Structure and Temperature of the Stratosphere

Investigations on the structure of the stratosphere during the last year have completely changed our view. Observations have shown that in the lower parts of the stratosphere temperature is increasing very slowly. Lindemann and Dobson used observations on meteors to get results on the density of higher parts. New theoretical values of temperature were found by utilizing the fact that there is a layer of ozone at a height of 40 to 50 km. Investigations of the aurora polaris have shown a difference between rays observed in the layers of the atmosphere in the shadow of the earth and those in sunlight. The spectrum of both kinds of aurorae shows lines of nitrogen but the green line of oxygen seems to decrease between the lower aurorae in the shadow of the earth and the higher ones in the lighted layers. So nitrogen and oxygen must be present up to heights of some hundred km.; the latter may be in a decreasing amount. No lines of helium or hydrogen have been observed. Maris and Epstein found by calculations that the lower parts of the stratosphere up to heights of more than 100 km. need a very long time to restore diffusion equilibrium if mixed. So we can suppose that at least in the lower 100 km. of the stratosphere the composition does not change very much with height. Finally Peterson calculated that a gas originating at the bottom of the atmosphere and leaving it at the top,— for example, according to the results of Jeans, if these parts are too hot,—form at great heights a considerably less amount of the atmosphere than in the case of diffusion equilibrium. The idea of a warm stratosphere at great heights is supported by the observations of sound waves through the stratosphere. Using these facts and the observations of meteors we can calculate the density of the stratosphere with different assumptions. The general result of all methods is that we have very probably an increasing temperature in the stratosphere beginning at a height between 30 and 40 km., no change of composition at least until a height of 150 km., no hydrogen at any height, a slowly decreasing amount of oxygen at heights of some hundred km., and, probably a small amount of helium or water vapor or neon at very great heights. The principal gas at any height is nitrogen