Premium
The evolution of vortices in vertical shear. II: Large‐scale asymmetries
Author(s) -
Jones Sarah C.
Publication year - 2000
Publication title -
quarterly journal of the royal meteorological society
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.744
H-Index - 143
eISSN - 1477-870X
pISSN - 0035-9009
DOI - 10.1002/qj.49712657008
Subject(s) - vortex , vorticity , barotropic fluid , physics , ocean gyre , anticyclone , asymmetry , geology , radius , mechanics , classical mechanics , atmospheric sciences , subtropics , quantum mechanics , fishery , biology , computer security , computer science
The role of large‐scale asymmetries in the evolution of a tropical‐eye lone‐like vortex in vertical shear on an f ‐plane is investigated. Idealized numerical calculations using a primitive‐equation model are used to illustrate the development of the asymmetries and their role in the evolution of the vortex lilt. The asymmetries develop in the outer region of the vortex, well outside the radius of maximum wind. For the vortex profile used in most of the calculations, the region where the asymmetries develop has anomalously negative potential vorticity (PV) compared with the undisturbed environment, and the flow fields associated with the asymmetries consist of large‐scale anticyclonic gyres. The orientation of the gyres changes with height and they are located on opposite sides of the vortex at lower and upper levels. The influence of the asymmetries on the vortex evolution depends on both the structure and location of the asymmetries and on the orientation of the tilted vortex within the asymmetries. It is hypothesized that the asymmetries arise due to the distortion of the initially symmetric vortex by the horizontally sheared flow associated with the vertical projection of the tilted PV anomaly. Calculations using a barotropic model are presented in support of this hypothesis. The sensitivity of the large‐scale asymmetries to the initial vortex structure is investigated. For a vortex profile in which the tangential wind decreases more slowly with radius, the asymmetries form in a region of positive PV anomaly and the associated flow field contains large‐scale cyclonic gyres. The implications of the large‐scale asymmetries for tropical‐cyclone motion and intensity change are discussed.