A variabilidade da precipitação sobre a América do Sul tropi- cal associada a oscilações interanual e intrasazonal.
Intra-seasonal and inter-annual oscillations are responsible for part of precipitation ex- tremes during austral summer. In view of this, this study aimed to analyze the intra- seasonal variability modes on time scales of 8-24 days and 30-90 days associated with extreme events of daily precipitat...
| Autor principal: | LIMA, Alexandra Amaro de |
|---|---|
| Grau: | Tese |
| Idioma: | por |
| Publicado em: |
Instituto Nacional de Pesquisas da Amazônia - INPA
2020
|
| Assuntos: | |
| Acesso em linha: |
https://repositorio.inpa.gov.br/handle/1/12959 http://lattes.cnpq.br/6915958689972413 |
| Resumo: |
|---|
|
Intra-seasonal and inter-annual oscillations are responsible for part of precipitation ex-
tremes during austral summer. In view of this, this study aimed to analyze the intra-
seasonal variability modes on time scales of 8-24 days and 30-90 days associated with
extreme events of daily precipitation over South America for 14 summer seasons, from
1998 to 2012. To achieve this we used a set of daily rainfall data from TRMM (Tropical
Rainfaill Measuring Mission -NASA), stream functions and moisture fluxes obtained by
NCEP Reanalysis - 2 (National Center for Environmental Prediction), with analysis of
orthogonal functions, which made possible finding the three dominant modes on South
America, and the Morlet wavelet transform to check for variations in the scales of 8-
24 and 30-90 days. Composite analyzes were used to assess the possible relation
between the variability modes, when they operate separately and simultaneously. In
parallel, we investigated possible interactions between intra-seasonal events on scales
of 8-24 days during El Niño, La Nina and neutral years. The results indicated the domi-
nance of intra-seasonal scales of 8-24 days on the continent compared to 30-90 days
scale, especially when the events are in phase. The events operating in different pha-
ses showed a weakening of the precipitation anomalies on scales 8-24 (positive) and
30-90 (negative) and when reversing the signs we note a disorganization of convection.
The same is true during ENSO years. At the same time, it was found that during ENSO
years the intra-seasonal scale is enhanced by the joint action of the extra-tropical and
tropical wave-trains, and to the east of South America there is a predominance of intra-
seasonal systems, while in the west rainfall anomalies are dominated by inter-annual
variability. |