162 R. Mountford Deeley — Cyclones and Climate. 



— to use an incorrect but convenient expression — were exercised by 

 the lightness of the air above the boundary, it ought to draw up 

 the boundary itself as well as the air below it. This is exactly the 

 reverse of what happens; the boundary bulges downwards in the 

 cyclone and upwards in the anticyclone." 



However, the air in the stratosphere and troposphere does not 

 differ as do oil and water. The difference is merely one of 

 temperature, and if the heat of the stratosphere is flowing downwards 

 in the direction of the temperature gradient, faster than the air is 

 rising, then, in spite of rising air, the boundary will bulge down- 

 wards. The bulging downwards of the isotherms right up to the 

 boundary of the troposphere above proves that the air is rising there. 

 To refer again to the letter in Nature by Dines, it will be seen that 

 he says, "But if we postulate an outward radial sucking force acting 

 horizontally on the water just below the common boundary, the 

 water will rise from below at the centre, the common boundary will 

 fall, and the layer of oil will thicken, and this is just what occurs in 

 the layers of air . . . hut I do not see how an outward acceleration can 

 he applied horizontally to the layers of air at the top of the troposphere." 

 The italics are my own. Considering that the downward bulge of 

 the isotherms of the troposphere occurs close up to the stratosphere,, 

 there is no room for such an outward flow, nor has such a flow ever 

 been detected. 



Owing to the large diameter of the cyclone and its thinness, even 

 if there should be a considerable flow inwards the rise of the air over 

 the whole area would be small. When much rain is thrown down in 

 a cyclone it is not due to a general rise of the air, it is due to one 

 current mounting another current locally. It is more reasonable to 

 suppose that the explanation of the downward bulge of the boundary 

 is due to the downward penetration of heat being more rapid than the 

 upward rise of the air. 



It is impossible to account for the existing climatic conditions of 

 the earth on the assumption that the winds are produced entirely 

 by the temperature distribution in the troposphere ; for the direction of 

 the winds of middle latitudes is opposed to tfie temperature gradient. 

 It is the heating of the upper side of the stratosphere (the upper 

 limits of the atmosphere) that results in the winds flowing in the 

 troposphere towards the poles from middle latitudes, in spite of the 

 ground temperature gradient. 



A polar sea, with low land or islands, well connected with the 

 great oceans, would remove to a large extent the present surface 

 temperature gradient, which tends to lessen the force of the ground 

 winds flowing polewards, and would enable the effect of the high 

 temperature of the stratosphere (over the poles) to strengthen the 

 winds flowing towai'ds the poles. These winds would induce ocean 

 currents flowing in the same direction. Indeed, given fairly open 

 water connexions between the Arctic Sea and the great oceans, there is 

 no reason why the Polar area should not be tropical in its climate. 



