Theory of Extratropical Cyclones

There is no unique framework for understanding the growth and decay of extratropical cyclones. A number of useful approaches have been pursued in the huge body of literature on the subject during the past fifty years; these are reviewed also by Reed in Chapter 3 of this volume. Studies of the energetics or angular momentum budgets for a box surrounding a developing storm (Section 12.3.4) can, because of their integral nature, provide only a partial description of the processes occurring in the region. Another partial, but interesting, view is obtained by considering the work done by a parcel of air displaced in an otherwise undisturbed environment. Such a discussion ignoring pressure forces and the continuous nature of the medium, cannot be complete but it is in accord with the spirit of synoptic descriptions in terms of the movement of conveyor belts of air, treated by Browning in Chapter 8.