The Role of Shearwise and Transverse Quasigeostrophic Vertical Motions in the Midlatitude Cyclone Life Cycle
نویسنده
چکیده
The total quasigeostrophic (QG) vertical motion field is partitioned into transverse and shearwise couplets oriented parallel to, and along, the geostrophic vertical shear, respectively. The physical role played by each of these components of vertical motion in the midlatitude cyclone life cycle is then illustrated by examination of the life cycles of two recently observed cyclones. The analysis suggests that the origin and subsequent intensification of the lower-tropospheric cyclone responds predominantly to column stretching associated with the updraft portion of the shearwise QG vertical motion, which displays a single, dominant, middle-tropospheric couplet at all stages of the cyclone life cycle. The transverse QG omega, associated with the cyclones’ frontal zones, appears only after those frontal zones have been established. The absence of transverse ascent maxima and associated column stretching in the vicinity of the surface cyclone center suggests that the transverse plays little role in the initial development stage of the storms examined here. Near the end of the mature stage of the life cycle, however, in what appears to be a characteristic distribution, a transverse ascent maximum along the western edge of the warm frontal zone becomes superimposed with the shearwise ascent maximum that fuels continued cyclogenesis. It is suggested that use of the shearwise/transverse diagnostic approach may provide new and/or supporting insight regarding a number of synoptic processes including the development of upper-level jet/front systems and the nature of the physical distinction between type A and type B cyclogenesis events.
منابع مشابه
Lower-Tropospheric Height Tendencies Associated with the Shearwise and Transverse Components of Quasigeostrophic Vertical Motion
The recent suggestion that lower-tropospheric cyclogenesis is predominantly a result of column stretching associated with the updraft portion of the shearwise quasigeostrophic (QG) vertical motion is quantified through direct calculation of 900-hPa height tendencies via the QG vorticity equation. Comparison of the separate lower-tropospheric height tendencies associated with the shearwise and t...
متن کاملNOTES AND CORRESPONDENCE On the Deformation Term in the Quasigeostrophic Omega Equation
It is a common diagnostic, synoptic practice to consider the Trenberth–Sutcliffe approximation to the quasigeostrophic (QG) omega equation, which relates upward vertical motion to regions of cyclonic vorticity advection by the thermal wind. Use of this approximate form of the QG omega equation requires the neglect of the so-called deformation term, which is often described as important only in ...
متن کاملDynamics and Thermodynamics Analysis of Tropical Cyclone Haiyan
Tropical cyclone Haiyan (TCH) that formed over the West Pacific Ocean during 3-11 November 2013 has been investigated using three datasets produced by Japan Meteorology Agency, ECMWF and NCEP. Strength of TCH has been studied using two synoptic parameters of 10-m wind velocity and mean sea level pressure (MSLP). Following, three dynamic parameters including vertical wind shear (VWSH) vector, he...
متن کاملQuasigeostrophic Forcing of Ascent in the Occluded Sector of Cyclones and the Trowal Airstream
A numerical model-based analysis of the quasigeostrophic forcing for ascent in the occluded quadrant of three cyclones is presented based upon a natural coordinate partitioning of the Q vector into its alongand acrossisentrope components, Qs and Qn, respectively. The Qn component describes the geostrophic contribution to the rate of change of the magnitude of =pu (traditional frontogenesis), wh...
متن کاملNonsupercell Tropical Cyclone Tornadoes: Documentation, Classification and Uncertainties
An ingredients-based approach (e.g., Johns and Doswell 1992) is used in the operational prediction of tornado threat, regardless of whether the favorable environment results from midlatitude or tropical perturbations. Since the majority of tropical cyclone (TC) tornadoes are associated with supercells (Edwards et al. 2012a; hereafter E12), the forecaster typically can focus on the same ingredie...
متن کامل