Title:
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The dynamical response to vertical heating structures in the tropics
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The vertical profile of diabatic heating associated with convection is vitally important to the largescale
tropical circulation. Systematic errors in diabatic heating distributions in models are considered
to be a primary cause in their errors in representing the large-scale mean circulation and
tropical variability in the Tropics. Much attention has been given to the vertical heating structure
of the Madden-Julian Oscillation (MJO) in recent years to understand the fundamental physics of
the MJO and why many general circulation models struggle to simulate a robust MJO.
In this thesis, estimates of vertical diabatic heating structures from reanalysis datasets and Tropical
Rainfall Measuring Mission (TRMM) latent heating algorithms are used to understand how
variations in the detailed structure of the heating influence the structure in the dynamical response
in the Tropics. As pan of this study, the role of the vertical structure of the heating of the MJO
to the dynamical response is investigated by integrating a primitive equations model with vertical
anomalous diabatic heating structures associated with the MJO. In particular, the role of a vertical
tilt in the heating, which has been identified in three reanalysis datasets. is investigated in relation
to the moisture convergence and energetics.
An eastward phase shift of the moisture convergence of approximately 1 day directly associated
with the vertical anomalous heating structure of the MJO was found for each of the reanalysis
heatings. As a consequence of this phase shift, a surplus of moisture convergence over the
anomalous heating was generated in regions ahead of the MIO convection centre indicating a
pre-moistening of tlle atmosphere prior to deep convection. It was demonstrated that both a leading
mid to shallow congestus heating and a lagging stratiform heating relative to the main MJO
convection were important in contributing to the phase shift in the moisture convergence. Both
these vertical heating structures may therefore be critical to the maintenance of the MJO through
the warm pool region. The response to the two the heatings from the TRMM products showed no
phase shift in the moisture convergence relating to the vertical heating structure of the MJO. This
was due to no observable vertical tilt in the heating structure.
There is increased generation of eddy entropic potential energy and conversion of that energy
into eddy kinetic energy through the MJO cycle associated with the vertical anomalous heating
structure of the MIO. This was related to stronger heating in the mid-troposphere generating
stronger eddy potential energy (EPE) between 600 and 400 hPa, which exceeded the rcduction in
generation of EPE in the planetary boundary layer (PBL).
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