On the Inconsistent Relationship between Pacific and Atlantic NiñosSource: Journal of Climate:;2012:;volume( 025 ):;issue: 012::page 4294DOI: 10.1175/JCLI-D-11-00553.1Publisher: American Meteorological Society
Abstract: he tropical Atlantic wind response to El Niño forcing is robust, with weakened northeast trade winds north of the equator and strengthened southeast trade winds along and south of the equator. However, the relationship between sea surface temperature (SST) anomalies in the eastern equatorial Pacific and Atlantic is inconsistent, with El Niño events followed sometimes by warm and other times by cold boreal summer anomalies in the Atlantic cold tongue region. Using observational data and a hindcast simulation of the Nucleus for European Modeling of the Ocean (NEMO) global model at 0.5° resolution (NEMO-ORCA05), this inconsistent SST relationship is shown to be at least partly attributable to a delayed negative feedback in the tropical Atlantic that is active in years with a warm or neutral response in the eastern equatorial Atlantic. In these years, the boreal spring warming in the northern tropical Atlantic that is a typical response to El Niño is pronounced, setting up a strong meridional SST gradient. This leads to a negative wind stress curl anomaly to the north of the equator that generates downwelling Rossby waves. When these waves reach the western boundary, they are reflected into downwelling equatorial Kelvin waves that reach the cold tongue region in late boreal summer to counteract the initial cooling that is due to the boreal winter wind stress response to El Niño. In contrast, this initial cooling persists or is amplified in years in which the boreal spring northern tropical Atlantic warming is weak or absent either because of a positive North Atlantic Oscillation (NAO) phase or an early termination of the Pacific El Niño event.
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contributor author | Lübbecke, Joke F. | |
contributor author | McPhaden, Michael J. | |
date accessioned | 2017-06-09T17:05:19Z | |
date available | 2017-06-09T17:05:19Z | |
date copyright | 2012/06/01 | |
date issued | 2012 | |
identifier issn | 0894-8755 | |
identifier other | ams-79201.pdf | |
identifier uri | http://onlinelibrary.yabesh.ir/handle/yetl/4221954 | |
description abstract | he tropical Atlantic wind response to El Niño forcing is robust, with weakened northeast trade winds north of the equator and strengthened southeast trade winds along and south of the equator. However, the relationship between sea surface temperature (SST) anomalies in the eastern equatorial Pacific and Atlantic is inconsistent, with El Niño events followed sometimes by warm and other times by cold boreal summer anomalies in the Atlantic cold tongue region. Using observational data and a hindcast simulation of the Nucleus for European Modeling of the Ocean (NEMO) global model at 0.5° resolution (NEMO-ORCA05), this inconsistent SST relationship is shown to be at least partly attributable to a delayed negative feedback in the tropical Atlantic that is active in years with a warm or neutral response in the eastern equatorial Atlantic. In these years, the boreal spring warming in the northern tropical Atlantic that is a typical response to El Niño is pronounced, setting up a strong meridional SST gradient. This leads to a negative wind stress curl anomaly to the north of the equator that generates downwelling Rossby waves. When these waves reach the western boundary, they are reflected into downwelling equatorial Kelvin waves that reach the cold tongue region in late boreal summer to counteract the initial cooling that is due to the boreal winter wind stress response to El Niño. In contrast, this initial cooling persists or is amplified in years in which the boreal spring northern tropical Atlantic warming is weak or absent either because of a positive North Atlantic Oscillation (NAO) phase or an early termination of the Pacific El Niño event. | |
publisher | American Meteorological Society | |
title | On the Inconsistent Relationship between Pacific and Atlantic Niños | |
type | Journal Paper | |
journal volume | 25 | |
journal issue | 12 | |
journal title | Journal of Climate | |
identifier doi | 10.1175/JCLI-D-11-00553.1 | |
journal fristpage | 4294 | |
journal lastpage | 4303 | |
tree | Journal of Climate:;2012:;volume( 025 ):;issue: 012 | |
contenttype | Fulltext |