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The Aqua-Planet Experiment (APE): Response to Changed Meridional SST Profile

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Title: The Aqua-Planet Experiment (APE): Response to Changed Meridional SST Profile
Authors: Williamson, David L. Browse this author
Blackburn, Michael Browse this author
Nakajima, Kensuke Browse this author →KAKEN DB
Ohfuchi, Wataru Browse this author →KAKEN DB
Takahashi, Yoshiyuki O. Browse this author →KAKEN DB
Hayashi, Yoshi-Yuki Browse this author
Nakamura, Hisashi Browse this author →KAKEN DB
Ishiwatari, Masaki Browse this author →KAKEN DB
Mcgregor, John L. Browse this author
Borth, Hartmut Browse this author
Wirth, Volkmar Browse this author
Keywords: comparison of atmospheric general circulation models (GCMs)
sea surface temperature profile
Hadley circulation
intertropical convergence zone (ITCZ)
Issue Date: Sep-2013
Publisher: Meteorological soc japan
Journal Title: Journal of the meteorological society of japan
Volume: 91A
Start Page: 57
End Page: 89
Publisher DOI: 10.2151/jmsj.2013-A03
Abstract: This paper explores the sensitivity of Atmospheric General Circulation Model (AGCM) simulations to changes in the meridional distribution of sea surface temperature (SST). The simulations are for an aqua-planet, a water covered Earth with no land, orography or sea-ice and with specified zonally symmetric SST. Simulations from 14 AGCMs developed for Numerical Weather Prediction and climate applications are compared. Four experiments are performed to study the sensitivity to the meridional SST profile. These profiles range from one in which the SST gradient continues to the equator to one which is flat approaching the equator, all with the same maximum SST at the equator. The zonal mean circulation of all models shows strong sensitivity to latitudinal distribution of SST. The Hadley circulation weakens and shifts poleward as the SST profile flattens in the tropics. One question of interest is the formation of a double versus a single ITCZ. There is a large variation between models of the strength of the ITCZ and where in the SST experiment sequence they transition from a single to double ITCZ. The SST profiles are defined such that as the equatorial SST gradient flattens, the maximum gradient increases and moves poleward. This leads to a weakening of the mid-latitude jet accompanied by a poleward shift of the jet core. Also considered are tropical wave activity and tropical precipitation frequency distributions. The details of each vary greatly between models, both with a given SST and in the response to the change in SST. One additional experiment is included to examine the sensitivity to an off-equatorial SST maximum. The upward branch of the Hadley circulation follows the SST maximum off the equator. The models that form a single precipitation maximum when the maximum SST is on the equator shift the precipitation maximum off equator and keep it centered over the SST maximum. Those that form a double with minimum on the equatorial maximum SST shift the double structure off the equator, keeping the minimum over the maximum SST. In both situations only modest changes appear in the shifted profile of zonal average precipitation. When the upward branch of the Hadley circulation moves into the hemisphere with SST maximum, the zonal average zonal, meridional and vertical winds all indicate that the Hadley cell in the other hemisphere dominates.
Type: article
Appears in Collections:理学院・理学研究院 (Graduate School of Science / Faculty of Science) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 石渡 正樹

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