea collected on the Atlantic coast off Martinique Island, in the Lesser Antilles volcanic arc. Mean values of R are similar between 1835 and 1845 during pre-anthropogenic times at 385±30 yr and between 1895 and 1905 at 382±20 yr when there was a huge eruption from the Montagne Pelée volcano in 1902–1903. Limited 14C aging of sea surface (~40 yr) may be due to enhanced volcanic activity. Variability of R is slightly greater during 1835–1845 than during 1895–1905. It is linked to a moderate increase of ∆14C of 5‰, strengthened by a clear increase of δ18O of 0.4‰. This is attributed to a decrease of the northward advection of the South Atlantic Waters into the western tropical North Atlantic and Caribbean Sea and relative enhanced westward flux of the tropical North Atlantic surface waters, the southern waters having lower values of 14C and δ18O than the North Atlantic ones. From 1835 to 1845, the fraction of the South Atlantic Waters transported up to Martinique Island was reduced from 25% to 15%.

scholarly journals Meridional distribution of aerosol optical thickness over the tropical Atlantic Ocean

2014 ◽  
Vol 14 (16) ◽  
pp. 23309-23339 ◽  
Author(s):  
P. Kishcha ◽  
A. M. da Silva ◽  
B. Starobinets ◽  
C. N. Long ◽  
O. Kalashnikova ◽  
...  
Keyword(s):  
North Atlantic ◽  
Optical Thickness ◽  
South Atlantic ◽  
Aerosol Optical Thickness ◽  
Global Ocean ◽  
Limited Area ◽  
Tropical Atlantic ◽  
The North ◽  
Tropical North Atlantic ◽  
The North Atlantic

Abstract. Previous studies showed that, over the global ocean, there is hemispheric asymmetry in aerosols and no noticeable asymmetry in cloud fraction (CF). In the current study, we focus on the tropical Atlantic (30° N–30° S) which is characterized by significant amounts of Saharan dust dominating other aerosol species over the North Atlantic. Over a limited area such as the tropical Atlantic, our study showed that strong meridional asymmetry in dust aerosols was accompanied by meridional CF asymmetry, by contrast to the global ocean. During the 10 yr study period (July 2002–June 2012), NASA Aerosol Reanalysis (aka MERRAero) showed that, when the meridional asymmetry in dust aerosol optical thickness (AOT) was the most pronounced (particularly in July), dust AOT averaged separately over the tropical North Atlantic was one order of magnitude higher than dust AOT averaged over the tropical South Atlantic. In the presence of such strong meridional asymmetry in dust AOT in July, CF averaged separately over the tropical North Atlantic exceeded CF averaged over the tropical South Atlantic by 20%. In July, along the Saharan Air Layer, Moderate Resolution Imaging Spectroradiometer (MODIS) CF data showed significant cloud cover (up to 0.8–0.9), which contributed to above-mentioned meridional CF asymmetry. Both Multi-Angle Imaging SpectroRadiometer (MISR) measurements and MERRAero data were in agreement on seasonal variations in meridional aerosol asymmetry. Meridional asymmetry in total AOT over the Atlantic was the most pronounced between March and July, when dust presence over the North Atlantic was maximal. In September and October, there was no noticeable meridional asymmetry in total AOT over the tropical Atlantic.

The Impact of Sea Surface Temperature Biases on North American Precipitation in a High-Resolution Climate Model

2020 ◽  
Vol 33 (6) ◽  
pp. 2427-2447 ◽  
Author(s):  
Nathaniel C. Johnson ◽  
Lakshmi Krishnamurthy ◽  
Andrew T. Wittenberg ◽  
Baoqiang Xiang ◽  
Gabriel A. Vecchi ◽  
...  
Keyword(s):  
North America ◽  
Surface Temperature ◽  
North Atlantic ◽  
North American ◽  
North Pacific ◽  
Climate Model ◽  
Sea Surface ◽  
Tropical Atlantic ◽  
Western North America ◽  
The North

