Foehn Wind Cyclo-Genesis

Abstract

According to modern theories regions of cyclo-genesis arise where convergent flow occurs between air masses of different characteristics, provided significant temperature differences exist. Such a flow tends to form a discontinuity surface or front between the masses and to produce large amounts of potential energy of mass distribution along the frontal zone. If the conditions for stable equilibrium are not rigidly maintained along the front, the colder mass may move forward into the warmer current or vice versa. In any case there occurs a compensating flow in the adjacent mass, the whole process giving rise to the genesis of a cyclonic disturbance. The kinetic energy of the resulting cyclone is provided to a large measure by the initial potential energy of mass distribution; although, of course, the heat of condensation liberated in the event that the warm mass is particularly moist furnishes a minor portion. A detailed discussion of the formation, maintenance, occlusion and final death of the cyclone is beyond the scope of the present paper. I merely wish to emphasize at this point the importance of convergent flow in constrasting air masses for furnishing the potential energy necessary for the genesis and subsequent maintenance of the extra-tropical cyclone.