The energy budget of the stratosphere over North America during the warming of 1957

Abstract

The large and rapid changes in kinetic energy and in total potential energy of the lower stratosphere (100 to 25 mb) during the warming of mid-January to mid-February, 1957, have been investigated in terms of energy transport and generation processes. These processes are represented by the corresponding terms in the balance equations for kinetic and total potential energy. The terms were evaluated using the 100-, 50-, and 25-mb values of geopotential, temperature, the geostrophic wind components, and adiabatic vertical motion at each point of a grid covering most of the North American continent and the adjacent North Atlantic. A limited atmospheric region was considered, which exchanged energy with the surrounding atmosphere through the vertical boundaries as well as through the upper and lower boundary pressure surfaces. Terms in the kinetic energy budget explicitly involving existing kinetic energy were found to be negligible in comparison with the other terms. Conversion of energy was from kinetic to potential energy throughout most of the period. The contributions to energy changes due to generation of kinetic energy at the upper and lower boundaries and net vertical flux of enthalpy are shown to be quite large.