Interdiurnal Surface Pressure Variations in Brazil: Their Spatial Distributions, Origins and Effects

Kousky, Vernon E.; Ferreira, Nelson Jesus

doi:10.1175/1520-0493(1981)109<1999:ispvib>2.0.co;2

Cited by 26 publications

(40 citation statements)

References 0 publications

Supporting

Mentioning

Contrasting

Unclassified

Order By: Relevance

“…1g and j (moisture and temperature, respectively). These synoptic patterns have been previously identified by Kousky (1979) and Kousky and Ferreira (1981) as present both in winter and summer.…”

Section: Characterization Of Sams and Saczsupporting

confidence: 71%

Moisture transport and intraseasonal variability in the South America monsoon system

et al. 2010

View full text Add to dashboard Cite

This paper examines moisture transport on intraseasonal timescales over the continent and over the South Atlantic convergence zone (SACZ) during the South America (SA) summer monsoon. Combined Empirical Orthogonal Function analysis (EOFc) of Global Precipitation Climatology Project pentad precipitation, specific humidity, air temperature, zonal and meridional winds at 850 hPa (NCEP/NCAR reanalysis) are performed to identify the large-scale variability of the South America monsoon system and the SACZ. The first EOFc was used as a large-scale index for the South American monsoon (LISAM), whereas the second EOFc characterized the SACZ. LISAM (SACZ) index showed spectral variance on 30-90 (15-20) days and were both band filtered (10-100 days). Intraseasonal wet anomalies were defined when LISAM and SACZ anomalies were above the 75th percentile of their respective distribution. LISAM and SACZ wet events were examined independently of each other and when they occur simultaneously. LISAM wet events were observed with the amplification of wave activity in the Northern Hemisphere and the enhancement of northwesterly cross-equatorial moisture transport over tropical continental SA. Enhanced SACZ was observed with moisture transport from the extratropics of the Southern Hemisphere. Simultaneous LISAM and SACZ wet events are associated with cross-equatorial moisture transport along with moisture transport from Subtropical Southwestern Atlantic.

show abstract

Section: Characterization Of Sams and Saczsupporting

confidence: 71%

Moisture transport and intraseasonal variability in the South America monsoon system

et al. 2010

View full text Add to dashboard Cite

show abstract

“…For instance, during austral autumn, the Northeast Brazil is affected by the southward migration of the ITCZ that determines the rainy season in the region (Hastenrath, 1991). During the winter season, the South American precipitation is influenced by frontal systems, which are one of the most common synoptic events over the continent (Kousky, 1979;Kousky and Ferreira, 1981). These systems flow northward into the continent, causing intense drop in temperature and strong meridional winds.…”

Section: Introductionmentioning

confidence: 99%

“…In some cases, the cold air incursions can reach all the way into the Amazon Basin (Kousky, 1979(Kousky, , 1980. Kousky and Ferreira (1981) have reported the penetration of frontal systems into the Amazon and their role in modulating the rainfall in the region.…”

Section: Introductionmentioning

confidence: 99%

The impact of the subtropical South Atlantic SST on South American precipitation

Taschetto

Wainer

2008

Ann. Geophys.

View full text Add to dashboard Cite

Abstract. The Community Climate Model (CCM3) from the National Center for Atmospheric Research (NCAR) is used to investigate the effect of the South Atlantic sea surface temperature (SST) anomalies on interannual to decadal variability of South American precipitation. Two ensembles composed of multidecadal simulations forced with monthly SST data from the Hadley Centre for the period 1949 to 2001 are analysed.A statistical treatment based on signal-to-noise ratio and Empirical Orthogonal Functions (EOF) is applied to the ensembles in order to reduce the internal variability among the integrations. The ensemble treatment shows a spatial and temporal dependence of reproducibility. High degree of reproducibility is found in the tropics while the extratropics is apparently less reproducible. Austral autumn (MAM) and spring (SON) precipitation appears to be more reproducible over the South America-South Atlantic region than the summer (DJF) and winter (JJA) rainfall. While the Inter-tropical Convergence Zone (ITCZ) region is dominated by external variance, the South Atlantic Convergence Zone (SACZ) over South America is predominantly determined by internal variance, which makes it a difficult phenomenon to predict. Alternatively, the SACZ over western South Atlantic appears to be more sensitive to the subtropical SST anomalies than over the continent.An attempt is made to separate the atmospheric response forced by the South Atlantic SST anomalies from that associated with the El Niño -Southern Oscillation (ENSO). Results show that both the South Atlantic and Pacific SSTs modulate the intensity and position of the SACZ during DJF. Particularly, the subtropical South Atlantic SSTs are more important than ENSO in determining the position of the SACZ over the southeast Brazilian coast during DJF. On the other hand, the ENSO signal seems to influence the intensity of the SACZ not only in DJF but especially its oceanic Correspondence to: A. S. Taschetto (a.taschetto@unsw.edu.au) branch during MAM. Both local and remote influences, however, are confounded by the large internal variance in the region. During MAM and JJA, the South Atlantic SST anomalies affect the magnitude and the meridional displacement of the ITCZ. In JJA, the ENSO has relatively little influence on the interannual variability of the simulated rainfall. During SON, however, the ENSO seems to counteract the effect of the subtropical South Atlantic SST variations on convection over South America.

