Abstract
Considering the variation with longitude of the basic current of westerlies in the upper troposphere, the problem of baroclinic disturbance is discussed on assumptions of non-divergent and adiabatic motion. It is shown from this investigation that a speed of trough is almost equal to the Rossby's result, and when the decreasing rate of the basic current with longitude exceeds a certain critical value, the disturbance becomes unstable.
