The equilibrium response to idealized thermal forcings in a comprehensive GCM: implications for recent tropical expansion Allen, RJ en_US Sherwood, Steven en_US Norris, JR en_US Zender, CS en_US 2021-11-25T12:30:29Z 2021-11-25T12:30:29Z 2012 en_US
dc.description.abstract Several recent studies have shown the width of the tropical belt has increased over the last several decades. The mechanisms driving tropical expansion are not well known and the recent expansion is underpredicted by state-of-the art GCMs. We use the CAM3 GCM to investigate how tropical width responds to idealized atmospheric heat sources, focusing on zonal displacement of the tropospheric jets. The heat sources include global and zonally restricted lower-tropospheric warmings and stratospheric coolings, which coarsely represent possible impacts of ozone or aerosol changes. Similar to prior studies with simplified GCMs, we find that stratospheric cooling - particularly at high-latitudes - shifts jets poleward and excites Northern and Southern Annular Mode (NAM/SAM)-type responses. We also find, however, that modest heating of the midlatitude boundary layer drives a similar response; heating at high latitudes provokes a weaker, equatorward shift and tropical heating produces no shift. Over 70 % of the variance in annual mean jet displacements across 27 experiments is accounted for by a newly proposed 'Expansion Index', which compares mid-latitude tropospheric warming to that at other latitudes. We find that previously proposed factors, including tropopause height and tropospheric stability, do not fully explain the results. Results suggest recently observed tropical expansion could have been driven not only by stratospheric cooling, but also by mid-latitude heating sources due for example to ozone or aerosol changes. en_US
dc.identifier.issn 1680-7316 en_US
dc.language English
dc.language.iso EN en_US
dc.rights CC BY-NC-ND 3.0 en_US
dc.rights.uri en_US
dc.source Legacy MARC en_US
dc.title The equilibrium response to idealized thermal forcings in a comprehensive GCM: implications for recent tropical expansion en_US
dc.type Journal Article en
dcterms.accessRights open access
dspace.entity.type Publication en_US
unsw.identifier.doiPublisher en_US
unsw.relation.FunderRefNo NA10OAR43210141 en_US
unsw.relation.FunderRefNo ARC-0714088
unsw.relation.FunderRefNo NNX07AR23G
unsw.relation.faculty Science
unsw.relation.fundingScheme SIO NOAA, NSF, NASA, UC Irvbine en_US
unsw.relation.ispartofissue 10 en_US
unsw.relation.ispartofjournal Atmospheric Chemistry and Physics en_US
unsw.relation.ispartofpagefrompageto 4795-4816 en_US
unsw.relation.ispartofvolume 12 en_US
unsw.relation.originalPublicationAffiliation Allen, RJ en_US
unsw.relation.originalPublicationAffiliation Sherwood, Steven, Climate Change Research Centre (CCRC), Faculty of Science, UNSW en_US
unsw.relation.originalPublicationAffiliation Norris, JR en_US
unsw.relation.originalPublicationAffiliation Zender, CS en_US School of Biological, Earth & Environmental Sciences *
Original bundle
Now showing 1 - 1 of 1
Thumbnail Image
Publisher's version.pdf
1.67 MB
Resource type