The Ionosphere

Abstract

SINCE Teisserenc de Bort established the fact that at heights of the order of 10-15 km. the more or less regular fall of air temperature with height ceases, and that for some distance above this change point the temperature is substantially independent of height, it has become customary to treat our atmosphere as divided into two shells. The inner shell, in which convective motion and turbulence are recognised as the dominant physical characteristics, is now called the troposphere, and is separated from the outer shell by the tropopause, the surface at which this well-defined change of the lapse-rate of temperature occurs. So far as the older meteorological means of measurement were concerned, the outer shell, the stratosphere, must—by mere defect of evidence—be regarded as comprising the whole remainder of the sensible atmosphere.