Atmospheric Dynamic and Thermodynamic Processes Driving the Western North Pacific Anomalous Anticyclone during El Niño. Part I: Maintenance MechanismsSource: Journal of Climate:;2017:;volume( 030 ):;issue: 023::page 9621Author:Wu, Bo;Zhou, Tianjun;Li, Tim
DOI: 10.1175/JCLI-D-16-0489.1Publisher: American Meteorological Society
Abstract: AbstractThe western North Pacific anomalous anticyclone (WNPAC) is an important low-level circulation system that connects El Niño and the East Asian monsoon. In this study, the mechanisms responsible for the formation and maintenance of the WNPAC are explored. Part I of this study focuses on the WNPAC maintenance mechanisms during El Niño mature winter and the following spring. Moisture and moist static energy analyses indicated that the WNPAC is maintained by both the remote forcing from the equatorial central-eastern Pacific via the atmospheric bridge and the local air?sea interactions. Three pacemaker experiments by a coupled global climate model FGOALS-s2, with upper-700-m ocean temperature in the equatorial central-eastern Pacific restored to the observational anomalies plus model climatology, suggest that about 60% (70%) intensity of the WNPAC during the winter (spring) is contributed by the remote forcing from the equatorial central-eastern Pacific. The key remote forcing mechanism responsible for the maintenance of the WNPAC is revealed. In response to El Niño?related positive precipitation anomalies over the equatorial central-eastern Pacific, twin Rossby wave cyclonic anomalies are induced to the west. The northern branch of the twin cyclonic anomalies advects dry and low moist enthalpy air into the tropical western North Pacific, which suppresses local convection. The suppressed convection further drives the WNPAC.
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contributor author | Wu, Bo;Zhou, Tianjun;Li, Tim | |
date accessioned | 2018-01-03T11:00:45Z | |
date available | 2018-01-03T11:00:45Z | |
date copyright | 8/15/2017 12:00:00 AM | |
date issued | 2017 | |
identifier other | jcli-d-16-0489.1.pdf | |
identifier uri | http://138.201.223.254:8080/yetl1/handle/yetl/4246014 | |
description abstract | AbstractThe western North Pacific anomalous anticyclone (WNPAC) is an important low-level circulation system that connects El Niño and the East Asian monsoon. In this study, the mechanisms responsible for the formation and maintenance of the WNPAC are explored. Part I of this study focuses on the WNPAC maintenance mechanisms during El Niño mature winter and the following spring. Moisture and moist static energy analyses indicated that the WNPAC is maintained by both the remote forcing from the equatorial central-eastern Pacific via the atmospheric bridge and the local air?sea interactions. Three pacemaker experiments by a coupled global climate model FGOALS-s2, with upper-700-m ocean temperature in the equatorial central-eastern Pacific restored to the observational anomalies plus model climatology, suggest that about 60% (70%) intensity of the WNPAC during the winter (spring) is contributed by the remote forcing from the equatorial central-eastern Pacific. The key remote forcing mechanism responsible for the maintenance of the WNPAC is revealed. In response to El Niño?related positive precipitation anomalies over the equatorial central-eastern Pacific, twin Rossby wave cyclonic anomalies are induced to the west. The northern branch of the twin cyclonic anomalies advects dry and low moist enthalpy air into the tropical western North Pacific, which suppresses local convection. The suppressed convection further drives the WNPAC. | |
publisher | American Meteorological Society | |
title | Atmospheric Dynamic and Thermodynamic Processes Driving the Western North Pacific Anomalous Anticyclone during El Niño. Part I: Maintenance Mechanisms | |
type | Journal Paper | |
journal volume | 30 | |
journal issue | 23 | |
journal title | Journal of Climate | |
identifier doi | 10.1175/JCLI-D-16-0489.1 | |
journal fristpage | 9621 | |
journal lastpage | 9635 | |
tree | Journal of Climate:;2017:;volume( 030 ):;issue: 023 | |
contenttype | Fulltext |