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Dynamics of a low‐level jet observed during the Fronts 87 experiment
Author(s) -
Kotroni V.,
Lemaitre Y.,
Petitdidier M.
Publication year - 1994
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.49712051604
Subject(s) - mesoscale meteorology , geology , baroclinity , outflow , jet (fluid) , mesoscale convective system , convective instability , convection , wind shear , climatology , frontogenesis , meteorology , instability , cold front , atmospheric sciences , mechanics , physics , wind speed
A study of the internal dynamics of a low‐level jet, its role on the frontal discontinuity evolution, and its relevance to the organization of convection at mesoscale and small scale is presented. The low‐level jet studied is associated with an active cold front that was observed during the French—British co‐operative field experiment Fronts 87. The originality of the present low‐level‐jet description lies in the fact that it is observed not only by means of soundings but also by means of a new tool for mesoscale meteorology observations, a wind profiler (stratospheric—tropospheric UHF radar). The high resolution of the wind‐profiler data in both time and height allows one to assess, in precipitating as well as in clear‐sky areas, a detailed image of the low‐level jet and the associated mesoscale and convective‐scale circulations. The comparison between observations and predictions of various theories provides information on the physical mechanisms responsible for the initiation and maintenance of the observed mesoscale features. The flow resulting from the presence of the low‐level jet produces inertial acceleration and baroclinic symmetric instability which lead to a narrow mesoscale line of sloping motions. Moreover, the interaction of the cold surface outflow with the low‐level vertical shear below the jet maximum is found to be crucial in the intensification and maintenance of the observed narrow cold‐frontal rainband.