Multiscale Dynamical Processes Underlying the Wintertime Atlantic BlockingsSource: Journal of the Atmospheric Sciences:;2017:;Volume( 074 ):;issue: 011::page 3815Author:Ma, Jiwang;San Liang, X.
DOI: 10.1175/JAS-D-16-0295.1Publisher: American Meteorological Society
Abstract: AbstractThe wintertime atmospheric blocking over the Atlantic is investigated using a newly developed methodology?namely, localized multiscale energy and vorticity analysis (MS-EVA)?and the theory of canonical energy transfer. Through a multiscale window transform (MWT), the atmospheric fields from the ERA-40 data are reconstructed on three-scale ranges or scale windows: basic-flow window, blocking window, and synoptic window. The blocking event is obtained by compositing the wintertime blocking episodes, and a clear westward-retrograding signal is identified on the blocking window. Likewise, the local multiscale energetics following the signal are composited. It is found that a life cycle of the blocking-scale kinetic energy (KE) may be divided into three phases: onset phase, amplification phase, and decay phase. Different phases have different mechanisms in play. In general, pressure work and the canonical transfer from the synoptic eddies initiate the generation of the blocking, while the latter contributes to its amplification. The blocking decays as the system transports the KE away and as it converts the KE into available potential energy (APE) through buoyancy conversion. For the APE on the blocking window, its evolution experiences two maxima and, correspondingly, two phases can be distinguished. In the first maximum phase, the dominating mechanism is baroclinic instability; in the second, buoyancy conversion takes place. These are also the mechanisms that cause the warm core of the blocking in the troposphere.
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contributor author | Ma, Jiwang;San Liang, X. | |
date accessioned | 2018-01-03T11:02:31Z | |
date available | 2018-01-03T11:02:31Z | |
date copyright | 7/26/2017 12:00:00 AM | |
date issued | 2017 | |
identifier other | jas-d-16-0295.1.pdf | |
identifier uri | http://138.201.223.254:8080/yetl1/handle/yetl/4246456 | |
description abstract | AbstractThe wintertime atmospheric blocking over the Atlantic is investigated using a newly developed methodology?namely, localized multiscale energy and vorticity analysis (MS-EVA)?and the theory of canonical energy transfer. Through a multiscale window transform (MWT), the atmospheric fields from the ERA-40 data are reconstructed on three-scale ranges or scale windows: basic-flow window, blocking window, and synoptic window. The blocking event is obtained by compositing the wintertime blocking episodes, and a clear westward-retrograding signal is identified on the blocking window. Likewise, the local multiscale energetics following the signal are composited. It is found that a life cycle of the blocking-scale kinetic energy (KE) may be divided into three phases: onset phase, amplification phase, and decay phase. Different phases have different mechanisms in play. In general, pressure work and the canonical transfer from the synoptic eddies initiate the generation of the blocking, while the latter contributes to its amplification. The blocking decays as the system transports the KE away and as it converts the KE into available potential energy (APE) through buoyancy conversion. For the APE on the blocking window, its evolution experiences two maxima and, correspondingly, two phases can be distinguished. In the first maximum phase, the dominating mechanism is baroclinic instability; in the second, buoyancy conversion takes place. These are also the mechanisms that cause the warm core of the blocking in the troposphere. | |
publisher | American Meteorological Society | |
title | Multiscale Dynamical Processes Underlying the Wintertime Atlantic Blockings | |
type | Journal Paper | |
journal volume | 74 | |
journal issue | 11 | |
journal title | Journal of the Atmospheric Sciences | |
identifier doi | 10.1175/JAS-D-16-0295.1 | |
journal fristpage | 3815 | |
journal lastpage | 3831 | |
tree | Journal of the Atmospheric Sciences:;2017:;Volume( 074 ):;issue: 011 | |
contenttype | Fulltext |