The effect of ozone on the temperature of the upper atmosphere

Abstract

Some interesting papers have recently been published concerning the temperature of the atmosphere above 11 km. It is known experimentally from "ballon sonde" observations that up to 25 or 30 km. the temperature is nearly constant at about 220° K., possibly rising slightly. There are several sources of indirect evidence that above this height the temperature rises again till it is about the same as, or even higher than, at ground level. Lindemann and Dobson have calculated the density of the atmosphere from observations of meteors. From the abnormally high values obtained they conclude that the temperature above 60 km. is of the order of 300° K. They further showed that if the temperature were 220° K., as generally supposed, there would be insufficient heating effect for meteors of less velocity than 19 km. per second to appear, whereas if the temperature were 300° K. the critical velocity would be 12 km. per second. A considerable number of observations give velocities less than 19 km. per second. The author's suggested explanation of the occurrence of a high temperature at such heights was the strong absorption of solar energy in the ozone which has been observed. Whipple refers to the zones of audibility which occur at some distance around big explosions. Assuming a reasonably sharp transition of temperature from 220° to 280° K. at a height of about 60 km., he makes a rough estimate of the minimum radius of the outer zone of audibility. This agrees very well with observations that have been made. Chapman has determined the height and ion concentration of the Heaviside layer by day and by night, and Hulburt claims that the required number of ion would be supplied above 130 km. if the density as calculated on the isothermal hypothesis were multiplied by a factor of 1000. This factor would bring the density into agreement with the results of Lindemann and Dobson. Continuing with the explanation suggested by Lindemann and Dobson, it is proposed in this paper to consider the radiative equilibrium of the upper part of the atmosphere, taking into account the effects, with selective absorption, of water-vapour and ozone. It will be shown that this also leads to a region of high temperature in the neighbourhood of, and above, 60 km.