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Mid‐tropospheric frontogenesis
Author(s) -
Bosart L. F.
Publication year - 1970
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.49709640908
Subject(s) - frontogenesis , troposphere , baroclinity , radiosonde , potential vorticity , climatology , vorticity , atmospheric sciences , geology , thermal wind , meteorology , environmental science , wind shear , vortex , mesoscale meteorology , physics , wind speed , oceanography
Mid‐tropospheric frontogenesis is investigated for a case study in which special three‐hourly rawinsonde data are available. Isentropic analyses are made by objective means. Isentropic trajectories lead to the three‐dimensional description of the velocity field in space and time. Potential vorticity is used to check trajectories and to distinguish stratospheric from tropospheric air. Miller's frontogenesis equation is applied in two and three dimensions to an intensifying mid‐tropospheric baroclinic zone. Frontogenetical and frontolytical regions arising from twisting, horizontal confluence, vertical shear of vertical velocity and ageostrophic contributions are delineated. Typical frontogenesis magnitudes are 2°C (100 km) −1 (3 hr) −1 and 2°C (km) −1 (3 hr) −1 in two and three dimensions respectively. Previous observations of the extrusion of stratospheric air into the troposphere are confirmed. A synoptic sequence common to many occurrences of mid‐tropospheric frontogenesis is described. A simple explanation is given of the initial development of a thermally indirect circulation accompanying the early frontogenesis. Mid‐tropospheric frontogenesis seems to accompany the extrusion of stratospheric air into the troposphere during which momentum, potential vorticity, ozone and radioactivity are transported downward and southward.