Use this URL to cite or link to this record in EThOS: http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.602469
Title: Simulations of interacting regions of tropical deep convection coupled by a weak-temperature gradient parameterization of the large-scale circulation
Author: Daleu, Chimene Laure
Awarding Body: University of Reading
Current Institution: University of Reading
Date of Award: 2013
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Abstract:
In the Tropics, the large-scale circulation acts to redistribute density anomalies towards uniform density on isobaric surfaces. This is the weak-temperature gradient (WTG) approximation. In this thesis, a cloud-resolving model (CRM) is used to simulate the interactions between convection and the large-scale circulation which is parameterized using the WTG approximation. As in other WTG studies, the large-scale circulation is derived under the requirement that the instantaneous domain-mean temperature remains close to a reference profile. Over uniform surface conditions, a large-scale descent develops within the simulated column no matter the relaxation profile and the initial conditions. This is similar to the results found in some other WTG studies but not all. A new approach is developed to link two CRMs through the WTG derived large-scale circulation which constrains the domain-mean temperature profiles in the two CRMs to remain close to each other. This extension of the former approach enables the option of closing the heat and moisture budgets. In contrast to the reference column approach, no mean large-scale circulation develops under uniform surface conditions, regardless of the relative size of the columns. The sensitivity to non-uniform surface conditions is similar to that obtained in the simulations that used the reference column if the columns have large difference in areas, but is remarkably weaker for columns of equal areas. The transient evolution of convection is investigated under the new approach. The simulation of the transition is forced by changing the surface forcing. The change in surface forcing drives changes in the strength of the large-scale forcing, which strongly influences the transition. The contributions from the large-scale forcing are equally divided between the heating and moistening effects. The timescale for the transition is examined for different forcing methods. The transition time is much longer when the transition is forced remotely compared to when it is forced locally.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID: uk.bl.ethos.602469  DOI: Not available
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