scholarly journals Dynamic Characteristics of the Circulation and Diurnal Spatial Cycle of Outgoing Longwave Radiation in the Different Phases of the Madden–Julian Oscillation during the Formation of the South Atlantic Convergence Zone

Atmosphere ◽  
2021 ◽  
Vol 12 (11) ◽  
pp. 1399
Author(s):  
Liviany P. Viana ◽  
Jhonatan A. A. Manco ◽  
Dirceu Luis Herdies
Keyword(s):  
Outgoing Longwave Radiation ◽  
Longwave Radiation ◽  
Active Phase ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Meteorological Variables ◽  
Convergence Zone ◽  
Madden Julian Oscillation ◽  
The South ◽  
Subtropical Highs

In this work, we verified the formation of the South Atlantic Convergence Zone (SACZ) during the active, unfavorable, and transition phases of the Madden–Julian Oscillation (MJO), as well as the diurnal spatial variability in the estimated Outgoing Longwave Radiation (OLR) data. The real-time multivariate index (RMM) and the composites of meteorological variables were used, along with the temporal average of the estimated OLR data. All the different patterns for the average period of SACZ showed classic behavior: well-organized and with meteorological variables in phases throughout the troposphere. However, some differences were evident in the organization of each phase of the MJO: at 200 hPa, the Bolivian High (BH) was more flattened during the active phase pattern than in the unfavorable and transition phases, being wider and with a wavier trough embedded in the western flow; at medium levels, the subtropical highs appeared more defined and with a very wide trough; the trough supported the frontal systems on the surface and, together with the subtropical highs, concentrated all the moisture in this layer. In the OLR dataset, the formation of the Coast Squall Line (CSL) occurred during SACZ events in the active phase and MJO transition, whereas in the unfavorable phase, this system was not observed.

Natural Disasters in Southeastern Brazil Associated with the South Atlantic Convergence Zone

2017 ◽  
Author(s):  
Jonas Teixeira Nery ◽  
Leônidas Malvestio
Keyword(s):  
Natural Disasters ◽  
Outgoing Longwave Radiation ◽  
Longwave Radiation ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Southeastern Brazil ◽  
Convergence Zone ◽  
The South ◽  
Close Relationship ◽  
National Water

Abstract. This study analyzed rains in southeastern Brazil associated with the South Atlantic Convergence Zone (SACZ), which resulted in several disasters over the study area. The study period was from 1976 to 2010 and data were obtained from the National Water Agency (ANA) and Department of Water and Energy (DAEE) of the state of São Paulo. Outgoing Longwave Radiation (OLR) data were also used to analyze SACZ, which is an important dynamics influencing spring and summer in this region. A close relationship between SACZ intensity and economic and life losses in the study area was observed.

scholarly journals Connecting heavy precipitation events to outgoing longwave radiation variability scales: case analysis in Brazil

2021 ◽  
Author(s):  
Gabriela Viviana Müller ◽  
Valesca Fernandes
Keyword(s):  
Pacific Ocean ◽  
Outgoing Longwave Radiation ◽  
Longwave Radiation ◽  
South Pacific ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Southeastern Brazil ◽  
Convergence Zone ◽  
The South ◽  
Scale Interaction

Spatial fields of outgoing longwave radiation (OLR) spectrum variance are analyzed in different time-scales: synoptic, sub-monthly, intra-seasonal, during the 1979-2016 austral summer months in southern Brazil. Variability fields differ both in intensity and location and highlight dominant convection cycles in the study area. The results show that the amplitude of sub-monthly variability is greater than the other scales in the southeastern region of Brazil, while the synoptic scale prevails in the southern region. The above-mentioned scales show higher amplitudes over the western Pacific Ocean where the Madden-Julian Oscillation plays an important role, along the South Pacific Convergence Zone, and over the storm track areas over the South Pacific Ocean. The influence of spectral OLR scale interaction is also analyzed, associated to the occurrence of two intense rainfall events over the southeastern Brazil in the austral summers of 2011 and 2014 when the South Atlantic Convergence Zone was involved in both events. The results obtained suggest that spectral OLR scale interaction takes place in such way that it strengthens the South Atlantic Convergence Zone, since the spatial pattern footprints of the 2 to 8-day timescale (synoptic), 10 to 30-day timescale (sub-monthly) and 30 to 60-day timescale (intra-seasonal) overlap in the study region.

scholarly journals Isotopic Composition of Precipitation in a Southeastern Region of Brazil during the Action of the South Atlantic Convergence Zone

Atmosphere ◽  
2021 ◽  
Vol 12 (4) ◽  
pp. 418
Author(s):  
Cleber Santos ◽  
Rayonil Carneiro ◽  
Camilla Borges ◽  
Didier Gastmans ◽  
Laura Borma
Keyword(s):  
Isotopic Composition ◽  
Hydrological Cycle ◽  
Statistical Tests ◽  
Spatial Scales ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Southeastern Brazil ◽  
Convergence Zone ◽  
The South ◽  
Hysplit Model

