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A "cold path" for Gulf Stream - troposphere connection

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Title: A "cold path" for Gulf Stream - troposphere connection
Authors: Czaja, A
Vanniere, B
Dacre, H
Item Type: Journal Article
Abstract: The mechanism by which the Gulf Stream sea surface temperature (SST) front anchors a band of precipitation on its warm edge is still a matter of debate and little is known about how synoptic activity contributes to the mean state. In the present study, the influence of the SST front on precipitation is investigated during the course of a single extratropical cyclone using a regional configuration of the Met Office Unified Model. The comparison of a control run with a simulation in which SST gradients were smoothed brought the following conclusions: a band of precipitation is reproduced for a single extratropical cyclone and the response to the SST gradient is dominated by a change of convective precipitation in the cold sector of the storm. Several climatological features described by previous studies, such as surface wind convergence on the warm edge or a meridional circulation cell across the SST front, are also reproduced at synoptic time scales in the cold sector. Based on these results, a simple boundary layer model is proposed to explain the convective and dynamical response to the SST gradient in the cold sector. In this model, cold and dry air parcels acquire more buoyancy over a sharp SST gradient and become more convectively unstable. The convection sets a pressure anomaly over the entire depth of the boundary layer which drives wind convergence. This case study offers a new pathway by which the SST gradient can anchor a climatological band of precipitation.
Issue Date: 2-Feb-2017
Date of Acceptance: 4-Nov-2016
URI: http://hdl.handle.net/10044/1/42486
DOI: https://dx.doi.org/10.1175/JCLI-D-15-0749.1
ISSN: 1520-0442
Publisher: American Meteorological Society
Start Page: 1363
End Page: 1379
Journal / Book Title: Journal of Climate
Volume: 30
Copyright Statement: © 2017 American Meteorological Society. This article is licensed under a Creative Commons Attribution 4.0 license (http://creativecommons.org/licenses/by/4.0/).
Sponsor/Funder: Natural Environment Research Council (NERC)
Funder's Grant Number: NE/J023760/1
Keywords: Meteorology & Atmospheric Sciences
0401 Atmospheric Sciences
0405 Oceanography
Publication Status: Published
Appears in Collections:Space and Atmospheric Physics
Centre for Environmental Policy
Faculty of Natural Sciences