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Structure and evolution of Subtropical Cyclone Anita as evaluated by heat and vorticity budgets

Dutra, L. M. M., da Rocha, R. P., Lee, R. W., Peres, J. R. R. and de Camargo, R. (2017) Structure and evolution of Subtropical Cyclone Anita as evaluated by heat and vorticity budgets. Quarterly Journal of the Royal Meteorological Society, 143 (704). pp. 1539-1553. ISSN 1477-870X

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To link to this item DOI: 10.1002/qj.3024

Abstract/Summary

This paper explores the evolution of subtropical cyclone Anita, which occurred near the east coast of Brazil (~19.S-37.W) in March 2010. Thermodynamic and dynamic processes during Anita's lifecycle are investigated using the heat and vorticity budget equations. The cyclone developed with hybrid characteristics and moved anomalously to the southwest where it coupled with an upper level cut-off low during the mature phase. This coupling was the main dynamical mechanism for further cyclone deepening. Anita then remained quasi-stationary about 30.S -47.W for two days due to an upper level dipole pattern which prevented earlier displacement of the upper level low counterpart. When the dipole pattern dissipated, the cyclone moved southeast and underwent extratropical transition whilst merging with a mid-latitude frontal cyclone. Diabatic heating and horizontal temperature advection are found to be essential for the subtropical development. During extratropical transition, it is instead diabatic cooling together with adiabatic cooling and warm air advection that act as the main mechanisms to influence the local temperature tendencies at low levels. Low level cyclonic tendencies were mostly due to convergent flow, and the residual vorticity partially destroyed the vorticity tendencies produced by the divergence term. Moreover, in regions and levels where convection could explain some of the vorticity tendencies, it is found that apparent sinks of cyclonic vorticity were related to negative vorticity due to divergence (i.e., convergent flow), whilst apparent sources were related to positive vorticity due to divergence (i.e., divergent flow).

Item Type:Article
Refereed:Yes
Divisions:Faculty of Science > School of Mathematical, Physical and Computational Sciences > NCAS
Faculty of Science > School of Mathematical, Physical and Computational Sciences > Department of Meteorology
ID Code:69296
Uncontrolled Keywords:Subtropical Cyclones; Heat Budget; Vorticity Budget; Anita; South Atlantic Ocean; Brazil
Publisher:Royal Meteorological Society

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