scholarly journals MJO Modulating the Activity of the Leading Mode of Intraseasonal Variability in South America

Atmosphere ◽  
2017 ◽  
Vol 8 (12) ◽  
pp. 232 ◽  
Author(s):  
Mariano Alvarez ◽  
Carolina Vera ◽  
George Kiladis
Keyword(s):  
South America ◽  
Intraseasonal Variability ◽  
Leading Mode

Intraseasonal Variability Associated with Summer Precipitation over South America Simulated by 14 IPCC AR4 Coupled GCMs

2009 ◽  
Vol 137 (9) ◽  
pp. 2931-2954 ◽  
Author(s):  
Jia-Lin Lin ◽  
Toshiaki Shinoda ◽  
Brant Liebmann ◽  
Taotao Qian ◽  
Weiqing Han ◽  
...  
Keyword(s):  
South America ◽  
General Circulation ◽  
Intraseasonal Variability ◽  
Summer Precipitation ◽  
Climate Simulation ◽  
Convergence Zone ◽  
The South ◽  
Central Pacific ◽  
South Central ◽  
Northward Propagation

Abstract This study evaluates the intraseasonal variability associated with summer precipitation over South America in 14 coupled general circulation models (GCMs) participating in the Intergovernmental Panel on Climate Change (IPCC) Fourth Assessment Report (AR4). Eight years of each model’s twentieth-century climate simulation are analyzed. Two dominant intraseasonal bands associated with summer precipitation over South America are focused on: the 40- and the 22-day band. The results show that in the southern summer (November–April), most of the models underestimate seasonal mean precipitation over central-east Brazil, northeast Brazil, and the South Atlantic convergence zone (SACZ), while the Atlantic intertropical convergence zone (ITCZ) is shifted southward of its observed position. Most of the models capture both the 40- and 22-day band around Uruguay, but with less frequent active episodes than observed. The models also tend to underestimate the total intraseasonal (10–90 day), the 40-, and the 22-day band variances. For the 40-day band, 10 of the 14 models simulate to some extent the 3-cell pattern around South America, and 6 models reproduce its teleconnection with precipitation in the south-central Pacific, but only 1 model simulates the teleconnection with the MJO in the equatorial Pacific, and only 3 models capture its northward propagation from 50° to 32°S. For the 7 models with three-dimensional data available, only 1 model reproduces well the deep baroclinic vertical structure of the 40-day band. For the 22-day band, only 6 of the 14 models capture its northward propagation from the SACZ to the Atlantic ITCZ. It is found that models with some form of moisture convective trigger tend to produce large variances for the intraseasonal bands.

Intraseasonal variability in subtropical South America as depicted by precipitation data

2007 ◽  
Vol 30 (7-8) ◽  
pp. 727-744 ◽  
Author(s):  
P. L. M. González ◽  
C. S. Vera ◽  
B. Liebmann ◽  
G. Kiladis
Keyword(s):  
South America ◽  
Intraseasonal Variability ◽  
Precipitation Data

scholarly journals Moisture transport and intraseasonal variability in the South America monsoon system

2010 ◽  
Vol 36 (9-10) ◽  
pp. 1865-1880 ◽  
Author(s):  
Leila M. V. Carvalho ◽  
Ana E. Silva ◽  
Charles Jones ◽  
Brant Liebmann ◽  
Pedro L. Silva Dias ◽  
...  
Keyword(s):  
South America ◽  
Moisture Transport ◽  
Intraseasonal Variability ◽  
The South ◽  
Monsoon System

Intraseasonal variability in South America during the cold season

2013 ◽  
Vol 42 (11-12) ◽  
pp. 3253-3269 ◽  
Author(s):  
Mariano S. Alvarez ◽  
C. S. Vera ◽  
G. N. Kiladis ◽  
B. Liebmann
Keyword(s):  
South America ◽  
Intraseasonal Variability ◽  
Cold Season

scholarly journals Intraseasonal Teleconnections between South America and South Africa

2015 ◽  
Vol 28 (23) ◽  
pp. 9489-9497 ◽  
Author(s):  
Alice M. Grimm ◽  
C. J. C. Reason
Keyword(s):  
South America ◽  
Southern Africa ◽  
Rainfall Variability ◽  
Intraseasonal Variability ◽  
Daily Rainfall ◽  
Summer Rainfall ◽  
South American ◽  
Climate Anomalies ◽  
Monsoon System ◽  
The Tropics

Abstract Teleconnection of climate anomalies between various parts of the tropics and extratropics is a well-established feature of the climate system. Building on previous work showing that a teleconnection exists between the South American monsoon system and interannual summer rainfall variability over southern Africa, this study considers intraseasonal variability over these landmasses. It is shown that strong teleconnections exist between South African daily rainfall and that over various areas of South America, with the latter leading by 4–5 days, for both winter and summer, involving regions with strong rainfall in these seasons. During the summer, the mechanisms involve both a modulation of the local Walker cell as well as extratropical Rossby wave trains. For winter, the latter mechanism is more important. While in summer tropical convective anomalies over South America play an important role, in winter the subtropics become more important. In both cases, these modulations lead to regional changes in circulation over southern Africa that are favorable for the dominant synoptic rainfall-producing weather systems such as cutoff lows and tropical extratropical cloud bands.

Rossby wave dynamics over South America explored with automatic Tropical-Extratropical cloud band identification framework

2021 ◽  
pp. 1-58
Author(s):  
Marcia T. Zilli ◽  
Neil C. G. Hart
Keyword(s):  
South America ◽  
Rossby Waves ◽  
Intraseasonal Variability ◽  
Austral Summer ◽  
South Atlantic Convergence Zone ◽  
Cloud Band ◽  
Transient Events ◽  
Upper Level ◽  
Extratropical Disturbances ◽  
The Tropics

AbstractDuring austral summer, persistent tropical-extratropical cloud bands, such as the South Atlantic Convergence Zone (SACZ) over South America (SAm), link the tropical humid areas to the subtropics. In this study, we utilize an automatic object-based methodology to identify synoptic cloudband events occurring over SAm which are responsible for almost 60% of the precipitation during the rainy season (November to March). In addition to identifying SACZ events as cloud bands persisting four or more days, the framework also highlights the relevance of transient events (i.e., events persisting for three days or less) to the climatology. The location and persistence of the cloudband events are modulated by the propagation of synoptic-scale extratropical disturbances interacting with intraseasonal variability in the basic state upper-level zonal wind. During persistent events (i.e., lasting four or more days), upper-level westerly anomalies over the subtropics favour the propagation extratropical disturbances deeper into the tropics. Conversely, transient events occur when the Bolivian High is displaced/expanded southeastward, bringing upper-level easterly winds into subtropical latitudes and blocking the propagation of Rossby waves into lower latitudes. Subsequent anomalous subtropical convection from the cloud bands result in sources of Rossby waves that interact with the basic flow, resulting in downwind enhancement or damping of the extratropical disturbances. The adopted methodology proved to be a powerful framework in demonstrating this interaction between scales, with the basic state influencing and being modified by the synoptic disturbances.

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