A model of Rossby waves linked to submonthly convection over the eastern tropical Pacific

Matthews, Adrian J. ORCID: https://orcid.org/0000-0003-0492-1168 and Kiladis, George N. (2000) A model of Rossby waves linked to submonthly convection over the eastern tropical Pacific. Journal of the Atmospheric Sciences, 57 (23). pp. 3785-3798. ISSN 0022-4928

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Abstract

Equatorward-propagating wave trains in the upper troposphere are observed to be associated with deep convection over the eastern tropical Pacific on the submonthly time scale during northern winter (Fig. 1). The convection occurs in the regions of ascent and reduced static stability ahead of cyclonic anomalies in the wave train. In this study an atmospheric primitive-equation model is used to examine the roles of the dry wave dynamics and the diabatic heating associated with the convection. Many features of a dry integration initialized with a localized wave train in the African--Asian jet on a three-dimensional climatological basic state quantitatively agree with the observations, including the zonal-wavenumber 6--7 scale of the waves, the time period of approximately 12 days and the cross-equatorial Rossby wave propagation over the eastern Pacific. There is ascent and reduced static stability ahead of the cyclonic anomalies, consistent with the interpretation of the waves forcing the convection. The spatial scale of the waves appears to be set by the basic state; baroclinic growth upstream in the Asian jet favors waves with zonal-wavenumber 6. On reaching the Pacific sector, lower-wavenumber components of the wave train are not refracted so strongly equatorward, while higher-wavenumber components are advected quickly along the Pacific jet before they can propagate equatorward. Once over the Pacific, the wave train approximately obeys barotropic Rossby wave dynamics. The observed lower-tropospheric anomalies include an equatorial Rossby wave that propagates westward from the region of cross-equatorial wave propagation and tropical convection. However, this equatorial Rossby wave is not triggered directly by the equatorward-propagating wave train, but appears in a separate integration as a forced response to the observed diabatic heating associated with the tropical convection.

Item Type:	Article
Faculty \ School:	Faculty of Science > School of Mathematics Faculty of Science > School of Environmental Sciences
UEA Research Groups:	Faculty of Science > Research Groups > Centre for Ocean and Atmospheric Sciences Faculty of Science > Research Groups > Volcanoes@UEA (former - to 2018) Faculty of Science > Research Groups > Marine and Atmospheric Sciences (former - to 2017) Faculty of Science > Research Groups > Meteorology, Oceanography and Climate Dynamics (former - to 2017) Faculty of Science > Research Groups > Climate, Ocean and Atmospheric Sciences (former - to 2017)
Depositing User:	Vishal Gautam
Date Deposited:	10 Mar 2011 12:43
Last Modified:	15 Dec 2022 01:55
URI:	https://ueaeprints.uea.ac.uk/id/eprint/20943
DOI:	10.1175/1520-0469(2000)057<3785:AMORWL>2.0.CO;2

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