On fluctuations of pressure and temperature in the atmosphere

Abstract

The paper contains a critical survey of the problem of pressure and temperature fluctuations in the atmosphere. If we exclude non-adiabatic processes, then changes of pressure and temperature are essentially due to horizontal and vertical movements in the atmosphere. The vertical distribution of pressure over the globe shows that horizontal movements (advection) can give rise to large changes of pressure especially in the middle latitudes. The problem of identifying the layer or layers in which addition or removal of mass has taken place due to advection, from the data furnished by aerological ascents over a station has been tackled by a number of investigators. Rossby considered the general problem of advection in several layers of an atmospheric air column, but his theory when applied to practical cases yields results which are often unreasonable. Ertel and Sjan-zsi-Li considered the same problem some years later and claimed to have discovered a fundamental error in Rossby’s theory. In the present paper this problem is considered at some length. It is shown that Rossby’s theory is quite correct under the assumption on which it is built up while the theory of Ertel and Li is not valid for cases of arbitrary advection. It is shown that the neglect of horizontal advection of pressure and horizontal convergence and divergence of wind velocity is responsible for the obviously unreasonable results furnished by Rossby’s theory when applied to actual examples.