The effect of atmosphere-ocean coupling on the sensitivity of the ITCZ to convective mixing

Talib, J. ORCID: https://orcid.org/0000-0002-4183-1973; Woolnough, S.J. ORCID: https://orcid.org/0000-0003-0500-8514; Klingaman, N.P. ORCID: https://orcid.org/0000-0002-2927-9303; Holloway, C.E. ORCID: https://orcid.org/0000-0001-9903-8989. 2020 The effect of atmosphere-ocean coupling on the sensitivity of the ITCZ to convective mixing. Journal of Advances in Modeling Earth Systems, 12 (12), e2020MS002322. 20, pp. https://doi.org/10.1029/2020MS002322

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Abstract/Summary

The Intertropical Convergence Zone (ITCZ) is a discontinuous, zonal precipitation band that plays a crucial role in the global hydrological cycle. Previous studies using prescribed sea surface temperature (SST) aquaplanets show the ITCZ is sensitive to convective mixing, but such a framework is energetically inconsistent. Studies also show that atmosphere‐ocean coupling reduces the sensitivity of the ITCZ to hemispherically asymmetric forcing. We investigate the effect of atmosphere‐ocean coupling on the sensitivity of the ITCZ to convective mixing using an idealized modeling framework with an Ekman‐driven ocean energy transport (OET). Coupling reduces the sensitivity of the ITCZ location to convective mixing due to SST changes. In prescribed‐SST simulations reducing convective mixing promotes a double ITCZ, while in coupled simulations, it increases the meridional SST gradient which promotes an equatorward ITCZ shift. Prescribing OET in additional experiments has a minimal effect on the sensitivity of the ITCZ location to mixing but does increase the sensitivity of the ITCZ intensity by constraining the net‐downward surface energy flux. Decreasing convective mixing increases net‐downward shortwave cloudy‐sky radiation associated with increased latent heat fluxes and an intensified ITCZ. For simulations analyzed the atmospheric energy input framework is inadequate to study ITCZ dynamics due to the contribution of transient eddies to the atmospheric energy transport. Prescribing SST or OET may strengthen the sensitivity of the ITCZ to a change in parameterization or atmospheric forcing. Future modeling studies investigating the precipitation response to such changes should be aware of the potential sensitivity of their results to atmosphere‐ocean interactions.

Item Type:	Publication - Article
Digital Object Identifier (DOI):	https://doi.org/10.1029/2020MS002322
UKCEH and CEH Sections/Science Areas:	Hydro-climate Risks (Science Area 2017-)
ISSN:	1942-2466
Additional Information. Not used in RCUK Gateway to Research.:	Open Access paper - full text available via Official URL link.
Additional Keywords:	Intertropical Convergence Zone, convection, atmosphere‐ocean coupling, aquaplanet, ocean dynamics, tropical rainfall
NORA Subject Terms:	Meteorology and Climatology Atmospheric Sciences
Date made live:	24 Nov 2020 17:07 +0 (UTC)
URI:	https://nora.nerc.ac.uk/id/eprint/528912

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