. Compendium of meteorology. Meteorology. 616 MECHANICS OF PRESSURE SYSTEMS upper disturbance associated with the deformation of the upper front which can be followed on the charts in Fig. 8. This deformation of the upper front is associated with the formation of an upper cyclone or a very deep trough. During the process a large part of the cold air is separated from its original source region and flows as a diverging lower current very far to the south. This diverging lower cold current can be seen on the surface inap for November 19 (Fig. 11) in the regions west of the surface cold front. Th
. Compendium of meteorology. Meteorology. 616 MECHANICS OF PRESSURE SYSTEMS upper disturbance associated with the deformation of the upper front which can be followed on the charts in Fig. 8. This deformation of the upper front is associated with the formation of an upper cyclone or a very deep trough. During the process a large part of the cold air is separated from its original source region and flows as a diverging lower current very far to the south. This diverging lower cold current can be seen on the surface inap for November 19 (Fig. 11) in the regions west of the surface cold front. There is no doubt that many "occluded" cyclones on surface maps have never gone through a real process of occlusion although they show the same characteristic etructure as really occluded polar-front perturbations. Obviously a well-marked surface front is not so essen- tial for the development as was generally assumed Fig. 11.—Surface map, 0630 GMT November 19, 1948, three hours later than charts of Figs. 8d and 10c. One more point should be emphasized. By comparison of the consecutive 500-mb charts in Fig. 8 it can be seen that the area of polar air at that level decreases during the process of cyclogenesis and the development of the deep "occluded" surface cyclone. The process of seclusion of the polar air at the 500-mb level thus corre- sponds to the occlusion process in lower layers. In the upper atmosphere the warm air gains area, in the lower atmosphere the cold air gains area. This process corre- sponds to the scheme for release of energy of storms proposed by Margules [33] in his classical ; As a result of the process described here, the upper cold air (for example, at the level of 500 mb) has been 11. The energetics of a similar process of cyclogenesis has recently been studied by Phillips [48]. The main difficulty in applying Margules' ideas on the development of real cyclones depends upon the well-known fact, already emphas
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