. Compendium of meteorology. Meteorology. gliding begins above that line. Moreover, we find that the dry-isentropes indicate a downgliding with a hori- zontal component across the front from cold to warm, while the upgliding along saturation isentropes remains almost parallel to the frontal slope. The frontal profile therefore must begin to bulge forward from cold to warm in the lower layers while remaining rather unchanged higher up. That is what happens when the apex of the frontal wave goes by, as will be discussed in connection with the maps in Fig. 14. The anticyclonic shear south of the
. Compendium of meteorology. Meteorology. gliding begins above that line. Moreover, we find that the dry-isentropes indicate a downgliding with a hori- zontal component across the front from cold to warm, while the upgliding along saturation isentropes remains almost parallel to the frontal slope. The frontal profile therefore must begin to bulge forward from cold to warm in the lower layers while remaining rather unchanged higher up. That is what happens when the apex of the frontal wave goes by, as will be discussed in connection with the maps in Fig. 14. The anticyclonic shear south of the westwind maxi- mum has growTi to the state of dynamic instability as shown in Fig. 12 by means of the differentiation of Vg along the 333° isentrope. Shears rather close to the in- stability limit also extend down to the 500-mb level and make possible the rather large and systematic wind component towards low pressure observed on the 500- mb map southeast of the jet stream. Figure 13 shows a profile across the cold front from Dodge City (Kansas) to Maxwell Field (Alabama) on November 9, 1500Z. The corresponding sea-level and 850-mb maps are to be found in Fig. 10. The profile shows that strong horizontal temperature gradients have formed all the way to the top of the diagram. The frontogenetical process by horizontal advection has actually been operating through the whole troposphere (in Fig. 14 the resulting frontal zone shows up well even at the 300-mb level). The inclination of the frontal shape of the profile can be understood as the result of the bulging forward of the lower portion of the cold wedge after the passage of the frontal wave apex. The. 'Z d-q 37° SS" NOV. 9,1948, 1500 Z 33° Fig. 13.—Profile of the cold front on November 9, 1948, 1600Z. Sample evaluations of 20^ — dv„/dri below diagram. nongeostrophic downgliding responsible for that process was found to be dynamically justified from the study of the frontal profile 24 hours earlier, v^dva/dx 4-.
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