R. Mountford Deeley — Cyclones and Climate. 161 



Such are the facts, as near as they are known, with regard to the 

 temperature distribution in the atmosphere. It remains to consider 

 the cause of this peculiar distribution and its bearing upon the theory 

 of cyclones. 



The temperature of the earth's surface and of the atmosphere is 

 much above that of space, owing to the radiations received from the 

 sun, and also very probably owing to the bombardment of cosmic 

 matter to which the atmosphere is subjected at its upper limit. Not 

 only do we receive heat from the sun in the form of heat and light 

 rays and X radiations, but it has been shown that electrons are 

 being shot out from the sun at enormous velocities. ' These electrons, 

 when they reach the magnetic field of the earth, are captured and 

 are directed in long spirals towards the poles, where they give rise, 

 among other phenomena, to the auroral lights. Meteors, both large 

 and small, strike the atmosphere at high velocities and heat it, and 

 there would seem to be pencils of high velocity cosmic matter, which 

 are also arrested by the atmosphere. 



The energy thus directed earthwards is mainly either arrested by 

 the upper atmosphere or by the lower portion of the troposphere 

 and the earth's surface. The radiant energy which is arrested by 

 the upper atmosphere heats the air, and this heat passes downwards 

 to the lower portions of the stratosphere by radiation and con- 

 duction, not by convection. The undulations, to which the clear 

 atmosphere is transparent, and which pass through it, are intercepted 

 by the earth's surface and by clouds, water vapour, and carbonic 

 acid. This lower warmed stratum of air then rises and cools by 

 expansion, with the result that the troposphere assumes the con- 

 dition of convective equilibrium. 



Balloon ascents show that above cyclones the air of the stratosphere 

 is warmer than it is above anti-cyclonic areas, and that the lower 

 boundary of the stratosphere is lowest near cyclonic centres. But in 

 Fig. 2 the air is shown to be rising in the centre of the cyclone, and 

 it has been suggested that if the air is rising in such areas the line 

 B B should bulge upwards. 



As already remarked," Aitkin, in a paper read before the Royal 

 Society of Edinburgh in June, 1916, showed that although the core 

 of a cyclone is colder than the surrounding regions of high pressure, 

 yet the air in the cyclone is lighter. This low density is due to the 

 air being under a lower pressure, and this more than compensates 

 for the lower temperature ; so that though the air in cyclones is 

 colder, yet it is lighter than the surrounding air, and the central 

 core, therefore, tends to ascend both in the troposphere and the 

 stratosphere. 



In Nature for January 30, 1919, Dines remarks : "Mr. Deeley's 

 suggestion {Nature, January 16, p. 385) that the cyclone is caused 

 by the high temperature of the stratosphere does not seem to me to 

 be feasible for the following reason: Owing to the temperature 

 inversion, or, at least, to the cessation of the lapse of temperature 

 with height, the boundary between the troposphere and stratosphere 

 is, in general, perfectly definite, as definite almost as the boundary 

 between oil and water would be. If then any sort of sucking action 



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