AbstractPositive precipitation biases over western North America have remained a pervasive problem in the current generation of coupled global climate models. These biases are substantially reduced, however, in a version of the Geophysical Fluid Dynamics Laboratory Forecast-Oriented Low Ocean Resolution (FLOR) coupled climate model with systematic sea surface temperature (SST) biases artificially corrected through flux adjustment. This study examines how the SST biases in the Atlantic and Pacific Oceans contribute to the North American precipitation biases. Experiments with the FLOR model in which SST biases are removed in the Atlantic and Pacific are carried out to determine the contribution of SST errors in each basin to precipitation statistics over North America. Tropical and North Pacific SST biases have a strong impact on northern North American precipitation, while tropical Atlantic SST biases have a dominant impact on precipitation biases in southern North America, including the western United States. Most notably, negative SST biases in the tropical Atlantic in boreal winter induce an anomalously strong Aleutian low and a southward bias in the North Pacific storm track. In boreal summer, the negative SST biases induce a strengthened North Atlantic subtropical high and Great Plains low-level jet. Each of these impacts contributes to positive annual mean precipitation biases over western North America. Both North Pacific and North Atlantic SST biases induce SST biases in remote basins through dynamical pathways, so a complete attribution of the effects of SST biases on precipitation must account for both the local and remote impacts.

scholarly journals Teleconnection mechanisms of northeast Brazil droughts: modeling and empirical evidence

2008 ◽  
Vol 23 (2) ◽  
pp. 115-125 ◽  
Author(s):  
Fred Kucharski ◽  
Dierk Polzin ◽  
Stefan Hastenrath
Keyword(s):  
Numerical Modelling ◽  
North Atlantic ◽  
Wave Train ◽  
Vertical Motion ◽  
Equatorial Pacific ◽  
Intertropical Convergence Zone ◽  
Sea Surface ◽  
North Atlantic Subtropical High ◽  
The North ◽  
Tropical North Atlantic

Targeted numerical modelling experimaents are conducted to complement the previous empirical diagnostics of circulation mechanisms leading from sea surface temperature (SST) departures in the equatorial Pacific in January to anomalies in the March-April rainy season of Brazil's Nordeste. A weak interhemispheric northward directed SST gradient in the Atlantic favors a more southerly position of the hydrostatically controlled low pressure trough, embedded in which is the Intertropical Convergence Zone (ITCZ), which is the main rainbearing system for the Nordeste. In addition, anomalously warm waters in the equatorial Pacific in January tend to be followed by Nordeste drought. The underlying chain of causalities has been explored by empirical diagnostics and numerical modelling. During El Nino years, an upper-tropospheric wave train extends from the equatorial eastern Pacific to the tropical North Atlantic, affecting the patterns of upper-tropospheric topography and divergence, and hence of vertical motion over the Atlantic. This leads to a weaker meridional pressure gradient on the equatorward flank of the North Atlantic subtropical high, weaker North Atlantic tradewinds, an anomalously far northerly ITCZ position and thus Nordeste drought. The previous empirical diagnostics are overall supported by the modelling experiments.

Influence of the Meridional Overturning Circulation on Tropical Atlantic Climate and Variability

2008 ◽  
Vol 21 (6) ◽  
pp. 1403-1416 ◽  
Author(s):  
Reindert J. Haarsma ◽  
Edmo Campos ◽  
Wilco Hazeleger ◽  
Camiel Severijns
Keyword(s):  
Mixed Layer ◽  
North Atlantic ◽  
Ocean Model ◽  
South Atlantic ◽  
Meridional Overturning Circulation ◽  
Tropical Atlantic ◽  
Overturning Circulation ◽  
The North ◽  
Meridional Overturning ◽  
The North Atlantic

Abstract The influence of the meridional overturning circulation on tropical Atlantic climate and variability has been investigated using the atmosphere–ocean coupled model Speedy-MICOM (Miami Isopycnic Coordinate Ocean Model). In the ocean model MICOM the strength of the meridional overturning cell can be regulated by specifying the lateral boundary conditions. In case of a collapse of the basinwide meridional overturning cell the SST response in the Atlantic is characterized by a dipole with a cooling in the North Atlantic and a warming in the tropical and South Atlantic. The cooling in the North Atlantic is due to the decrease in the strength of the western boundary currents, which reduces the northward advection of heat. The warming in the tropical Atlantic is caused by a reduced ventilation of water originating from the South Atlantic. This effect is most prominent in the eastern tropical Atlantic during boreal summer when the mixed layer attains its minimum depth. As a consequence the seasonal cycle as well as the interannual variability in SST is reduced. The characteristics of the cold tongue mode are changed: the variability in the eastern equatorial region is strongly reduced and the largest variability is now in the Benguela, Angola region. Because of the deepening of the equatorial thermocline, variations in the thermocline depth in the eastern tropical Atlantic no longer significantly affect the mixed layer temperature. The gradient mode remains unaltered. The warming of the tropical Atlantic enhances and shifts the Hadley circulation. Together with the cooling in the North Atlantic, this increases the strength of the subtropical jet and the baroclinicity over the North Atlantic.

