Efeitos do gradiente de TSM zonal entre as bacias do Pacífico e Atlântico no norte da América do Sul durante eventos ENOS
The impacts of anomalous events in the Pacific Ocean associated with the El Niño-Southern Oscillation (ENSO) on the Amazon precipitation were evaluated using observational analyses and numerical simulations. The ENSO events which develop subsequent to an anomalous condition with opposite sign in the...
| Autor principal: | Gonzalez, Rosimeire Araújo |
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| Grau: | Dissertação |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
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| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/12600 http://buscatextual.cnpq.br/buscatextual/visualizacv.do?id=K4220054U3 |
| Resumo: |
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The impacts of anomalous events in the Pacific Ocean associated with the El Niño-Southern Oscillation (ENSO) on the Amazon precipitation were evaluated using observational analyses and numerical simulations. The ENSO events which develop subsequent to an anomalous condition with opposite sign in the Sea Surface Temperature (SST) in the Equatorial Atlantic (inter-Pacific-Atlantic gradient) and those events which develop during normal conditions in the Tropical Atlantic (TA) were considered separately. The observational results suggest that ENSO affects the precipitation regime in the Northern region of South America in different ways, depending on the precondition of the Equatorial Atlantic. During December February (DJF), for events following an anomalous condition in TA, an intensification of precipitation anomalies was observed, mainly in the Northeastern and Central-Eastern Amazon; whereas for ENSO events under normal TA conditions, the anomalies are more significant in the Northern and Western region of the basin. Thus, during DJF the mature phase of ENSO events the Central-Eastern and Northeastern South America seem to suffer a combined effect of the Pacific and the Atlantic oceans, whereas the variability in precipitation in the Northern and Western regions is related only to the Pacific SST variations. On the other hand, during March May (MAM) and June August (JJA), both the Pacific and the Atlantic oceans appear to modulate the precipitation variability. Consistent with the observational analyses, the simulation results indicate a strengthening of precipitation anomalies under the occurrence of the inter-basin gradient in the initial phase of the development of these events, associated with the strengthening of anomalous Walker and Hadley cells. This is possibly associated with the establishment of inter-basin gradients in the mature phase of the anomalous Pacific events, and with the inter-hemispheric gradient observed in the TA. The horizontal circulation anomalous patterns causing part of the humidity transportation to Northern South America were also analyzed. The analyses of wind fields at upper and low levels indicate differences in the tropical-extratropical circulations associated with changes in the anomalous behavior of SST in regions of the Pacific and the Atlantic, which affect the transportation of humidity on the continent and modulate the intensity of the rains in the entire region under study. Consistent with previous studies, the results here demonstrate that not all El Niños necessarily produce canonical impacts, due to the combined action of the Equatorial Pacific and the TA in modulating the regional circulation cells. This indicates the importance of our knowledgement of the TA pre-condition during the development phase of the ENSO events in order to improve climate forecasts for the Northern region of South America. |