scholarly journals Análise da Relação entre a Precipitação Média do Reservatório Orós, Brasil - Ceará, e os índices PDO e AMO Através da Análise de Changepoints e Transformada de Ondeletas

2019 ◽  
Vol 34 (1) ◽  
pp. 139-149 ◽  
Author(s):  
Renan Vieira Rocha ◽  
Francisco de Assis de Souza Filho ◽  
Samiria Maria Oliveira da Silva
Keyword(s):  
Pacific Decadal Oscillation ◽  
Atlantic Multidecadal Oscillation

Resumo Os riscos de extremos hidrológicos para um local ou região estão associados aos modos de variação do clima, em suas diversas escalas temporais. A compreensão da variabilidade de baixa frequência ganha uma elevada importância em regiões onde eventos de seca são frequentes, por estar associada a longos períodos de secas consecutivas. O presente artigo analisou a relação entre a precipitação média da bacia a montante da estação fluviométrica de Iguatu, com os índices PDO e AMO (Pacific Decadal Oscillation e Atlantic Multidecadal Oscillation) através das metodologias de Análise de changepoint, Transformada de Ondeletas (TO), Transformada de Ondeletas Cruzadas (XTC) e Análise da Coerência das Ondeletas (WTC). Essa estação mensura as vazões afluente ao reservatório de Orós, um dos principais do Estado do Ceará (Brasil). A precipitação média da bacia foi obtida a partir de dados de pluviômetros. Os resultados permitiram estabelecer uma relação entre a precipitação da região e os índices PDO e AMO, indicando que um modelo baseado nos índices pode ter alguma capacidade preditiva do comportamento da precipitação local. Nota-se também que períodos com fases simultaneamente positivas (negativas) da PDO e da AMO resultam em um comportamento mais previsível das precipitações da região, com valores abaixo (acima) do normalmente esperado.

scholarly journals Estimation of the SST Response to Anthropogenic and External Forcing and Its Impact on the Atlantic Multidecadal Oscillation and the Pacific Decadal Oscillation

2017 ◽  
Vol 30 (24) ◽  
pp. 9871-9895 ◽  
Author(s):  
Claude Frankignoul ◽  
Guillaume Gastineau ◽  
Young-Oh Kwon
Keyword(s):  
Pacific Decadal Oscillation ◽  
Linear Trend ◽  
Volcanic Eruptions ◽  
Atlantic Multidecadal Oscillation ◽  
Ensemble Empirical Mode Decomposition ◽  
Meridional Overturning Circulation ◽  
External Forcing ◽  
Optimal Perturbation ◽  
Sst Variability ◽  
The Pacific

Two large ensembles (LEs) of historical climate simulations are used to compare how various statistical methods estimate the sea surface temperature (SST) changes due to anthropogenic and other external forcing, and how their removal affects the internally generated Atlantic multidecadal oscillation (AMO), Pacific decadal oscillation (PDO), and the SST footprint of the Atlantic meridional overturning circulation (AMOC). Removing the forced SST signal by subtracting the global mean SST (GM) or a linear regression on it (REGR) leads to large errors in the Pacific. Multidimensional ensemble empirical mode decomposition (MEEMD) and quadratic detrending only efficiently remove the forced SST signal in one LE, and cannot separate the short-term response to volcanic eruptions from natural SST variations. Removing a linear trend works poorly. Two methods based on linear inverse modeling (LIM), one where the leading LIM mode represents the forced signal and another using an optimal perturbation filter (LIMopt), perform consistently well. However, the first two LIM modes are sometimes needed to represent the forced signal, so the more robust LIMopt is recommended. In both LEs, the natural AMO variability seems largely driven by the AMOC in the subpolar North Atlantic, but not in the subtropics and tropics, and the scatter in the AMOC–AMO correlation is large between individual ensemble members. In three observational SST reconstructions for 1900–2015, linear and quadratic detrending, MEEMD, and GM yield somewhat different AMO behavior, and REGR yields smaller PDO amplitudes. Based on LIMopt, only about 30% of the AMO variability is internally generated, as opposed to more than 90% for the PDO. The natural SST variability contribution to global warming hiatus is discussed.

Climate-associated trends and variability in ichthyoplankton phenology from the longest continuous larval fish time series on the east coast of the United States

2020 ◽  
Vol 650 ◽  
pp. 269-287
Author(s):  
WC Thaxton ◽  
JC Taylor ◽  
RG Asch
Keyword(s):  
United States ◽  
Environmental Variability ◽  
Larval Fish ◽  
Interspecific Interactions ◽  
River Estuary ◽  
Atlantic Multidecadal Oscillation ◽  
The United States ◽  
Larval Survival ◽  
Ecological Communities ◽  
Northerly Wind

As the effects of climate change become more pronounced, variation in the direction and magnitude of shifts in species occurrence in space and time may disrupt interspecific interactions in ecological communities. In this study, we examined how the fall and winter ichthyoplankton community in the Newport River Estuary located inshore of Pamlico Sound in the southeastern United States has responded to environmental variability over the last 27 yr. We relate the timing of estuarine ingress of 10 larval fish species to changes in sea surface temperature (SST), the Atlantic Multidecadal Oscillation, the North Atlantic Oscillation, wind strength and phenology, and tidal height. We also examined whether any species exhibited trends in ingress phenology over the last 3 decades. Species varied in the magnitude of their responses to all of the environmental variables studied, but most shared a common direction of change. SST and northerly wind strength had the largest impact on estuarine ingress phenology, with most species ingressing earlier during warm years and delaying ingress during years with strong northerly winds. As SST warms in the coming decades, the average date of ingress of some species (Atlantic croaker Micropogonias undulatus, summer flounder Paralichthys dentatus, pinfish Lagodon rhomboides) is projected to advance on the order of weeks to months, assuming temperatures do not exceed a threshold at which species can no longer respond through changes in phenology. These shifts in ingress could affect larval survival and growth since environmental conditions in the estuarine and pelagic nursery habitats of fishes also vary seasonally.

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