scholarly journals The Physical Basis for Predicting Atlantic Sector Seasonal-to-Interannual Climate Variability*

2006 ◽  
Vol 19 (23) ◽  
pp. 5949-5970 ◽  
Author(s):  
Yochanan Kushnir ◽  
Walter A. Robinson ◽  
Ping Chang ◽  
Andrew W. Robertson
Keyword(s):  
Climate Variability ◽  
North Atlantic ◽  
El Niño ◽  
El Nino ◽  
South Atlantic ◽  
Tropical Atlantic ◽  
Coupled Models ◽  
Atlantic Sector ◽  
The North ◽  
The North Atlantic

Abstract This paper reviews the observational and theoretical basis for the prediction of seasonal-to-interannual (S/I) climate variability in the Atlantic sector. The emphasis is on the large-scale picture rather than on regional details. The paper is divided into two main parts: a discussion of the predictability of the North Atlantic Oscillation (NAO)—the dominant pattern of variability in the North Atlantic—and a review of the tropical Atlantic prediction problem. The remote effects of El Niño are also mentioned as an important factor in Atlantic climate variability. Only a brief discussion is provided on the subject of South Atlantic climate predictability. Because of its chaotic dynamical nature, the NAO and its related rainfall and temperature variability, while highly significant over Europe and North America, are largely unpredictable. This also affects the predictive skill over the tropical Atlantic, because the NAO interferes with the remote influence of El Niño. That said, there appears to be an insufficiently understood, marginal signal in the NAO behavior that may be predictable and thus useful to certain end users. It is manifested in the deviation of the NAO temporal behavior from first-order autoregressive behavior. Tropical Atlantic climate variability centers on the sensitivity of the marine ITCZ to remote forcing from the equatorial Pacific and interactions with underlying sea surface temperature (SST) variability. Both mechanisms are potentially predictable—that is, given the underlying SSTs and the strength of El Niño, one could determine with a high degree of skill the anomalies in ITCZ position and intensity. However, local SSTs are easily affected by largely unpredictable North and South Atlantic phenomena, such as the NAO. In addition, the local ocean–atmosphere coupling in the Atlantic acts on relatively short time scales. Thus, in reality the level of skill indicated by forced model simulations are difficult to achieve. The use of coupled models may improve the prospects of tropical Atlantic prediction.

Observed seasonal regimes of North-South Atlantic Ocean interbasin exchange

2019 ◽  
Author(s):  
Hamed D. Ibrahim
Keyword(s):  
North Atlantic ◽  
Climate Models ◽  
South Atlantic ◽  
Meridional Overturning Circulation ◽  
Volume Flux ◽  
The South ◽  
The North ◽  
Basin Scale ◽  
Interbasin Exchange ◽  
North And South

North and South Atlantic lateral volume exchange is a key component of the Atlantic Meridional Overturning Circulation (AMOC) embedded in Earth’s climate. Northward AMOC heat transport within this exchange mitigates the large heat loss to the atmosphere in the northern North Atlantic. Because of inadequate climate data, observational basin-scale studies of net interbasin exchange between the North and South Atlantic have been limited. Here ten independent climate datasets, five satellite-derived and five analyses, are synthesized to show that North and South Atlantic climatological net lateral volume exchange is partitioned into two seasonal regimes. From late-May to late-November, net lateral volume flux is from the North to the South Atlantic; whereas from late-November to late-May, net lateral volume flux is from the South to the North Atlantic. This climatological characterization offers a framework for assessing seasonal variations in these basins and provides a constraint for climate models that simulate AMOC dynamics.

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