. Compendium of meteorology. Meteorology. (zflj-5^ rr^^^^ "S"i~ -4 -I 10 sec. 40° Y> 45° 35° 110° NOV. 7,1948 500 mb I500H 100° 40° NOV. 7, 1948 , 1500 H Fig. 11.—Profile of early frontogenesis, November 7, 1948, 1500Z, and part of the SOO-mb map for the same time. Sample eval- uations of 2fii — dvJS-i] below diagram. Upper winds: Half barb 5 m sec"', full barb 10 m sec"', triangular barb 50 m sec"'. following twenty-four hours the new cyclone deepens and moves along the front northeastward. A new field of deformation is active on November 9 along the cold front
. Compendium of meteorology. Meteorology. (zflj-5^ rr^^^^ "S"i~ -4 -I 10 sec. 40° Y> 45° 35° 110° NOV. 7,1948 500 mb I500H 100° 40° NOV. 7, 1948 , 1500 H Fig. 11.—Profile of early frontogenesis, November 7, 1948, 1500Z, and part of the SOO-mb map for the same time. Sample eval- uations of 2fii — dvJS-i] below diagram. Upper winds: Half barb 5 m sec"', full barb 10 m sec"', triangular barb 50 m sec"'. following twenty-four hours the new cyclone deepens and moves along the front northeastward. A new field of deformation is active on November 9 along the cold front of that cyclone and helps maintain the frontal temperature contrast. The described frontogenetical development near the ground conforms with the advective rules set forth by Bergeron [1] and Petterssen [25]. We shall here add a study of the dynamical conditions for isentropic up- gliding in the free atmosphere, which is an important part of the process of frontogenesis. The rate of frontogenesis near the ground is increased considerably if the air of the lower part of the frontal zone is removed by upgliding. The dynamical possibili- ties for that process are considered in Fig. 11, which contains a profile across the zone of frontogenesis dur- ing its early stage on November 7, 1500Z. At that time no clear-cut front was yet discernible on the surface map, but on the 850-mb map there is great crowding of isotherms between the cold air over North Platte and we take into account that condensation Avould begin in such a particle at 700 mb, the ascent from there on would follow the saturation isentrope of 282°, which climbs more steeply than the dry-isentrope and like- wise reaches the tropopause. Actually no single particle undergoes such far-reaching isentropic displacements inside the profile; but the isentropes can still be used as indicators of the direction of the component of stable upgliding (see p. 585), which the particles may have in addition to their much str
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