(Massachusetts Institute of Technology and Woods Hole Oceanographic Institution, 1942-01)
Petterssen, Sverre; Austin, James Murdoch
Soon after the discovery of the polar front, it was realized that fronts were subject
to processes which either increased or diminished their intensity. Thus, fronts may form in fields where the distributiori of the meteorological elements is continuous; and, in other cases, fronts may dissolve and develop into a field of continuous distribution of the
various elements.
The processes which lead to the formation of a front or the increase in intensity of an
existing front, are called jrontogenetical processes; and the processes which lead to the
dissolution of fronts are calledjrontolytical processes.
In theoretical treatments of fronts it has been customary to simplify the problem by
assuming that a frontal surface is a mathematical discontinuity, and doubts have been
raised against the validity of this simplification. Petterssen has shown that both the
dynamic and the kinematic boundary conditions that hold for perfect discontinuities
hold also for layers of transition of finite thickness within which the meteorological elements
vary continuously. We are, therefore, justified in treating frontal surfaces and
fronts as either strict discontinuities or as finite layers of transition. Frontogenesis may
therefore be defined as the process that tends to create a surface of discontinuity in the
atmosphere. Whether or not this process results in a strict discontinuity is immaterial.
