The University of Southampton
University of Southampton Institutional Repository

Impact of resolving the diurnal cycle in an ocean–atmosphere GCM. Part 1: a diurnally forced OGCM

Impact of resolving the diurnal cycle in an ocean–atmosphere GCM. Part 1: a diurnally forced OGCM
Impact of resolving the diurnal cycle in an ocean–atmosphere GCM. Part 1: a diurnally forced OGCM
The diurnal cycle is a fundamental time scale in the climate system, at which the upper ocean and atmosphere are routinely observed to vary. Current climate models, however, are not configured to resolve the diurnal cycle in the upper ocean or the interaction of the ocean and atmosphere on these time scales. This study examines the diurnal cycle of the tropical upper ocean and its climate impacts. In the present paper, the first of two, a high vertical resolution ocean general circulation model (OGCM), with modified physics, is developed which is able to resolve the diurnal cycle of sea surface temperature (SST) and current variability in the upper ocean. It is then validated against a satellite derived parameterization of diurnal SST variability and in-situ current observations. The model is then used to assess rectification of the intraseasonal SST response to the Madden–Julian oscillation (MJO) by the diurnal cycle of SST. Across the equatorial Indo-Pacific it is found that the diurnal cycle increases the intraseasonal SST response to the MJO by around 20%. In the Pacific, the diurnal cycle also modifies the exchange of momentum between equatorially divergent Ekman currents and the meridionally convergent geostrophic currents beneath, resulting in a 10% increase in the strength of the Ekman cells and equatorial upwelling. How the thermodynamic and dynamical impacts of the diurnal cycle effect the mean state, and variability, of the climate system cannot be fully investigated in the constrained design of ocean-only experiments presented here. The second part of this study, published separately, addresses the climate impacts of the diurnal cycle in the coupled system by coupling the OGCM developed here to an atmosphere general circulation model.
0930-7575
575-590
Bernie, D.J.
48ce2ca0-8eb5-480d-9eb4-0c8b3506178a
Guilyardi, E.
d8e3cd51-7353-401c-994a-7bee46dc4b6b
Madec, G.
7e2ec04b-896a-4861-b2d0-b74f39d748c2
Slingo, J.M.
2e390b0a-d76e-4896-8234-3b24aeac0512
Woolnough, S.J.
80ef891d-d64b-4048-808a-1b2152f2c36d
Bernie, D.J.
48ce2ca0-8eb5-480d-9eb4-0c8b3506178a
Guilyardi, E.
d8e3cd51-7353-401c-994a-7bee46dc4b6b
Madec, G.
7e2ec04b-896a-4861-b2d0-b74f39d748c2
Slingo, J.M.
2e390b0a-d76e-4896-8234-3b24aeac0512
Woolnough, S.J.
80ef891d-d64b-4048-808a-1b2152f2c36d

Bernie, D.J., Guilyardi, E., Madec, G., Slingo, J.M. and Woolnough, S.J. (2007) Impact of resolving the diurnal cycle in an ocean–atmosphere GCM. Part 1: a diurnally forced OGCM. Climate Dynamics, 29 (6), 575-590. (doi:10.1007/s00382-007-0249-6).

Record type: Article

Abstract

The diurnal cycle is a fundamental time scale in the climate system, at which the upper ocean and atmosphere are routinely observed to vary. Current climate models, however, are not configured to resolve the diurnal cycle in the upper ocean or the interaction of the ocean and atmosphere on these time scales. This study examines the diurnal cycle of the tropical upper ocean and its climate impacts. In the present paper, the first of two, a high vertical resolution ocean general circulation model (OGCM), with modified physics, is developed which is able to resolve the diurnal cycle of sea surface temperature (SST) and current variability in the upper ocean. It is then validated against a satellite derived parameterization of diurnal SST variability and in-situ current observations. The model is then used to assess rectification of the intraseasonal SST response to the Madden–Julian oscillation (MJO) by the diurnal cycle of SST. Across the equatorial Indo-Pacific it is found that the diurnal cycle increases the intraseasonal SST response to the MJO by around 20%. In the Pacific, the diurnal cycle also modifies the exchange of momentum between equatorially divergent Ekman currents and the meridionally convergent geostrophic currents beneath, resulting in a 10% increase in the strength of the Ekman cells and equatorial upwelling. How the thermodynamic and dynamical impacts of the diurnal cycle effect the mean state, and variability, of the climate system cannot be fully investigated in the constrained design of ocean-only experiments presented here. The second part of this study, published separately, addresses the climate impacts of the diurnal cycle in the coupled system by coupling the OGCM developed here to an atmosphere general circulation model.

This record has no associated files available for download.

More information

Published date: 28 November 2007

Identifiers

Local EPrints ID: 64329
URI: http://eprints.soton.ac.uk/id/eprint/64329
ISSN: 0930-7575
PURE UUID: f77b6cf8-4365-4cec-be92-b49b87e10e3a

Catalogue record

Date deposited: 10 Dec 2008
Last modified: 15 Mar 2024 11:48

Export record

Altmetrics

Contributors

Author: D.J. Bernie
Author: E. Guilyardi
Author: G. Madec
Author: J.M. Slingo
Author: S.J. Woolnough

Download statistics

Downloads from ePrints over the past year. Other digital versions may also be available to download e.g. from the publisher's website.

View more statistics

Atom RSS 1.0 RSS 2.0

Contact ePrints Soton: eprints@soton.ac.uk

ePrints Soton supports OAI 2.0 with a base URL of http://eprints.soton.ac.uk/cgi/oai2

This repository has been built using EPrints software, developed at the University of Southampton, but available to everyone to use.

We use cookies to ensure that we give you the best experience on our website. If you continue without changing your settings, we will assume that you are happy to receive cookies on the University of Southampton website.

×