The use of stable isotopes of hydrogen and oxygen is a tool widely used to trace water paths along the hydrological cycle, providing support for understanding climatic conditions in different spatial scales. One of the main synoptic scale events acting in southeastern Brazil is the South Atlantic Convergence Zone (SACZ), which causes a large amount of precipitation from southern Amazonia to southeastern Brazil during the southern summer. In order to determine the isotopic composition of precipitation during the action of SACZ in São Francisco Xavier in southeastern Brazil, information from the Weather Forecasting and Climate Studies Center of the National Institute for Space Research (CPTEC) was used regarding SACZ performance days, the retrograde trajectories of the HYSPLIT model, and images from the GOES-16 satellite, in addition to the non-parametric statistical tests by Spearman and Kruskal–Wallis. A high frequency of air mass trajectories from the Amazon to southeastern Brazil was observed when the SACZ was operating. During the SACZ events, the average isotopic composition of precipitation was more depleted, with a δ18O of −9.9‰ (±2.1‰), a δ2H of −69.3‰ (±17.9‰), and d-excess of 10.1‰ (±4.0‰). When disregarding the SACZ performance, the annual isotopic composition can present an enrichment of 1.0‰ for δ18O and 8.8‰ for the δ2H. The long-term monitoring of trends in the isotopic composition of precipitation during the SACZ events can assist in indicating the evapotranspiration contribution of the Amazon rainforest to the water supply of southeastern Brazil.

scholarly journals Dynamics-based regression models for the South Atlantic Convergence Zone

2018 ◽  
Vol 52 (9-10) ◽  
pp. 5527-5553
Author(s):  
David Marcolino Nielsen ◽  
André Luiz Belém ◽  
Edilson Marton ◽  
Marcio Cataldi
Keyword(s):  
Regression Models ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Convergence Zone ◽  
The South

scholarly journals Atmospheric convergence zones stemming from large-scale mixing

2021 ◽  
Vol 2 (2) ◽  
pp. 475-488
Author(s):  
Gabriel M. P. Perez ◽  
Pier Luigi Vidale ◽  
Nicholas P. Klingaman ◽  
Thomas C. M. Martin
Keyword(s):  
South America ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Moisture Flux ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Convergence Zone ◽  
The South ◽  
Atmospheric Flow ◽  
Convergence Zones

Abstract. Organised cloud bands are important features of tropical and subtropical rainfall. These structures are often regarded as convergence zones, alluding to an association with coherent atmospheric flow. However, the flow kinematics is not usually taken into account in classification methods for this type of event, as large-scale lines are rarely evident in instantaneous diagnostics such as Eulerian convergence. Instead, existing convergence zone definitions rely on heuristic rules of shape, duration and size of cloudiness fields. Here we investigate the role of large-scale turbulence in shaping atmospheric moisture in South America. We employ the finite-time Lyapunov exponent (FTLE), a metric of deformation among neighbouring trajectories, to define convergence zones as attracting Lagrangian coherent structures (LCSs). Attracting LCSs frequent tropical and subtropical South America, with climatologies consistent with the South Atlantic Convergence Zone (SACZ), the South American Low-Level Jet (SALLJ) and the Intertropical Convergence Zone (ITCZ). In regions under the direct influence of the ITCZ and the SACZ, rainfall is significantly positively correlated with large-scale mixing measured by the FTLE. Attracting LCSs in south and southeast Brazil are associated with significant positive rainfall and moisture flux anomalies. Geopotential height composites suggest that the occurrence of attracting LCSs in these regions is related with teleconnection mechanisms such as the Pacific–South Atlantic. We believe that this kinematical approach can be used as an alternative to region-specific convergence zone classification algorithms; it may help advance the understanding of underlying mechanisms of tropical and subtropical rain bands and their role in the hydrological cycle.

scholarly journals Atmospheric convergence zones stemming from large-scale mixing

2020 ◽  
Author(s):  
Gabriel M. P. Perez ◽  
Pier Luigi Vidale ◽  
Nicholas P. Klingaman ◽  
Thomas C. M. Martin
Keyword(s):  
South America ◽  
Large Scale ◽  
Hydrological Cycle ◽  
Moisture Flux ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Convergence Zone ◽  
The South ◽  
Atmospheric Flow ◽  
Convergence Zones

Abstract. Organised cloud bands are important features of tropical and subtropical rainfall. These structures are often regarded as convergence zones, alluding to an association with coherent atmospheric flow. However, the flow kinematics is not usually taken into account in classification methods for this type of event, as large-scale lines are rarely evident in instantaneous diagnostics such as Eulerian convergence. Instead, existing convergence zone definitions rely on heuristic rules of shape, duration and size of cloudiness fields. Here we investigate the role of large-scale turbulence in shaping atmospheric moisture in South America. We employ the Finite-Time Lyapunov Exponent (FTLE), a metric of deformation among neighboring trajectories, to define convergence zones as attracting Lagrangian Coherent Structures (LCSs). Attracting LCSs frequent tropical and subtropical South America, with climatologies consistent with the South Atlantic Convergence Zone (SACZ), the South American Low-level Jet (SALLJ) and the Intertropical Convergence Zone (ITCZ). In regions under the direct influence of the ITCZ and the SACZ, rainfall is significantly positively correlated with large-scale mixing measured by the FTLE. Attracting LCSs in South and Southeast Brazil are associated with significant positive rainfall and moisture flux anomalies. Geopotential height composites suggest that the occurrence of attracting LCSs in these regions is related with teleconnection mechanisms such as the Pacific-South Atlantic. We believe that this kinematical approach can be used as an alternative to region-specific convergence zone classification algorithms; it may help advance the understanding of underlying mechanisms of tropical and subtropical rain bands and their role in the hydrological cycle.

scholarly journals Submonthly Convective Variability over South America and the South Atlantic Convergence Zone

1999 ◽  
Vol 12 (7) ◽  
pp. 1877-1891 ◽  
Author(s):  
Brant Liebmann ◽  
George N. Kiladis ◽  
JoséA. Marengo ◽  
Tércio Ambrizzi ◽  
John D. Glick
Keyword(s):  
South America ◽  
South Atlantic Convergence Zone ◽  
South Atlantic ◽  
Convergence Zone ◽  
The South
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