show abstract

“…Este, comparando com a Figura 4B, indica uma divisão do seu centro, no que podemos dizer que o centro mais ao sul seria a BNOA enquanto que o mais ao norte, sobre a Bolívia, seria a Baixa do Chaco. É comum, especialmente nesta época do ano, a conjunção entre o sistema frontal e a baixa continental, formando uma zona de nebulosidade no sentido noroeste-sudeste (Kousky & Ferreira, 1981;Garreaud & Wallace, 1998). Também neste dia iniciou-se uma ciclogênese extratropical em superfície, aproximadamente em 45°S, que intensificou-se no dia seguinte (Figura 4D), à sotavento do cavado (ou VCAN), conforme indica a literatura (Palmén & Newton, 1969, entre outros).…”

Section: Estudo De Caso De Sistemas Meteorológicos Em Altos Níveis Sounclassified

Case Study of Upper Tropospheric Meteorological Systems on South America: Synoptic Analysis

Nunes

2017

Anuário IGEO UFRJ

View full text Add to dashboard Cite

ResumoO Vórtice ciclônico de altos níveis (VCAN) sobre o nordeste brasileiro (NeB) e a Alta da Bolívia (AB) são os típicos sistemas de pressão em altos níveis (250 hPa) da América do Sul, especialmente nas estações mais quentes. Somados a eles, também pode-se considerar o VCAN extratropical, de característica transiente e encontrado o ano todo. Neste trabalho, é apresentada uma análise sinótica, baseada na literatura especializada, de um caso observado em 01 de fevereiro de 2005 em que os três sistemas ocorreram simultaneamente. Algumas características encontradas na literatura foram observadas nos sistemas deste caso. O campo de temperatura mais associado ao sistema extratropical foi o de 500 hPa, e não o de 250 hPa. Os movimentos verticais mais relevantes foram encontrados somente no sistema extratropical: intensos movimentos ascendentes à sotavento do eixo do cavado em altos níveis. Não se encontrou um sistema em superfície especificamente associado ao VCAN do NeB, enquanto que se observou a baixa continental (ou Baixa do Chaco) associada à Alta da Bolívia e um intenso ciclone extratropical associado ao VCAN extratropical. Tal ciclone em superfície acarretou em vento sul e consequente resfriamento da camada, o que pôde ser observado pela amplitude do cavado em altos níveis, o que é raro para esta época do ano. Palavras-chave: vórtices ciclônicos de altos níveis; Alta da Bolívia; vento térmico; Palmén; Palmer AbstractThe upper tropospheric cyclonic vortex (VCAN) over northeastern Brazil (NeB) and the Bolivian High (AB) are the South America typical upper level (250 hPa) pressure systems, especially in warmer seasons. Besides these, one can also consider the extratropical VCAN, which has transient feature and is found throughout the year. In this work is presented a synoptic analysis, based on the specialized literature, of a case observed in February 01, 2005, when the three systems occurred simultaneously. Some features found in literature were noted in the systems of this case. The temperature field most associated to the extratropical system was 500 hPa and not 250 hPa. The most significant vertical movements were only found in extratropical system: intense upward movements in the lee of the upper tropospheric trough axis. It has found no system specifically associated to VCAN of NeB, while it was observed the association between the continental low (or Chaco Low) and the Bolivian High and an intense extratropical cyclone associated to extratropical VCAN. Such surface cyclone carries on a southerly and consequent cooling of the layer, what could be observed by the amplitude of the upper tropospheric trough, which is unusual in this season.

show abstract

Interdiurnal Surface Pressure Variations in Brazil: Their Spatial Distributions, Origins and Effects

Cited by 26 publications

References 0 publications

Moisture transport and intraseasonal variability in the South America monsoon system

Moisture transport and intraseasonal variability in the South America monsoon system

The impact of the subtropical South Atlantic SST on South American precipitation

Case Study of Upper Tropospheric Meteorological Systems on South America: Synoptic Analysis

Contact Info

Product

Resources

About