Publication Date

2015-11-06

Availability

Open access

Embargo Period

2015-11-06

Degree Type

Thesis

Degree Name

Master of Science (MS)

Department

Meteorology and Physical Oceanography (Marine)

Date of Defense

2015-09-09

First Committee Member

David S. Nolan

Second Committee Member

Brian E. Mapes

Third Committee Member

Stefan Tulich

Abstract

The Intertropical Convergence Zone is characterized by a hierarchy of transients within a large range of spatial and temporal scales that propagate both eastward and westward with varying speeds in synoptic-scale-like waves. Among these tropical structures, the Convectively Coupled Kelvin Waves constitute one of the most significant in terms of contribution to the total ITCZ variability. The first part of this work analyzes the senstivitity of simulated CCKWs to domain size, horizontal resolution and forcing, using the WRF model. The simulations are performed using two types of idealized domains: the “aquachannel” (an oceanic surface with the Earth dimensions, but extending to the latitude of 60 degrees in both hemispheres on the beta plane), and the “aquapatch” (similar configuration as the aquachannel except for its longitudinal extent, which is 1/3 of the former, or approximately 13000 km), with both cases using periodic boundary conditions. The aquapatch is integrated in low and high resolution, and also in a doubly-nested configuration, in which convection is solved explicitly in the innermost grid. The model intercomparison is carried out throughout the use of several techniques such as power spectra, filtering, wave tracking and compositing, and it is extended to some simulations from the “AquaPlanet Experiment”. The second part of this work addresses a topic that has not previously been studied: the life cycle of the CCKWs. A subjective technique is applied to isolate early, mature and decay stages, and then spatial structures as well as propagation speeds of each phase are compared, resulting in some distinctive differences. Moreover, this analysis reveals a “de-coupling” between super cloud clusters and the pressure wave, which is found to be connected with the dissipation of the clusters.

Keywords

CCKW Convectively Coupled Kelvin Waves Aquaplanet Simulation ITCZ

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