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Reply to comments on ‘The influence of rotational frontogenesis and its associated shearwise vertical motions on the development of an upper‐level front’
Author(s) -
Lang Andrea A.,
Martin Jonathan E.
Publication year - 2012
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.2042
Subject(s) - frontogenesis , advection , geostrophic wind , vorticity , potential vorticity , front (military) , geology , differential rotation , climatology , positive vorticity advection , flow (mathematics) , meteorology , geodesy , mechanics , physics , vortex , thermodynamics , mesoscale meteorology , quantum mechanics , magnetic field
Schultz (2012) proposes that our previous arguments regarding the initiation of along‐flow geostrophic cold air advection during the upper frontogenesis process are incomplete. The core of his criticism, and the motivation for his call to include additional diagnostic calculations, hinges upon the assertion that the vertical vorticity can rotate isentropes relative to isohypses. In this response we derive an expression for the rate of change of ∇ ϕ that demonstrates that vorticity rotates ∇ θ and ∇ ϕ equally, in accord with our original statement to that effect. The derived expression also provides motivation to propose a revision of our previous conceptual model, highlighting the role of deformation instead of vorticity in the differential rotation of ∇ θ relative to ∇ ϕ that can contribute to the initiation of along‐flow geostrophic temperature advection. Finally, we present a four‐year synoptic‐climatology suggesting that upper frontogenesis over central North America is, in fact, biased toward environments characterized by northwesterly flow. Copyright © 2012 Royal Meteorological Society